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# 37th International Cosmic Ray Conference – The Astroparticle Conference –

The ICRC Conference Series has been organised biennially since 1947 under the auspices of the International Union of Pure and Applied Physics (IUPAP) and is the largest conference on Astroparticle Physics, bringing together the different topics of the field.

The main topics are Cosmic Ray Physics, Gamma-Ray Astronomy, Neutrino Astronomy & Neutrino Physics, Dark Matter Physics and Solar and Heliospheric Physics. Additional new topics in the 2021 conference are Multi-messenger Astronomy and Outreach & Education. Broad reviews and recent scientific results, related theory and modelling, experimental methods, techniques and instrumentation will be presented. The ICRC 2021 will be a prime forum to learn about news and developments in Astroparticle Physics and to appreciate the links between its topics.

Due to the COVID-19 pandemic, this year’s ICRC will be held entirely online. The format is therefore somewhat unusal. We hope to provide an experience to the standards of past ICRCs. To make full use of the online format, all contributions will be made available one week before the official start of the conference (abstracts and proceedings paper for all contributions; presentation slides and pre-recorded presentation videos for the 12-min talks,  posters and pre-recorded 2-min flash talks for poster contributions). This allows browsing through the contributions, commenting and asking questions, and coming prepared to the more discussion-like, topical parallel sessions.

Yours Sincerely,

Johannes Knapp
Chair of the Local Organising Committee

Contact
• Monday, July 12
• Plenary: Opening 01

#### 01

• 1
Pre-Opening

Organizational Details

Speaker: Johannes Knapp (DESY, Zeuthen)
• 2
Opening
Speakers: Johannes Knapp (DESY, Zeuthen), Sunil K. Gupta (TIFR, Mumbai)
• 3:30 PM
Break
• Plenary: Highlight 01 01

#### 01

Convener: Anna Franckowiak (DESY)
• 3
AMS Highlights

In nine years on the International Space Station, the Alpha Magnetic Spectrometer (AMS) has collected more than 170 billion cosmic rays measuring with unprecedented precision different components of the charged cosmic rays up to few TeVs. This includes fluxes of positrons, electrons, antiprotons, protons, and nuclei from helium to silicon and beyond. A summary of the latest results will be shown. Results on time variation of cosmic ray fluxes associated with solar activity on different time scales will be presented.

Speaker: Javier Berdugo (CIEMAT)
• 4
Neutrino Telescope in Lake Baikal: Present and Nearest Future

The progress in the construction and operation of the Baikal Gigaton Volume Detector inLake Baikal is reported. The detector is designed for search for high energy neutrinos whose sources are not yet reliably identified. It currently includes over 2000 optical modules arranged on 56 strings, providing an effective volume of 0.35 km3 for cascades with energy above 100 TeV. We review the scientific case for Baikal-GVD, the construction plan, and first results from the partially built experiment which is currently the largest neutrino telescope in the Northern Hemisphere and still growing up.

Speaker: Zhan-Arys Dzhilkibaev (Institute for nuclear research Moscow)
• 5
Fermi LAT and GBM collaboration results on GRB 200415A.

Magnetars are neutron stars with the strongest magnetic fields known in the Universe, with an intensity up to a thousand times higher than typical neutron stars. Rarely, magnetars can produce enormous eruptions, called Magnetar Giant Flares (MGF), consisting of short-duration bursts of hard X-rays and soft gamma rays – a bright and variable initial spike lasting a few tenths of a second and a significantly dimmer pulsating tail lasting a few hundred of seconds that can only be detected from MGFs within our close to our galaxy. On April 15, 2020, a short bright burst of MeV gamma rays triggered the Gamma-Ray Burst Monitor (GBM) aboard the Fermi spacecraft, called GRB 200415A and localized by the InterPlanetary Network (IPN) inside the disk of the nearby Sculptor galaxy. 19 seconds later, and for nearly 300 seconds, the Large Area Telescope (LAT) detected GeV photons in spatial coincidence with the signal at lower energies. In this talk we present the recently published results of the GBM and LAT analysis on GRB 200415A. Our detailed analysis shows that the low-energy emission has very peculiar properties typically observed in flares from nearby magnetars, while the GeV detection is consistent with the IPN localization and spatially associated with the Sculptor galaxy. Hence, we infer that gamma rays likely originated with the MGF in Sculptor, and not from a cosmological gamma-ray burst, and we suggest that the GeV signal is generated by an ultra-relativistic outflow that first radiates the prompt MeV-band photons. This discovery represents the first detection of the high-energy emission from a MGF and proves that extragalactic MGFs may indeed disguise as short GRBs and constitute a small fraction of current short GRB samples.

Speaker: Niccolo di Lalla
• 5:30 PM
Break
• Discussion: 01 Magnetic Fields and CR Propagation | CRI 03

#### 03

• 6
Extragalactic magnetic fields and directional correlations of ultra-high-energy cosmic rays with local galaxies and neutrinos

Deflections of ultra-high-energy cosmic rays (UHECRs) in extragalactic magnetic fields (EGMFs) decrease the expected directional correlations between UHECR arrival directions on the one hand and UHECR source positions and neutrino arrival directions on the other hand. We use the recently observed correlation between UHECRs and local star-forming galaxies by the Pierre Auger Observatory to put limits on the EGMFs between these galaxies and the Milky Way [1]. In addition, using the same methods, we investigate whether correlations between UHECR and neutrino arrival directions can be expected [2]. We take into account deflections in extragalactic and Galactic magnetic fields, energy-loss interactions with background photon fields and UHECR spectrum and composition measurements. For a source density of star-forming galaxies we show that strong EGMFs ($B > 10$ nG Mpc$^{1/2}$) are required to reproduce the level of anisotropy that Auger has observed. For more numerous sources, e. g. spiral galaxies, weaker EGMFs are allowed. However, this would suggest that UHECR acceleration occurs in many regular galaxies, which is rather difficult to motivate. We demonstrate that even for the weakest EGMFs the non-observation of neutrino multiplets strongly constrains the possibility to find neutrino-UHECR correlations. For star-forming galaxies, or more numerous sources, no neutrino multiplets or neutrino-UHECR correlations are currently expected.

--

[1] A. van Vliet, A. Palladino, A. Taylor and W. Winter, in preparation.
[2] A. Palladino, A. van Vliet, W. Winter and A. Franckowiak, Mon. Not. Roy. Astron. Soc. 494, 4255 (2020).

Speaker: Dr Arjen Rene van Vliet (Z_THAT (Theoretische Astroteilchenphysik))
• 7
Faraday rotation constraints on large scale Halo model

The global structure of the magnetic field inside the disk of our Galaxy is quite well described by dynamo action and constrained by Faraday rotation measurements. The Halo, on the other hand, is much more of an enigma. Other face-on spiral galaxies show spiral magnetic structures in their disk, like the Milky Way, showing that our magnetic field is a rather typical feature for such class of galaxies. Furthermore, RM-synthesis of CHANGE-ES observations shows an increasing number of edge-on spiral galaxies presenting X-shaped structures surrounding the disk and extending orderly to distances of up to tens of kpc. Although the 4-dimensional topology of those magnetized halos and their physical nature is still unclear, they hint to the strong possibility that our galaxy also has a large and well organized magnetized Halo. Current models for the Milky Way's magnetic field extend very little out of the galactic plane and do not consider an extended, topologically well-organized field in the Halo. In this work, conceptually motivated by the possible existence of a Parker type galactic outflow, we propose a simple Archimedean-like field, for an extended Halo magnetic field. We add this component to a simple disk magnetic field, in order to model the Faraday rotation signal of extragalactic sources as observed on Earth and compare the results to published maps of Faraday rotation. We show that an extended magnetic field in the Halo is not only compatible with the observed Faraday rotation measurements, but it is actually favored by them.

Speaker: Dr Thomas Fitoussi (Karlsruhe Institute of Technology - IAP (IKP))
• 8
Magnetic field generation by the first cosmic rays

We recently proposed that cosmic rays are first accelerated at the redshift of z~ 20 by supernova remnants of first stars without the large scale magnetic field. In this talk, we are going to talk about the large scale magnetic field generation by the first cosmic rays. We show that even though the current and charge neutralities are initially satisfied, the current neutrality is eventually violated if there is an inhomogeneity, so that the magnetic field is generated. In addition, we propose a new driving mechanism for the Biermann battery in an inhomogeneous plasma with streaming cosmic rays. We demonstrate the new generation mechanisms of the magnetic field by conducting three-fluid plasma simulations and particle in cell simulation. We propose that the first cosmic rays generate the magnetic field with a large scale at the redshift of z~20.

Speaker: Yutaka Ohira (The University of Tokyo)
• 9
Magnetic field structure in halos of star-forming disk galaxies

The CHANG-ES (Continuum HAlos in Nearby Galaxies - an EVLA Survey) project has observed a sample of 35 edge-on spiral galaxies with the JVLA in C- and L-band. The observations in all Stokes parameters provide polarization information and for 16 galaxies with extended emission it is possible to describe the large scale magnetic field structure in their halos. We exemplify a few of these objects and demonstrate the properties of the mean large-scale magnetic field structure as a result from a stacking experiment. We briefly compare the results with the Milky Way and discuss implications for the transport of cosmic ray electrons.

Speaker: Prof. Ralf-Jürgen Dettmar (Ruhr University Bochum)
• 10
Phenomenology of CR-scattering on pre-existing MHD modes

We present the phenomenological implications of the micro-physics of cosmic-ray (CR) diffusion as resulting from particle scattering onto the three modes in which Magneto-Hydro-Dynamics (MHD) cascades are decomposed. We calculate the diffusion coefficients from first principles based on reasonable choices of the physical quantities characterizing the different environments of our Galaxy, namely the Halo and the Warm Ionized Medium, and implement for the first time these coefficients in the DRAGON2 numerical code. Remarkably, we obtain the correct propagated slope and normalization for all the charged species taken into account, without any ad-hoc tuning of the transport coefficients. We show that fast magnetosonic modes dominate CR confinement up to $\sim 100 \, \mathrm{TeV}$; Alfvénic modes are strongly subdominant due to the anistropy of the cascade (in agreement with previous findings) up to rigidities in the sub-PeV domain, where their contribution may show up as a spectral feature, potentially observable in the upcoming years. We also find that such framework cannot be responsible for CR confinement below $\sim 200 \, \mathrm{GeV}$, possibly leaving room for an additional confinement mechanism, and that the Kolmogorov-like scaling of the $B/C$ ratio cannot be reproduced. Therefore this scaling might not be the imprint of the pre-exisiting turbulence spectrum.

Speaker: Ottavio Fornieri (DESY Zeuthen)
• 11
CRPropa 3.2: a framework for high-energy astroparticle propagation

The landscape of high- and ultra-high-energy astrophysics has changed in the last decade, in large part owing to the inflow of data collected by cosmic-ray, gamma-ray, and neutrino observatories. At the dawn of the multimessenger era, the interpretation of these observations within a consistent framework is important to elucidate the open questions in this field. CRPropa 3.2 is a Monte Carlo code for simulating the propagation of high-energy particles in the Universe. This new version represents a step further towards a more complete simulation framework for multimessenger studies. Some of the new developments include: cosmic-ray acceleration, support for particle interactions within astrophysical sources, full Monte Carlo treatment of electromagnetic cascades, improved ensemble-averaged Galactic propagation, and a number of technical enhancements. Here we present some of these novel features and some applications to gamma- and cosmic-ray propagation.

Speaker: Rafael Alves Batista (Radboud University)
• Discussion: 19 SEP Acceleration and Propagation | SH 07

#### 07

• 12
Turbulent Reduction of Drifts for Solar Energetic Particles

Particle drifts perpendicular to the background magnetic field are proposed by some authors as an explanation for the very efficient perpendicular transport of solar energetic particles (SEPs). This process, however, competes with perpendicular diffusion caused by magnetic turbulence, which will also disrupt the drift patterns and reduce the efficiency of drift effects. The latter phenomenon is well known in cosmic ray studies, but not yet considered in SEP models. Additionally, SEP models which do not include drifts, especially for electrons, use turbulent drift reduction as a justification of this omission, without critically evaluating or testing this assumption. We present the first theoretical step for a theory of drift suppression in SEP transport. This is done by deriving the turbulence-dependent drift reduction function with a pitch-angle dependence, as applicable for anisotropic particle distributions, and by investigating to what extent drifts will be reduced in the inner heliosphere for realistic turbulence conditions and different pitch-angle dependencies of the perpendicular diffusion coefficient.

Speaker: Jabus van den Berg (Centre for Space Research, North-West University, Potchefstroom, South Africa)
• 13
Anomalous Transport and Acceleration of Energetic Particles

The theoretical description of energetic particle transport near interplanetary shocks in the inner and outer Heliosphere and in other astrophysical contexts usually follows a diffusive paradigm. By means of scattering of particles at magnetic irregularities upstream and downstream of the shock, particles can be moved back and forth across the shock discontinuity and gain energy, forming power-law energy spectra. In recent years, it has become clearer that this scattering does not necessarily adhere to a Gaussian diffusive picture, i.e. it can be an anomalous transport process, possibly caused by inhomogeneous structures in the plasma turbulence, such as small-scale flux tubes. This anomalous transport is, as a first approximation, often characterized by a non-linear behavior of the mean-square displacement of particles. Here we discuss the theory and implications of this assumption in the context of interplanetary shocks. In particular, we will address how this behaviour can be modeled with non-Gaussian probability distributions together with a stochastic differential equation scheme.

Speaker: Frederic Effenberger (Ruhr-University Bochum)
• 14
Electron acceleration parallel and perpendicular to overshoot magnetic field in quasi-perpendicular collisionless shock

Energetic, non-thermal electrons are commonly observed both upstream and immediately downstream from the Earth’s quasi-perpendicular bow shock (Gosling, 1989). Upstream the energetic electrons are generally field-aligned beams, whereas downstream the flux of them is generally most intense in the direction perpendicular to the magnetic field. However, the acceleration mechanism of these electrons remains unclear. Here, we show a new type of electron acceleration process at an overshoot downstream of a quasi-perpendicular collisionless shock, by performing a one-dimensional particle-in-cell (PIC) simulation. The shock parameters are as follows. The Alfven Mach number is 7.1, upstream plasma beta is 0.3, the shock angle is 70 degrees. The ion to electron mass ratio is 625, the ratio of electron plasma to cyclotron frequency is 10.

Kinetic energies of non-thermal electrons, averaged several gyrations, were divided into those of the guiding center motions parallel and perpendicular to the ambient field and that of the rotations of the guiding center. We then found the following electron acceleration process. Incoming electron is trapped in a thin structure of the time-varying, compressed overshoot magnetic field during a shock reformation process. Simultaneously, it gains a kinetic energy perpendicular to the magnetic field via betatron acceleration, followed by an additional energy increase along the field. The energy conversion from the perpendicular to parallel directions occurs due to a rapid decrease of the overshoot magnetic field; eventually, it is released upstream as a field-aligned beam. The result will be related to in-situ observations of the Earth’s bow shock.

Speaker: Fumiko Otsuka (Kyushu Univ.)
• 15
Statistical Survey of Reservoir Phenomenon in Energetic Proton Events Observed by Multiple Spacecraft

In this work, reservoir phenomenon in the decay phase of gradual solar energetic particle (SEP) events are investigated with two Helios and IMP 8 spacecraft from January 1976 to March 1980, and with two STEREO and SOHO spacecraft from January 2010 to September 2014. Using these data, sixty-two reservoir events of solar energetic protons were identified, and the effects of perpendicular diffusion and magnetic mirror on the formation of the reservoir phenomenon have been studied. We find that the reservoir events could be observed in almost all longitudes in the ecliptic at 1 AU, and thus the perpendicular diffusion in the interplanetary space is an important mechanism to explain the uniform distribution of SEPs. Furthermore, in the 1976 April 30 event, the effects of magnetic mirror associated with an interplanetary coronal mass ejection (ICME) were observed during the reservoir phenomenon. Therefore, the effects of magnetic mirror could also help to form the reservoir phenomenon. This study could improve the understanding of the propagation of SEPs in the interplanetary space.

Speaker: Yang Wang
• 16
Parker Solar Probe’s Measurements of the November 29, 2020 Large Solar Energetic Particle Event

On November 29, 2020 active region 12790 was located just beyond the east limb of the Sun as viewed by Earth. It erupted at 12:34UT with an M4.4 flare (as measured by GOES) and launched a coronal mass ejection (CME) traveling ~1700 km/s. Not surprisingly, this fast CME drove a shock that accelerated particles up to tens of MeV/nuc. More unusual was that these solar energetic particles (SEPs) quickly filled the inner heliosphere and the event was observed by spacecraft distributed around the Sun, including Parker Solar Probe (PSP), STEREO-A, Solar Orbiter, and those near Earth such as ACE and SOHO. This was the first large SEP event detected by the Integrated Science Investigation of the Sun (ISʘIS) suite on PSP and its first opportunity to make measurements of heavy ion spectra up to tens of MeV/nuc. Here we present an overview of event characteristics as determined by ISʘIS, including H, He, O, and Fe spectra, composition as a function of energy, and temporal variations of the energetic particle intensities throughout the event.

Speaker: Christina Cohen (Caltech)
• 17
Time Evolution of Parallel Shock Accelerated Particle Spectrum Bend-over Energy

Shock acceleration is an important mechanism to accelerate energetic particles. Using test-particle simulations we investigate the time evolution of the accelerated particle energy spectrum in the downstream of a parallel shock with magnetic turbulence. From simulation results we obtain power-law energy spectra with a bend-over energy. It is shown that the bend-over energy increases with time. With the particle mean acceleration time and mean momentum change during each cycle of the shock crossing from the diffusive shock acceleration model, a time-dependent differential equation for the maximum energy of particles accelerated at the shock can be approximately obtained, we assume the model can be used to describe the time evolution of the bend-over energy. It is found that the bend-over energy from simulations agrees well with the theoretical model with the nonlinear diffusion theory.

Speaker: Gang Qin
• 18
Observations and numerical simulations of impulsive SEP events with Ulysses and ACE observations

We study the latitudinal extent of the impulsive solar energetic particle (SEP) events of 2000 June 10 and 2001 December 26 using energetic electron observations from the ACE and Ulysses. We investigate the effects of particle source and transport on the profiles. We get the best fit parameters for simulations by comparing simulations with the two spacecraft observations. We show that perpendicular diffusion and adiabatic cooling can significantly affect the propagation of particles. In addition, it is found that the start and peak times of particle injections are between the onset and peak times of flare for the two events. Furthermore, we have theoretical models for the peak intensity of the particle source and the time interval from the onset of flares to the peak time of the particle source. We show that the theories agree well with the best fit parameters.

Speaker: L.-L. Lian
• 19
Energy Balance at Interplanetary Shocks: In-situ Measurement of the Fraction in Supra-thermal and Energetic Ions with ACE and Wind

Energetic particles generated by interplanetary shocks can drain a non-negligible fraction of the upstream ram pressure. We have selected a sample of shocks observed in-situ at 1 AU by the ACE and Wind spacecraft from the CfA Interplanetary Shock Database, which provides high-resolution data on solar wind plasma, shock parameters, and the local magnetic field. Time-series of the non-Maxwellian (supra-thermal and higher-energy) particle energy spectra were acquired for each event, averaged for one hour before and after the shock time, and integrated over velocity space to ascertain their partial pressure. Using the Rankine-Hugoniot MHD jump conditions, we find that the fraction of the total upstream energy flux density transferred to non-Maxwellian particles can reach about 15-35%. Notably, our sample shows that neither the Alfven Mach number nor the angle between the shock normal and upstream magnetic field are correlated with the energy drained by the particles. The findings are also insensitive to the offset of the time interval used for the partial pressure estimate. We obtain similar results, although with larger error bars, using shock parameters from the IPShocks database.

Speaker: Liam David (Student, University of Arizona)
• 20
Imbalance acceleration/escape of energetic particles at interplanetary shocks: effect on spectral steepening

Growing multispacecraft networks are broadening the opportunity of measuring energy spectra of energetic particles at interplanetary shocks over three decades or more in energy at the same distance (different from 1 AU) from the Sun. Energetic particles spectra at interplanetary shocks often exhibit a non-power law shape, even within two energy decades. We have introduced a 1D transport equation accounting for particle acceleration and escape, both allowed at all particle energies. The diffusion is contributed by self-generated turbulence close to the shock and by pre-existing turbulence far upstream. The upstream particle intensity profile steepens within one diffusion length from the shock as compared with diffusive shock acceleration rollover. The spectrum, controlled by macroscopic parameters such as shock compression, speed, far upstream diffusion coefficient and escape time at the shock, can be reduced to a log-parabola, that has been shown to describe the escape in a probabilistic approach. In the case of upstream uniform diffusion coefficient, the customarily used power law/exponential cut off solution is retrieved.

Speaker: Federico Fraschetti (CfA | Harvard & Smithsonian / University of Arizona)
• Discussion: 25 Blazars, AGN | MM 06

#### 06

• 21
A Two-zone Blazar Radiation Model for “Orphan” Neutrino Flares

In this work, we investigate the 2014–2015 neutrino flare associated with the blazar TXS 0506+056 and a recently discovered muon neutrino event IceCube-200107A in spatial coincidence with the blazar 4FGL J0955.1+3551, under the framework of a two-zone radiation model of blazars where an inner/outer blob close to/far from the supermassive black hole is invoked. An interesting feature that the two sources have in common is that no evidence of GeV gamma-ray activity is found during the neutrino detection period, probably implying a large opacity for GeV gamma rays in the neutrino production region. In our model, continuous particle acceleration/injection takes place in the inner blob at the jet base, where the hot X-ray corona of the supermassive black hole provides target photon fields for efficient neutrino production and strong GeV gamma-ray absorption. We show that this model can self-consistently interpret the neutrino emission from both blazars in a large parameter space. In the meantime, the dissipation processes in outer blob are responsible for the simultaneous multiwavelength emission of both sources. In agreement with previous studies of TXS 0506+056, an intense MeV emission from the induced electromagnetic cascade in the inner blob is robustly expected to accompany the neutrino flare in our model and could be used to test the model using the next-generation MeV gamma-ray detector in the future.

Speaker: Rui Xue (Zhejiang Normal University)
• 22
Extrapolating FR-0 radio galaxy source properties from the propagation of multi-messenger ultra-high-energy cosmic rays

Recently, it has been shown that relatively low luminosity Fanaroff-Riley type 0 (FR-0) radio galaxies are a good candidate source class for a predominant fraction of cosmic rays (CR) accelerated to ultra-high energies (UHE, E>10^18 eV). FR-0s can potentially provide a significant fraction of the UHECR energy density as they are much more numerous in the local universe (up to a factor of ~5 with z<= 0.05) than more energetic radio galaxies such as FR-1s or FR-2s.

In the present work, UHECR mass composition and energy spectra at the FR-0 sources are estimated by fitting simulation results to the published Pierre Auger Observatory and Telescope Array data. This fitting is done using a simulated isotropic sky distribution extrapolated from the measured FR-0 galaxy properties and propagating CRs in plausible extragalactic magnetic field configurations using the CRPropa3 framework. In addition, we present estimates of the fluxes of secondary photons and neutrinos created in UHECR interactions with cosmic photon backgrounds during CR propagation. With this approach, we aim to investigate the properties of the sources with the help of observational multi-messenger data.

Speaker: Jon Paul Lundquist (University of Nova Gorica)
• 23
High-Energy Neutrinos from NGC 1068

IceCube has observed an excess of neutrino events over expectations from the isotropic background from the direction of NGC 1068. The excess is inconsistent with background expectations at the level of 2.9σ after accounting for statitsical trials. Even though the excess is not statistical significant yet, it is interesting to entertain the possibility that it corresponds to a real signal. Assuming a single power-law spectrum, the IceCube Collaboration has reported a best-fit flux ∼ 3 × 10^{−11} (E/TeV)^{−3.2} (TeV cm^2 s)^{−1} , where E is the neutrino energy. Taking account of new physics and astronomy developments we give a revised high-energy neutrino flux for the Stecker-Done-Salamon-Sommers AGN core model and show that it can accommodate IceCube observations.

Speaker: Luis Anchordoqui (Lehman College, City University of New York)
• 24
Testing the AGN Radio and Neutrino correlation using the MOJAVE catalog and 10 years of IceCube Data

On 22 September 2017 IceCube reported a high-energy neutrino event which was found to be coincident with a flaring blazar, TXS 0506+056. This first multi-messenger observation hinted at blazars being sources of observed high-energy astrophysical neutrinos and raised a need for extensive correlation studies. Recent work shows that the internal absorption of gamma rays, and their interactions intrinsic to the source and with the extragalactic background, will cause a lack of energetic gamma-ray and neutrino correlation while hinting towards a correlation between neutrinos and lower photon energy observations in the X-ray and radio bands. Studies based on published IceCube alerts and radio observations, report a possible radio-neutrino correlation in both gamma-ray bright and gamma-ray dim active galactic nuclei (AGN). However, they have marginal statistical significance due to limited available data. We present a correlation analysis between 15 GHz radio observations of AGN reported in the MOJAVE XV catalog and 10 years of IceCube detector data and discuss the results derived from a time averaged stacking analysis.

Speaker: Abhishek Desai (University of Wisconsin Madison)
• 25
Fermi-LAT realtime follow-ups of high-energy neutrino alerts

The detection of the flaring gamma-ray blazar TXS 0506+056 in spatial and temporal coincidence with the high-energy neutrino IC-170922A represents a milestone for multi-messenger astronomy. The prompt multi-wavelength coverage from several ground- and space-based facilities of this special event was enabled thanks to the key role of the Fermi-Large Area Telescope (LAT), continuously monitoring the gamma-ray sky. Exceptional variable and transient events, such as bright gamma-ray flares of blazars, are regularly reported to the whole astronomical community to enable prompt multi-wavelength observations of the astrophysical sources. As soon as real-time IceCube high-energy neutrino event alerts are received, the relevant positions are searched, at multiple timescales, for gamma-ray activity from known sources and newly detected emitters positionally consistent with the neutrino localization.
In this contribution, we present an overview of follow-up activities and strategies for the real-time neutrino alerts with the Fermi-LAT, focusing on some interesting observed coincidences with gamma-ray sources. We will also discuss future plans and improvements in the strategies for the identification of gamma-ray counterparts of single high-energy neutrinos.

Speaker: Simone Garrappa (DESY Zeuthen)
• 26

The Astrophysical Multimessenger Observatory Network (AMON), has developed a real-time multi-messenger alert program. The system performs coincidence analyses of datasets from gamma-ray and neutrino detectors, making the Neutrino-Electromagnetic (NuEM) alert channel. For these analyses, AMON takes advantage of sub-threshold events, i.e., events that by themselves are not significant in the individual detectors. The main purpose of this channel is to search for gamma-ray counterparts of neutrino events. We will describe the different analyses that make-up this channel and present a selection of recent results.

Speaker: Dr Hugo Ayala (Pennsylvania State University)
• 27
Searching for VHE gamma-ray emission associated with IceCube neutrino alerts using FACT, H.E.S.S., MAGIC, and VERITAS

The real-time follow-up of high energy events from neutrino observatories is a promising approach to identify their astrophysical origin. So far, it has provided compelling evidence for a neutrino counterpart: the flaring gamma-ray blazar TXS 0506+056 observed in coincidence with the high-energy neutrino IC170922A detected by IceCube. The detection of very-high-energy (VHE, E > 100 GeV) gamma rays from this source supported the association and constrained the modeling of the blazar emission at the time of the IceCube event. The four imaging atmospheric Cherenkov telescope experiments (IACTs) - FACT, H.E.S.S., MAGIC, and VERITAS - operate an active follow-up program of target-of-opportunity observations of neutrino alerts sent by IceCube. This program has two main components: the follow-up of single high-energy neutrino candidate events of potential astrophysical origin, such as IC170922A, and the observation of known gamma-ray sources around which IceCube has identified a cluster of candidate neutrino events. IceCube recently upgraded this second gamma-ray follow-up (GFU) component in collaboration with the IACT groups. We present results from the IACT follow-up program of IceCube neutrino alerts and a description of the upgraded GFU system.

Speaker: Konstancja Satalecka (Z_MAGIC (Experiment MAGIC))
• 28
Electromagnetic and Neutrino Output from Magnetic Reconnection in Poynting Flux Dominated Jets.

Neutrino-emitting blazars may accelerate cosmic ray (CR) protons at the inner regions of the jet, where most of the magnetic energy is likely to be dissipated. In this picture, the spectrum of neutrinos and gamma-rays that leave the source is shaped by the soft photon fields that the parent hadrons encounter before leaving the source. We build a lepto-hadronic emission model based on particle acceleration by magnetic reconnection. The emission is powered by magnetic dissipation in the jet, in the transition from magnetically to kinetically dominated flow. We employ the striped jet model to obtain the jet properties at three characteristic emission regions and derive the associated electromagnetic and neutrino output. We also perform Monte Carlo simulations of the propagation CR protons as an alternative method for calculating the neutrino flux. We apply this emission model to interpret the 2017 multi-messenger event from the blazar TXS0506+056 and we also discuss applications of the model in the context of flat-spectrum radio quasars and BL Lac objects.

Speaker: Dr Juan Carlos Rodríguez-Ramírez (Instituto de Astronomia, Geofisica, e Ciencias Atmosfericas - Universidade de Sao Paulo)
• 29
High-energy neutrinos and gamma-rays from the AGN-driven wind in NGC 1068

Various observations are revealing the widespread occurrence of fast and powerful winds in active galactic nuclei (AGN) that are distinct from relativistic jets, likely launched from accretion disks. Such winds can harbor collisionless shocks at different locations that may induce acceleration of protons and electrons and consequent nonthermal emission. We focus on the inner regions of the winds, where interactions of accelerated protons with the nuclear radiation field and/or ambient gas can induce emission of high-energy neutrinos and gamma-rays. In particular, we address the case of NGC 1068, a nearby Seyfert galaxy bearing a powerful wind, which is a known source of GeV gamma rays as well as a tentative source of sub-PeV neutrinos. Tests and further implications of this scenario are discussed.

Speaker: Susumu Inoue (Bunkyo Univ. / RIKEN)
• 30
Multi-wavelength and neutrino emission from blazar PKS 1502+106

In July of 2019, the IceCube experiment detected a high-energy neutrino from the direction of the powerful quasar PKS 1502+106. I discuss the results of multi-wavelength and multi-messenger modeling of this source, using a fully self-consistent one-zone model that includes the contribution of radiation fields external to the jet. Three distinct activity states of the blazar can be identified: one quiescent state and two flaring states with hard and soft gamma-ray spectra. All three states ca be described by the same leptohadronic model, which also predicts a substantial neutrino flux. These results are compatible with the detection of a neutrino during the quiescent state, based on event rate statistics. The soft X-ray spectra observed during bright flares strongly suggest a hadronic contribution, which can be interpreted as additional evidence for cosmic ray acceleration in the source independently of neutrino observations.

Speaker: Xavier Rodrigues (DESY / Ruhr University Bochum)
• 31
Probing Neutrino Emission from X-ray Blazar Flares observed with Swift-XRT

Blazars are a subclass of active galaxies with jets closely aligned to the observer's line of sight. In addition, they are the most powerful persistent sources across the electromagnetic spectrum in the universe. The detection of a high-energy neutrino from the flaring blazar TXS 0506+056 and the subsequent discovery of a neutrino excess from the same direction have naturally strengthened the hypothesis that blazars are cosmic neutrino sources. The lack, however, of gamma-ray flaring activity during the latter period challenges the standard scenario of correlated gamma-ray and high-energy neutrino emission in blazars. Motivated by a novel theoretical scenario where neutrinos are produced by energetic protons interacting with their own X-ray synchrotron photons, we make neutrino predictions for X-ray flaring blazars. Our sample consists of all blazars observed with the X-ray Telescope (XRT) on board Swift more than 50 times from November 2004 to November 2020. To statistically identify an X-ray flaring state we apply the Bayesian Block algorithm to the 1 keV XRT light curves of frequently observed blazars. Using X-ray spectral information during the flaring states, we compute for each flare the 1-10 keV energy fluence, which is a good proxy for the all-flavor neutrino fluence in the adopted theoretical scenario. We present the expected number of muon neutrino events with IceCube for each source as well as the stacked signal from all X-ray flares of the selected sample. We discuss the implications of our results for IceCube and IceCube Gen-2.

Speaker: Mr Stamatios Ilias Stathopoulos (National and Kapodistrian University of Athens)
• 32
Radio astronomy locates the neutrino origin in bright blazars

High-energy astrophysical neutrinos have been observed by multiple telescopes in the last decade, but their sources still remained unknown. We address the problem of locating astrophysical neutrinos’ sources in a statistical manner. We show that blazars positionally associated with IceCube neutrino detections have stronger parsec-scale radio cores than the rest of the sample. The probability of a chance coincidence is only 4×10^-5 corresponding to a significance of 4.1σ. We explicitly list five strong radio blazars as highly probable sources of neutrinos above 200 TeV: 3C 279, NRAO 530, TXS 1308+326, PKS 1741-038, and PKS 2145+067. Turns out that there are at least 70 more radio-bright blazars that emit neutrinos of lower energies starting from TeVs. Moreover, we utilize continuous RATAN-600 monitoring of VLBI-selected blazars to find that radio flares at frequencies above 10 GHz coincide with neutrino arrival dates. The most pronounced example of such behavior is PKS 1502+106 that experienced a major flare in 2019. We conclude that the entire IceCube astrophysical neutrino flux derived from muon-track analyses may be explained by blazars, that is AGNs with bright Doppler-boosted jets. High-energy neutrinos can be produced in photohadronic interactions within parsec-scale relativistic jets. Radio-bright blazars associated with neutrino detections have very diverse gamma-ray properties, which suggests that gamma-rays and neutrinos may be produced in different regions of blazars and not directly related. A narrow jet viewing angle is, however, required to detect either of them.

Speaker: Alexander Plavin (Astro Space Center of Lebedev Physical Institute)
• 33
TELAMON: Monitoring of AGN with the Effelsberg 100-m Telescope in the Context of Astroparticle Physics

We introduce the TELAMON program, which is using the Effelsberg 100-m telescope to monitor the radio spectra of active galactic nuclei (AGN) under scrutiny in astroparticle physics, namely TeV blazars and neutrino-associated AGN. Thanks to its large dish aperture and sensitive instrumentation, the Effelsberg telescope can yield superior radio data over other programs in the low flux-density regime down to several 10mJy. This is a particular strength in the case of TeV-emitting blazars, which are often comparatively faint radio sources of the high-synchrotron peaked type. We perform high-cadence high-frequency observations every 2-4 weeks at multiple frequencies up to 44GHz. This setup is well suited to trace dynamical processes in the compact parsec-scale jets of blazars related to high-energy flares or neutrino detections. Our sample currently covers about 40 sources and puts its focus on the high-peaked BL Lac objects and extreme blazars most frequently observed by TeV telescopes. Here, we introduce the TELAMON program characteristics and present first results obtained since fall 2020.

• 34
Testing high energy neutrino emission from the Fermi Gamma-ray Space Telescope Large Area Telescope (4LAC) sources.

The detection of the high-energy neutrino IC-170822A in spatial (within the error region) and temporal flare activity correlation with the blazar TXS 0506+056 allowed these objects to be considered as progenitor sources of neutrinos. Besides this, no more detection of this kind was reported. Some other neutrinos detected by IceCube show a spatial correlation (within the error region) from other Fermi-LAT detected sources. However, these objects did not show a flare activity like TXS 0506+056. Assuming a lepto-hadronic scenario through pɣ interactions, this work describes the SED in some objects from the fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Gamma-ray Space Telescope Large Area Telescope (4LAC) sources, which are in spatial correlation with neutrinos detected by IceCube. Additionally, we estimate the corresponding neutrino flux counterpart from these sources.

Speaker: Mr Antonio Galván (Institute of Astronomy, UNAM.)
• 35
The Neutrino Contribution of Gamma-Ray Flares from Fermi Bright Blazars

High-energy neutrinos are expected to be produced during gamma-ray flares of blazars through the interaction of high-energy cosmic rays in the jet with photons. As a matter of fact, a high-energy neutrino event, IC-170922A, was detected at the time of a gamma-ray flare from blazar TXS 0506+056 at the level of 3 sigma significance. In this work, we present a statistical study of blazar gamma-ray  flares aiming to constrain their contribution to the blazar neutrino output. We selected 145 gamma-ray bright blazars listed in the Fermi Large Area Telescope (LAT) monitored list and constructed their weekly binned light curves. Using a Bayesian Blocks algorithm to the light curves, we determined the fraction of time spent in the flaring state (flare duty cycle) and the fraction of energy released during each flare. Furthermore, we estimated the neutrino energy flux of each gamma-ray flare by using the general scaling relation $L_\nu \propto (L_\gamma)^\gamma$, $\gamma=1.5-2$, normalized to the quiescent X-ray flux of each blazar. Comparison of the estimated neutrino energy flux with the declination-dependent IceCube sensitivity enables us to constrain the standard neutrino emission models of gamma-ray flares. We also provide the upper-limit contribution of flares of gamma-ray bright blazars to the isotropic diffuse neutrino flux.

Speaker: Kenji Yoshida (Shibaura Institute of Technology)
• Discussion: 31 Fundamental Physics with Neutrinos | NU 05

#### 05

• 36
HE Neutrinos beyond Standard Model: steriles and secret interactions

Ultra High Energy cosmogenic neutrinos may represent a unique opportunity
to unveil possible new physics interactions in the neutrino sector. At
this regard, we have investigated the effects on high and ultrahigh energy
active neutrino fluxes due to active-sterile secret interactions mediated
by a new pseudoscalar particle. These interactions become relevant at
very different energy scales depending on the masses of the scalar
mediator and of sterile neutrino. As a consequence, we have found
interesting phenomenological implications on two benchmark fluxes we
consider, namely an astrophysical power law flux, in the range below 100
PeV, and a cosmogenic flux, in the Ultrahigh energy range.

Speaker: Dr Ninetta Saviano (INFN)
• 37
Measuring neutrino cross-section with IceCube at intermediate energies (~100 GeV to a few TeV)

Whether studying neutrinos for their own sake or as a messenger particle, neutrino cross-sections are critically important for numerous analyses. On the low energy side, measurements from accelerator experiments reach up to a few 100s of GeV. On the high energy side, neutrino-earth absorption measurements extend down to a few TeV. The intermediate energy range has yet to be measured experimentally. This work is made possible by the linear relationship between the event rate and cross-section, and will utilize IceCube muon neutrino data collected between 2010 and 2018. An advanced energy reconstruction, tailored to the unique properties of the energy range and using the full description of photon propagation in ice, is applied to an event sample of neutrino-induced through-going muons to perform a forward folding analysis.

Speaker: Sarah Nowicki (Michigan State University)
• 38
Measuring the Neutrino Cross Section Using 8 years of Upgoing Muon Neutrinos

The IceCube neutrino observatory detects neutrinos at energies orders of magnitude higher than those accessible to current neutrino accelerators. Above 40 TeV, neutrinos traveling through the Earth will be absorbed as they interact via charge current interactions with nuclei, creating a deficit of Earth-crossing neutrinos detected at IceCube. In this analysis we use the Earth as a target to measure the neutrino cross section for muon neutrinos passing through IceCube. The previous published results of this analysis showed the cross section to be consistent with Standard Model predictions for 1 year of IceCube data. In this analysis we extend the studies to 8 years of data, increasing the statistics by an order of magnitude and improving the treatment of systematic uncertainties. We present the updated cross section measurement studies in three decade-wide bins, and compare to previous IceCube cross section results.

Speaker: Sally Robertson (Lawrence Berkeley National Lab)
• 39
Reaching the EeV frontier in neutrino-nucleon cross sections in upcoming neutrino telescopes

Measuring neutrino interactions with matter is arduous but rewarding. To date, experiments have measured the neutrino-nucleon cross section in the MeV-PeV range, using terrestrial and astrophysical neutrinos. We endeavor to push that measurement to the EeV scale, in order to test competing expectations of the deep structure of nucleons and possibly reveal new neutrino interactions. Cosmogenic neutrinos, long-sought but still undiscovered, provide the only feasible way forward. However, because their flux is low, they have evaded detection so far. Fortunately, upcoming in-ice radio-detection neutrino telescopes, like RNO-G and the radio component of IceCube-Gen2, have a real chance of discovering them in the next 10-20 years. In preparation, we perform the first detailed study of their sensitivity to the deep-inelastic-scattering neutrino-nucleon cross section at EeV energies, extracted from the attenuation of the cosmogenic neutrino flux as it traverses the Earth across different directions. We use up-to-date predictions and tools at every step: in the flux of cosmogenic neutrinos---predicted using recent ultra-high-energy cosmic-ray measurements---in their propagation inside the Earth---computed using leading and sub-leading neutrino interactions---and in their detection in radio-based neutrino telescopes---based on advanced simulated detector responses.

Speaker: Victor Valera (Niels Bohr Institute)
• 40
Rigorous predictions for prompt neutrino fluxes in view of VLVnT upgrades

The existence of a flux of prompt atmospheric neutrinos from the decay of heavy hadrons resulting from the interaction of cosmic rays with the atmospheric nuclei is predicted by theory. Very Large Volume Neutrino Telescopes, like Icecube, KM3NeT and Baikal-GVD, should be sensitive to this neutrino component, that represents a background for the neutrinos from far astrophysical sources. However, no clear experimental evidence of prompt neutrino fluxes has been found, at least so far. In particular, the prompt neutrino component well fits to zero even in the most recent analysis of High Energy Starting Events by the IceCube collaboration, published last autumn. On the other hand, the analysis of through-going muon tracks, more sensitive to prompt neutrinos than the previous one, has established an upper limit on prompt neutrino fluxes.
Our collaboration has been active in providing accurate predictions for prompt neutrino fluxes in the last few years, on the basis of rigorous QCD calculations, and in assessing many of the uncertainties related to these predictions. We discuss our most recent results and their uncertainties, which we believe constitute the most accurate and comprehensive prediction of prompt neutrino fluxes available at present, and show how they challenge the present experimental limits. We are confident that, increasing the experimental capabilities and statistical sample, as possible through e.g. the IceCube-Gen2 upgrade, will help in sharing further light on the prompt neutrino issues.

Speaker: Maria Vittoria Garzelli (UNI/TH (Uni Hamburg, Institut fuer Theoretische Physik))
• 41
Studying neutrinos at the LHC-FASER ~ its impact to the cosmic-ray physics

Studies of high energy proton interactions have been basic inputs to understand the cosmic-ray spectra observed on the earth. Yet, the experimental knowledge with controlled beams has been limited. In fact, uncertainties of the forward hadron production are very large due to the lack of experimental data. The FASER experiment is proposed to measure particles, such as neutrinos and hypothetical dark-sector particles, at the forward location of the 14 TeV proton-proton collisions at the LHC. As it corresponds to 100-PeV proton interactions in fixed target mode, a precise measurement by FASER would provide information relevant for PeV-scale cosmic rays. By studying three flavor neutrinos with the dedicated neutrino detector (FASERnu), FASER will lead to a quantitative understanding of prompt neutrinos, which is an important background towards the astrophysical neutrino observation by neutrino telescopes such as IceCube. In particular, the electron and tau neutrinos have strong links with charmed hadron production. And, the FASER measurements may also shed light on the unresolved muon excess at the high energy. FASER is going to start taking data in 2022. We expect about 8000 numu, 1300 nue and 20 nutau CC interactions at the TeV energy scale during Run 3 of the LHC operation (2022-2024) with a 1.1 tons emulsion-based neutrino detector. We report here the overview and prospect of the FASER experiment in relation to the cosmic-ray physics, together with the first LHC neutrino candidates that we caught in the pilot run held in 2018.

Speaker: Akitaka Ariga (Chiba University)
• 42
The Future of High-Energy Astrophysical Neutrino Flavor Measurements

The next generation of neutrino telescopes, including Baikal-GVD, KM3NeT, P-ONE, TAMBO, and IceCube-Gen2, will be able to determine the flavor of high-energy astrophysical neutrinos with 10% uncertainties. With the aid of future neutrino oscillation experiments --- in particular JUNO, DUNE, and Hyper-Kamiokande --- the regions of flavor composition at Earth that are allowed by neutrino oscillations will shrink by a factor of ten between 2020 and 2040. We critically examine the ability of future experiments and show how these improvements will help us pin down the source of high-energy astrophysical neutrinos and a sub-dominant neutrino production mechanism with and without unitarity assumed. As an illustration of beyond-the-Standard-Model physics, we also show that the future neutrino measurements will constrain the decay rate of heavy neutrinos to be below $2\times 10^{-5}~$$m$/eV/s assuming they decay into invisible particles.

Speaker: Ningqiang Song (Queen's University and Perimeter Institute)
• 43
IceCube constraints on Violation of Equivalence Principle

Among the information provided by high energy neutrinos, a promising possibility is to analyze the effects of a Violation of Equivalence Principle (VEP) on neutrino oscillations. We analyze the IceCube data on atmospheric neutrino fluxes under the assumption of a VEP and obtain updated constraints on the parameter space with the benchmark choice that neutrinos with different masses couple with different strengths to the gravitational field. In this case we find that the VEP parameters times the local gravitational potential at Earth can be constrained at the level of $10^{-27}$. We show that the constraints from atmospheric neutrinos strongly depend on the assumption that the neutrino eigenstates interacting diagonally with the gravitational field coincide with the mass eigenstates, which is not a priori justified: this is particularly clear in the case that the basis of diagonal gravitational interaction coincide with the flavor basis, which cannot be constrained by the observation of atmospheric neutrinos. Finally, we quantitatively study the effect of a VEP on the flavor composition of the astrophysical neutrinos, stressing again the interplay with the basis in which the VEP is diagonal: we find that for some choices of such basis the flavor ratio measured by IceCube can significantly change.

Speaker: Damiano Francesco Giuseppe Fiorillo (University of Naples "Federico II")
• 44
Scalar Non Standard Interactions at long baseline experiments

The discovery of neutrino oscillation confirms neutrinos have mass and the Standard Model(SM) of particle physics is not complete. It needs an extension in order to accommodate the masses and mixing of neutrinos, which essentially leads to beyond SM(BSM) physics. The unknown couplings involving neutrinos, so-called the Non-Standard Interactions(NSIs)[1] may appear as a ’new physics’ in different neutrino experiments. Neutrino NSI can have a sizable impact on neutrino oscillation and can impact the measurements of different mixing parameters in various neutrino experiments. The recent work on scalar NSI[2] has shown a great potential to probe it further. Unlike vector NSI, scalar NSI appears as a correction to the neutrino mass matrix rather than acting as a matter potential. This may lead to a significantly different phenomenological consequence in different neutrino experiments. Moreover, as scalar NSI affects the mass matrix, it also gives a possibility of probing it to different neutrino mass models.
In this work, we explored the effect of scalar NSI in different long-baseline experiments (DUNE, T2HK, etc). We point out that scalar NSI can considerably affect the neutrino oscillation in Long baseline(LBL) experiments and can complicate the measurement of the CP phase. Also as it appears as a correction to the neutrino mass matrix its effect is energy independent, unlike the vector NSI. We also studied the sensitivity of different LBL experiments towards finding the effects of scalar NSI. Also, we put up the possibility of probing it further to various neutrino mass models.

References:

[1] O.G.Miranda and H.Nunokawa, New Journal of Physics, 2015, 17, 095002.

[2] S.F. Ge and S.J. Parke, Phys. Rev. Lett., 2019, 122, 211801.

Speaker: Abinash Medhi (Tezpur University, Assam, India)
• 45
Search for Magnetic Monopoles with ten years of ANTARES data

The present study is an updated search for magnetic monopoles using data taken with the ANTARES neutrino telescope over a period of 10 years (January 2008 to December 2017). In accordance with some grand unification theories, magnetic monopoles could have been created during the phase of symmetry breaking in the early Universe, and accelerated by galactic magnetic fields. As a consequence of their high energy, they could cross the Earth and emit a significant signal in a Cherenkov-based telescope like ANTARES, for appropriate mass and velocity ranges. This analysis uses a run-by-run simulation strategy, as well as a new simulation of magnetic monopoles taking into account the Kasama, Yang and Goldhaber cross section. The results obtained for relativistic magnetic monopoles with velocity v ≥ 0.57c will be presented.

• 46
Search for nuclearites with the KM3NeT detector

Strange quark matter (SQM) is a hypothetical type of matter composed of almost equal quantities of up, down and strange quarks. Massive SQM particles are called nuclearites. Nuclearites with masses greater than $10^{13}$ GeV and velocities of about 250 km/s (typical galactic velocities) could reach the Earth and interact with atoms and molecules of sea water within the sensitive volume of the deep-sea neutrino telescopes. The SQM particles can be detected with the KM3NeT telescope (whose first lines are already installed in the Mediterranean Sea and taking data) through the visible blackbody radiation generated along their path inside or near the instrumented area. In this work the results of a study using Monte Carlo simulations of down-going nuclearites are discussed. Preliminary sensitivities of the KM3NeT experiment for a flux of nuclearites are also presented.

Speaker: Ms Alice Paun (Institute of Space Science (ISS), Atomistilor 409, Magurele, RO-077125 Romania)
• 47
Search for STaus in IceCube

The tau lepton’s supersymmetric partner, the stau, appears in some models as the next-to-lightest particle. This makes it also a long-lived particle. In this scenario, its signature is a long, dim and minimally ionizing track when traveling through the IceCube detector. Independent of their primary energy, the stau tracks appear like low-energy muons in the detector. A potential signal of staus would thus be an excess over muon tracks induced by atmospheric muon neutrinos. Our analysis focuses on the region around the horizon as here the ratio between stau signal and atmospheric background is largest. We will present the sensitivity to constrain the stau mass using IceCube and demonstrate this analysis’s potential with future improvements.

Speaker: Jan-Henrik Schmidt-Dencker
• 48
Sensitivity of the KM3NeT/ORCA detector to the neutrino mass ordering and beyond

The KM3NeT collaboration is currently building a new generation of large-volume water-Cherenkov neutrino telescopes in the Mediterranean sea. Two detectors, ARCA and ORCA, are under construction. They feature different neutrino energy thresholds: TeV range for ARCA and GeV range for ORCA. The main research goal of ORCA is the measurement of the neutrino mass ordering and atmospheric neutrino oscillation parameters, while the detector is also sensitive to a wide variety of other physics topics, including non-standard interactions, sterile neutrinos and Earth tomography, as well as low-energy neutrino astronomy.
This contribution will present an overview of the updated ORCA sensitivity projection to its main science objectives, including - but not limited to - the measurement of the neutrino mass ordering and oscillation parameters Future perspectives for ORCA to serve as far detector for a long baseline neutrino experiment with a neutrino beam from the U70 accelerator complex at Protvino in Russia will also be discussed.

Speaker: Mathieu Perrin-Terrin (Aix Marseille Univ, CNRS/IN2P3, CPPM, Marseille, France)
• 49
Search for exotic neutrino interactions by XMASS-I detector

XMASS is multi-purpose experiment using liquid xenon and is located at the Kamioka Observatory in Japan. The detector consists of a liquid xenon with a single-phase of 832 kg active volume and has a low energy threshold, low backgrounds and large target mass. In XMASS, it is possible to verify the topics of low energy neutrino physics which would give hints on models beyond SM. Now we have searched for exotic neutrino-electron interactions that could be produced by a neutrino millicharge, by a neutrino magnetic moment, or by dark photons using solar neutrinos in XMASS. We analyzed the data between November 2013 and March 2016 for 711days dataset. No significant signals have been observed with predicting the backgrounds in detector. We obtained an upper limit of neutrino millicharge of $5.4\times10^{-11}$e for all flavors of neutrino. We also set individual flavors to be $7.3 \times 10^{-12} e$ for $\nu_e$, $1.1 \times 10^{-11} e$ for $\nu_{\mu}$, and $1.1 \times 10^{-11} e$ for $\nu_{\tau}$. The limits for $\nu_{\mu}$ and $\nu_{\tau}$ are the best direct experimental limits. We also obtain an upper limit for the neutrino magnetic moment of 1.8$\times$10$^{-10}\mu_{B}$. In addition, we obtain upper limits for the coupling constant of dark photons in the $U(1)_{B-L}$ model of 1.3$\times$10$^{-6}$ if the dark photon mass is 1$\times 10^{-3}$ MeV$/c^{2}$, and 8.8$\times$10$^{-5}$ if it is 10 MeV$/c^{2}$. In particular, we almost exclude the possibility to understand the muon $g-2$ anomaly by dark photons.

Speaker: hiroshi ogawa (CST Nihon University, Japan)
• Discussion: 51 The Census of Gamma-Ray Sources | GAD-GAI 04

#### 04

• 50
Exploring the population of Galactic very-high-energy gamma-ray sources

At very high energies (VHE), the emission of gamma rays is dominated by discrete sources. Due to the limited resolution and sensitivity of current-generation instruments, only a small fraction of the total Galactic population of VHE gamma-ray sources has been significantly detected. The larger part of the population can be expected to contribute as a diffuse signal alongside emission originating from propagating cosmic rays. Without quantifying the source population, it is not possible to disentangle these two components. Based on the H.E.S.S. Galactic Plane Scan, a numerical approach has been taken to develop a model of the population of Galactic VHE gamma-ray sources, which is shown to accurately account for the observational bias. We present estimates of the absolute number of sources in the Galactic Plane and their contribution to the total VHE gamma-ray emission for five different spatial source distributions. Prospects for CTA and its ability to constrain the model are discussed. Finally, first results of an extension of our modelling approach using machine learning to extract more information from the available data set are presented.

Speaker: Constantin Steppa (University of Potsdam)
• 51
Galactic Science with the Southern Wide-field Gamma-ray Observatory

The Southern Wide-field Gamma-ray Observatory is a proposed ground-based gamma-ray detector that will be located in the Southern Hemisphere and is currently in its design phase. In this contribution, we will outline the prospects for Galactic science with this Observatory. Particular focus will be given to the detectability of extended sources, such as gamma-ray halos around pulsars; optimisation of the angular resolution to mitigate source confusion between known TeV sources; and studies of the energy resolution and sensitivity required to study the spectral features of PeVatrons at the highest energies. Such a facility will ideally complement contemporaneous observatories in studies of high energy astrophysical processes in our Galaxy.

• 52
Source classification at GeV energies using neura lnetworks with time variability and locations

The Fermi LAT point source catalog contains 10 years of observational data between 50 MeV to 1 TeV. It contains 5064 point sources mostly consisting of BLLs (1131) and FSRQs (694), while pulsars (239) are the most numerous Galactic population. However, a quarter of detected sources remains unclassified and might hide new source classes. The classification is difficult due to bright, diffuse emission from our own galaxy.Recently a machine learning methods were developed for the first time to localize and to classify point sources in the catalog, with performance comparable to that of traditional techniques. Synthetic yearly catalogs are simulated to produce 10 yearly $\gamma$-ray images from 2008 to 2018 in 6 energy bins of the sources. The yearly images provide the network with time variability information of the point sources. The time variable images are fed to the new neural network together with the location in the sky of the point source.
The network then separates the sources into distinct classes. The addition of time dependency and location data should increase the number of classifiable sources compared to the previous network from 3 to 5 (BLLacs, FSRQs, PSRs, PWN+SNR+SPPs, and Fakes), as well as an increase in classification accuracy.

Speaker: Chris van den Oetelaar (Radboud university)
• 53
Survey of the Galactic Plane with the Cherenkov Telescope Array

Observations with the current generation of very-high-energy gamma-ray telescopes have revealed an astonishing variety of particle accelerators in the Milky Way, such as supernova remnants, pulsar wind nebulae, and binary systems. The upcoming Cherenkov Telescope Array (CTA) will be the first instrument to enable a survey of the entire Galactic plane in the energy range from a few tens of GeV to 300 TeV with unprecedented sensitivity and improved angular resolution. In this contribution we will revisit the scientific motivations for the survey, proposed as a Key Science Project for CTA. We will highlight recent progress, including improved physically-motivated models for Galactic source populations and interstellar emission, advance on the optimization of the survey strategy, and the development of pipelines to derive source catalogues tested on simulated data. Based on this, we will provide a new forecast on the properties of the sources that CTA will detect and discuss the expected scientific return from the study of gamma-ray source populations.

Speaker: Quentin Remy
• 54
The First Catalog of Extragalactic Fermi-LAT Transient Sources

The first Fermi Large Area Telescope (LAT) catalog of gamma-ray transient sources (1FLT) comprises sources that were detected on monthly time intervals during the first decade of Fermi-LAT operations. The monthly time scale allows us to identify transient and variable sources that may have not been reported in Fermi-LAT general catalogs.
The analysis was performed for photon energies between 0.1 and 300 GeV using the Pass-8 event-level selection. In the analysis we considered only photons with |b| > 10° to exclude the Galactic plane and therefore to avoid confusion with low-latitude diffuse emission. We have analyzed 120 months and also performed a 15-day shift of each month in order to not lose any flare at the edges of each time bin. The monthly datasets were analyzed using a wavelet-based source detection algorithm that provided the candidate new transient sources. The transient candidates were then analyzed using the standard Fermi-LAT maximum likelihood analysis method. The resulting catalog list has 142 different sources detected with a statistical significance above 4-sigma in at least one monthly bin. About 70% are associated with spectrally soft AGN-type counterparts, principally blazar candidates of uncertain type and flat-spectrum radio quasars, and about 30% of 1FLT sources remain unassociated. This is similar to the fraction of unassociated sources found in the Fermi-LAT general catalogs. The median gamma-ray spectral index of the 1FLT-AGN sources is softer than the median index reported in the latest Fermi-LAT AGN general catalog (4LAC). The sources associated to a 4FGL-DR2 target are not reported in the 1FLT catalog while are reported 6 sources listed also in a previous general catalog (1-3FGL).

Speaker: Dr Isabella Mereu (INFN Perugia)
• 55
The TeV gamma-ray source population of the Milky-Way.

In this work we perform a population study of the H.E.S.S. Galactic Plane Survey (HGPS) catalogue. Namely, we analyze the flux, latitude and longitude distributions of gamma-ray sources detected by H.E.S.S. with the goal of inferring the main properties of galactic TeV source population.
We show that the total Milky Way luminosity in the 1-100 TeV energy range is relatively well constrained by H.E.S.S. data, obtaining $L_{\rm MW} = 1.7^{+0.5}_{-0.4}\times 10^{37} {\rm erg}\,{\rm s}^{-1}$, and that the total Galactic flux in the H.E.S.S. observational window is $\Phi_{\rm tot} = 3.8^{+1.0}_{-1.0}\times 10^{-10} {\rm cm}^{-2}\, {\rm s}^{-1}$.
The above results allows us to estimate the flux produced by sources not resolved by H.E.S.S.. These sources, which are too faint (or too extended) to be detected by H.E.S.S., contribute to the large-scale diffuse signal observed at the TeV range. We show that unresolved source contribution is not negligible (about $60\%$ of the resolved signal measured by H.E.S.S.) and potentially responsible for a large fraction of the diffuse-large scale gamma-ray signal observed by H.E.S.S. and other experiments in the TeV domain.
Finally, in the hypothesis that the majority of bright sources detected by H.E.S.S. are powered by pulsar activity, like e.g. Pulsar Wind Nebulae or TeV halos, we estimate the main properties of the pulsar population: we obtain a constrain on the fading time $\tau$, the initial period $P_{0}$ and the magnetic field $B$.

Speaker: Vittoria Vecchiotti (GSSI)
• 56
Understanding the origin of the extended gamma-ray emission and the physical nature of HESS J1841-055 using observations at TeV energies with the MAGIC telescopes

With the improved sensitivity with respect to the previous generation, current space-borne and ground-based gamma-ray telescopes have made the number of gamma-ray sources detected at GeV-TeV energies increase many folds over the last decade. Many of the detected extended gamma-ray sources are not associated with any known sources at other wavelengths. Understanding the nature of these sources and the origin of the observed high energy gamma-ray emission remains a great challenge. Using the MAGIC telescopes, we have observed one such unassociated gamma-ray source, named HESS J1841-055, at TeV energies. In this talk, we present our detailed investigation on this source using MAGIC data and other multi-waveband information on nearby sources. We discuss the interpretation of this source as a cosmic-ray accelerator.

Speaker: Dr David Green (Max-Planck-Institut for Physics)
• 57
Assessing the signatures imprinted by star-forming galaxies in the cosmic gamma-ray background

In recent years, high-energy gamma-ray emission has been detected from star-forming galaxies in the local universe, including M82, NGC 253, Arp 220 and M33. The bulk of this emission is thought to be of hadronic origin, arising from the interactions of cosmic rays (CRs) with the interstellar medium of their host galaxy. More distant star-forming galaxies would also presumably be bright in gamma-rays, but these would not be resolved as point sources. Instead, they contribute gamma-rays as unresolved sources to the extra-galactic gamma-ray background (EGB). However, despite the wealth of high-quality all-sky EGB data from the Fermi-LAT gamma-ray space telescope collected over more than a decade of operation, the exact contribution of SFGs to the EGB and the signatures their emission would imprint on the gamma-ray sky remains unsettled. In this talk, I will discuss how this can be assessed by modelling the gamma-ray emission from SFG populations above 1 GeV. I will demonstrate that such emission can be characterised by just a small number of key physically-motivated parameters, and outline how source populations would leave anisotropic signatures in the EGB. I will consider model signatures that may be imprinted population classes and discuss how such imprints could yield information about the underlying properties and evolution of SFGs over cosmic time.

Speaker: Ellis Owen (National Tsing Hua University)
• 58
Bridging the Gap - The first sensitive 20-200 MeV catalog

The under-explored MeV band has an extremely rich scientific potential. Awaiting an all-sky MeV mission, it is now the prime time to take full advantage of the capabilities of the Fermi Large Area Telescope to explore this regime. With more than 12 years of the best available dataset (Pass8), we have developed an all-sky analysis to build a sensitive catalog of sources from 20 to 200 MeV. This work will allow us to cover the SED peak of most gamma-ray sources, fundamental to understand their nature, and possibly discover a whole new population of MeV ones. Importantly, this program will start bridging the gap between the MeV and GeV energy bands, strongly supporting the scientific case for a future all-sky MeV mission and enhancing the legacy of the Fermi mission. In this talk I will present the preliminary results of this analysis, highlighting the scientific potential of this project. I will also discuss the difference with respect to the first catalog of low-energy sources (1FLE, Principe et al. 2018).

Speaker: Lea Marcotulli (Clemson University)
• 59
Dissecting the inner Galaxy with gamma-ray pixel count statistics

The nature of the GeV gamma-ray Galactic center excess (GCE) in the data of Fermi-LAT is still under investigation. Different techniques, such as template fitting and photon-count statistical methods, have been applied in the past few years in order to disentangle between a GCE coming from sub-threshold point sources or rather from diffuse emissions, such as the dark matter annihilation in the Galactic halo.
A major limit to all these studies is the modeling of the Galactic diffuse foreground, and the impact of residual mis-modeled emission on the results' robustness.
In Ref.[1], we combine for the first time adaptive template fitting and pixel count statistical methods in order to assess the role of sub-threshold point sources to the GCE, while minimizing the mis-modelling of diffuse emission components.
We reconstruct the flux distribution of point sources in the inner Galaxy well below the Fermi-LAT detection threshold, and measure their radial and longitudinal profiles. We find that point sources and diffuse emission from the Galactic bulge each contributes about 10% of the total emission therein, disclosing a sub-threshold point-source contribution to the GCE.

[1] arXiv:2102.12497

Speaker: Dr Silvia Manconi (Institute for Theoretical Particle Physics and Cosmology, RWTH Aachen)
• 60
Population Studies of Fermi LAT sources

The Fermi Large Area Telescope (LAT) has been detecting hundreds of Galactic sources, most of which are pulsars. Many Galactic sources are still undetected or unresolved due to their low flux, below the Fermi LAT sensitivity, or because of foreground and source confusion. Moreover, among the many unassociated sources, which are one third of the detected sources, a large amount may have Galactic origin.
We present our method of source population synthesis studies for characterizing the general properties of Fermi LAT Galactic gamma-ray sources and for estimating the number of Galactic sources below the Fermi LAT flux sensitivity threshold.
Source density distribution and luminosity function of our Monte-Carlo simulation are constrained by the Galactic sources detected by Fermi LAT. Then, the number of unresolved sources and their contribution to the diffuse emission are estimated by our best model.
This is a long-term project on analyzing the point source catalog and performing theoretical studies of gamma-ray sources. Apart from being interesting on its own, characterizing the general properties of detected sources will also allow to estimate the contribution to the diffuse emission from undetected and unresolved sources. In turn this will help their detection, impacting also other studies of diffuse gamma rays including studies of the interstellar emission and dark matter. Finally, it will also help in the characterization of unassociated sources.

Speaker: Elena Orlando
• 61
The future look at the Galaxy with the Galactic Explorer with a Coded Aperture Mask Compton Telescope (GECCO)

In the past 15 years, observations of the Galaxy at high energies by Fermi-LAT, AGILE, INTEGRAL and very recently by NuSTAR and eROSITA have been shown to be very exciting, allowing discoveries of a variety of objects and unexpected breakthroughs. However, from a few hundreds of KeV to several tens of MeV, the Galaxy remains poorly explored. In this energy range the lack of sufficiently sensitive instruments limits potential discoveries and challenges our understanding of the Galactic high-energy processes and sources.
To solve this issue, GECCO is a new mission concept that will allow high-sensitivity observations of the sky from ~50 KeV to ~10 MeV. It combines a coded aperture mask technique that provides high angular resolution for source detection, and a Compton telescope that provides high-sensitivity measurements of diffuse emissions. Such a combination enables efficient separation between sources and diffuse emissions.
A GECCO-like mission has the potential of answering open questions and leading to new discoveries. Among the most recent challenges regarding the Galaxy, sensitive observations at MeV energies with unprecedented high resolution will open a new window in understanding complicated regions such as the inner Galaxy, the origin of the Fermi Bubbles, the origin of the 511 keV line, and it will provide new insights on element formation in dynamical environments, on possible Galactic winds, and on the mechanisms of propagation of the low-energetic cosmic rays, their sources and their role on the Galaxy evolution.

Speaker: Elena Orlando
• 62
The new release of the fourth Fermi LAT source catalog

The third release of the Fourth Catalog of Fermi-LAT Sources (4FGL-DR3), based on 12 years of data between 50 MeV and 1 TeV, is presented. Improvements in the analysis method relative to the original 4FGL catalog and new features are reviewed. The 4FGL-DR3 includes about 750 more sources than the previous release (4FGL-DR2, obtained with 10 years of data) and about 1500 more sources than 4FGL. About 40% of the new sources are associated with counterparts at other wavelengths, which are mostly blazar candidates. The properties of the global set of unassociated sources reported in the catalog are discussed, with particular attention to those lying close to the Galactic plane. A population of unassociated sources that do not fit in with already known classes of gamma-ray emitters is emphasized.

Speaker: Benoit Lott (CENBG)
• Tuesday, July 13
• Discussion: 02 Constraining UHECR sources | CRI 03

#### 03

• 63
FR-0 jetted active galaxies: extending the zoo of candidate sites for UHECR acceleration

Fanaroff Riley (FR) 0 radio galaxies form a low luminosity extension of the well established ultrahigh energy cosmic ray (UHECR) candidate accelerators FR-1 and FR-2 galaxies. Their much higher number density – up to a factor 5 more numerous compared to FR-1 with $z<= 0.05$ – makes them good candidate sources for an isotropic contribution to the observed UHECR flux. Here, acceleration and survival of UHECR in prevailing conditions of the FR-0 environment are discussed.

First an average spectral energy distribution (SED) is compiled based on the FR0CAT. These photon fields, composed of a jet and a host galaxy component, form a minimal target field for the UHECR, which will suffer from electromagnetic pair production, photo disintegration, photo-meson production losses, and synchrotron radiation. The two most promising acceleration scenarios based on Fermi-I order and gradual shear acceleration are discussed as well as different escape scenarios.

When gradual shear acceleration is preceded by an efficient acceleration mechanism, e.g., Fermi-I or others, FR-0 galaxies are likely UHECR accelerators. This scenario requires a jet Lorentz factor of $\gamma>1.6$ to yield gradual shear acceleration which is faster than the corresponding escape. In less optimistic models a contribution to the cosmic-ray flux between knee and ankle is expected relatively independent of the realized turbulence and acceleration.

Speaker: Lukas Merten (University of Innsbruck)
• 64
UHECR from high- and low-luminosity GRBs

We discuss the production of multiple messengers including UHECR, EM radiation and neutrinos in Gamma-Ray Bursts in models with multiple interaction regions.
We demonstrate that standard high-luminosity bursts can explain the UHECR spectrum as as measured by the Pierre Auger Observatory, and derive the required source injection composition for different engine realisations. We discuss how multi-messenger observations can be used to discriminate between models by explicitly calculating the expected source and cosmogenic neutrino fluxes as well as the photon light curves. In addition, a separate population of LL-GRBs may exist, for which we show that different nuclei can indeed reach UHECR energies. For this purpose, we self-consistently model the radiation fields in prototypes inspired by real GRBs. We connect the maximal energies attainable for cosmic-ray nuclei to a possible VHE and HE component in the SED.

Speaker: Annika Rudolph (Z_THAT (Theoretische Astroteilchenphysik))
• 65
Ultrahigh-energy cosmic-ray interactions as the origin of VHE gamma-rays from BL Lacs

We explain the observed multiwavelength photon spectrum of a number of BL Lac objects detected at very high energy (VHE, $E > 30$ GeV), using a lepto-hadronic emission model. The one-zone leptonic emission is employed to fit the synchrotron peak. Subsequently, the SSC spectrum is calculated, such that it extends up to the highest energy possible for the jet parameters considered. The data points beyond this energy, and also in the entire VHE range are well explained using a hadronic emission model. The ultrahigh-energy cosmic rays (UHECRs, $E> 0.1$ EeV) escaping from the source interact with the extragalactic background light (EBL) during propagation over cosmological distances to initiate electromagnetic cascade down to $\sim1$ GeV energies. The resulting photon spectrum peaks at $\sim1$ TeV energies. We consider a random turbulent extragalactic magnetic field (EGMF) with a Kolmogorov power spectrum to find the survival rate of UHECRs within 0.1 degrees of the direction of propagation in which the observer is situated. We restrict ourselves to an RMS value of EGMF, $B_{\rm rms}\sim 10^{-5}$ nG, for a significant contribution to the photon spectral energy distribution (SED) from UHECR interactions. We found that UHECR interactions on the EBL and secondary cascade emission can fit gamma-ray data from the BL Lacs we considered at the highest energies. The required luminosity in UHECRs and corresponding jet power are below the Eddington luminosities of the super-massive black holes in these BL Lacs.

Speaker: Saikat Das (Raman Research Institute, India)
• 66
Cosmographic model of the astroparticle skies

Modeling the extragalactic astroparticle skies involves reconstructing the 3D distribution of the most extreme sources in the Universe. Full-sky tomographic surveys at near-infrared wavelengths have already enabled the astroparticle community to bind the density of sources of astrophysical neutrinos and ultra-high cosmic rays (UHECRs), constrain the distribution of binary black-hole mergers and identify some of the components of the extragalactic gamma-ray background. This contribution will present the efforts of cleaning and complementing the stellar mass catalogs developed by the gravitational-wave and near-infrared communities, in order to obtain a cosmographic view on stellar mass ($M_*$) and star formation rate (SFR). Unprecedented cosmography is offered by a sample of about 400,000 galaxies within 350 Mpc, with a 50-50 ratio of spectroscopic and photometric distances, $M_*$, SFR and corrections for incompleteness with increasing distance and decreasing Galactic latitude. The inferred 3D distribution of $M_*$ and SFR is consistent with cosmic flows. The $M_*$ and SFR densities converge towards values compatible with deep-field observations beyond 100 Mpc, suggesting a close-to-isotropic distribution of more distant sources. In addition to discussing relevant applications for the four astroparticle communities, this contribution will highlight the distribution of magnetic fields at Mpc scales deduced from the 3D distribution of matter, which is believed to be crucial in shaping the ultra-high-energy sky. These efforts provide a new basis for modeling UHECR anisotropies, which bodes well for the identification of their long-sought sources.

Speaker: Jonathan Biteau (Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France)
• 67
Active galactic nuclei as neutrino sources in the PeV and EeV regimes

Active galactic nuclei (AGNs) are amongst the most promising neutrino source candidates, due to their potential to accelerate cosmic rays in their relativistic jets. The IceCube observatory has already detected several events from the direction of known gamma-ray blazar AGNs, like TXS 0506+056 and, more recently, PKS 1502+106. Through numerical modeling, we can show that neutrino emission is compatible with the available multi-wavelength observations from these sources. By generalizing these models, we can show that the diffuse IceCube flux can, under certain conditions, be fully explained by low-luminosity BL Lacs, while the contribution from bright gamma-ray quasars is severely constrained by the IceCube limits. On the other hand, it is also possible that AGNs accelerate cosmic rays up to ultra-high energies. In that scenario, detailed modeling shows that the AGN population can produce large fluxes EeV neutrinos, while still obeying the current IceCube stacking limits in the PeV regime. I will also argue that the flux of EeV neutrinos produced inside AGN jets can outshine the cosmogenic contribution, which has important implications for the search strategy of future radio neutrino telescopes.

Speaker: Xavier Rodrigues (DESY / Ruhr University Bochum)
• 68
Constraining the origin of UHECRs and astrophysical neutrinos

We constrain properties of ultrahigh energy cosmic ray source environments (and potentially astrophysical neutrino sources), including their photon temperature, gas density, size, magnetic field strength and coherence length, using UHECR and neutrino spectra and composition. Our analysis represents a new type of information on UHECR sources, independent of the mechanism responsible for the UHECR acceleration. We also explore the possibility of a common origin of UHECRs and astrophysical neutrinos and further constrain sources which are consistent with this possibility. We show that the common origin hypothesis can only be satisfied for certain hadronic interaction models, showing that multimessenger analyses have the power to also constrain hadronic physics beyond LHC energies.

Speaker: Marco Muzio (New York University)
• 69
Thermal-to-nonthermal element abundances in different Galactic environments

The nonthermal source abundances of elements play a crucial role in the understanding of cosmic ray phenomena from a few GeV up to several tens of EeV. In this presentation a first systematic approach is shown that describes the change of the abundances from the thermal to the nonthermal state via diffusive shock acceleration by a temporally evolving shock. Hereby, not only time-dependent ionization states of elements contained in the ambient gas are considered, but also elements condensed on solid, charged dust grains which can be injected into the acceleration process as well. This generic parametrized model is then applied to the case of particle acceleration by supernova remnants in various ISM phases as well as Wolf-Rayet wind environments. The resulting predictions for low energy cosmic ray (LECR) source abundances are compared with the data obtained by various experiments revealing the importance of dust grains as well as the possible contribution of different ISM environments to the observed LECR flux.

Speaker: Björn Eichmann (Ruhr-Universität Bochum, Theoretische Physik IV)
• 70
The problematic connection between low-luminosity gamma-ray bursts and ultra-high-energy cosmic rays

Ultra-high-energy cosmic rays (UHECR) are the most energetic particles ever observed. What astrophysical sources are responsible for their immense acceleration remains unknown despite decades of research. In this talk, I will investigate whether low-luminosity gamma-ray bursts (llGRBs), short-lived cosmic explosions currently seen as one of the most promising acceleration candidates, can be the main sources of UHECR. Our study focuses on the radiation from the less energetic electrons, which are inevitably accelerated in the same region. This radiation can be characterized and compared to observations of llGRBs. We find that the radiation from these electrons would be much too luminous, showing that llGRBs would have to be orders of magnitude brighter if they hosted significant UHECR acceleration. This result challenges llGRBs as accelerators of UHECR.

Speaker: Filip Samuelsson (KTH Royal Institute of Technology)
• 71
A combined fit of energy spectrum, shower depth distribution and arrival directions to constrain astrophysical models of UHECR sources

The combined fit of the measured energy spectrum and shower depth distribution of ultra-high-energy cosmic rays is known to constrain the parameters of astrophysical scenarios with homogeneous source distributions. Further measurements show that the cosmic-ray arrival directions agree better with the directions and fluxes of catalogs of starburst galaxies and active galactic nuclei than with isotropy.
Here, we present a novel combination of both analyses. For that, a three-dimensional universe model containing a nearby source population and a homogeneous background source distribution is built, and its parameters are adapted using a combined fit of energy spectrum, shower depth distribution and energy-dependent arrival directions. The model takes into account a symmetric magnetic field blurring, source evolution and interactions during propagation.
We use simulated data, which resemble measurements of the Pierre Auger Observatory, to evaluate the method’s sensitivity. By that, we are able to verify that the source parameters as well as the fraction of events from the nearby source population and the size of the magnetic field blurring are determined correctly, and that the data is described by the fitted model including the catalog sources with their respective fluxes and three-dimensional positions. We demonstrate that by combining all three measurements we reach the sensitivity necessary to discriminate between the catalogs of starburst galaxies and active galactic nuclei.

Speaker: Teresa Bister (RWTH Aachen University)
• 72
Excited isomer photons and the VHE emission from Centaurus A

The very-high-energy (VHE) emission from Centaurus A (Cen A) observed by the H.E.S.S. telescopes cannot be explained by simple synchrotron-self-Compton (SSC) models. Motivated by the reported UHECR hotspot in the direction of Cen A, we investigate a scenario in which excited isomer photons of heavy nuclei can account for these VHE photons.
Our fully self-consistent model includes a leptonic SSC scenario with a hadronic high-energy component from the pc-scale core region which explains the SED below TeV energies. As expected, the core of the jet is optically thick to above TeV gamma-rays that are produced in nuclear disintegrations. However, of a fraction of excited isomers produced in photodisintegration interactions of cosmic-ray nuclei is long-lived enough for the isomers to escape the core region. We consider the isomeric emission produced in the decay of these isomers in a larger volume surrounding the core and show that it can explain the H.E.S.S. flux while being in agreement with the spatially extended emission region recently reported.

Speaker: Leonel Raul Morejon (Z_THAT (Theoretische Astroteilchenphysik))
• 73
Features of a single source describing the very end of the energy spectrum of cosmic rays

The energy spectrum of cosmic rays extends over many orders of magnitude with a steep suppression of the flux at the highest energies. The energy spectrum of ultra-high energy cosmic rays (UHECR) is measured with great precision by the Pierre Auger Observatory (Auger) and Telescope Array. However, the two measured spectra show different slopes of the decrease at the highest energies. This disagreement can be caused by the ability of these two experiments to see different parts of the night sky and, therefore, in principle, different sources of UHECR as well. In our study, we investigate the possibility that the energy spectrum measured by Auger at energies above $log(E/eV)\geq19.5$ could be explained by a dominant single strong source. We explore the space of possible features of such a source including its distance, spectral index and mass composition, and compare the resulting flux after propagation using simulations within CRPropa 3 with the data measured by Auger. No restrictions are made on the measurement of shower maximum tightly connected with the mass composition due to large uncertainties at the highest energies. We show the possible parameters of such a source and explore possible mass composition mixes that could explain the data well.

Speaker: Alena Bakalova (FZU - Institute of Physics of the Czech Academy of Sciences)
• 74
Transient Source for the Highest Energy Galactic Cosmic Rays

We analyze the Auger dipole anisotropy measurements below 8 EeV, to expose the existence of an individual source of the Galactic cosmic rays above $10^{17}$ eV. The source is incompatible with being in the direction of the Galactic center by a $\chi^2$/dof > 6. Interpreting the amplitude and direction of the Galactic HE Dipole in terms of a transient, we find:
a) The amplitude of the Galactic VHE dipole constrains the ratio of source distance and time since the transient event occurred.
b) The Galactic VHE dipole is compatible with production in a transient event in the Galactic plane which occurred about 30 kyr ago at a distance of about 1 kpc. A SN remnant and pulsar consistent with being the relics of this event are identified.
c) The peak rigidity of these VHE Galactic CRs is about 0.1 EV.
d) For reasonable estimates of the diffusion coefficient of the GMF, the energy emitted in CRs above 100 PeV by the transient Galactic source is about $10^{44-45}$ ergs —compatible with acceleration in the converging-flow shock of a core-collapse supernova exploding into the wind of a massive binary companion.

The estimated rate of such events in the Galaxy as a whole is compatible with the inferred space-time separation of this event. Comparable transient events in galaxies throughout the Universe may be an important source of astrophysical neutrinos. Implications and tests of this hypothesis for the origin of the highest energy Galactic cosmic rays will be discussed.

Speaker: Glennys Farrar (New York University)
• Discussion: 15 Future instrumentation | CRD-MM 06

#### 06

• 75
The Roadmap to the POEMMA Mission

The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) is designed to observe ultrahigh-energy cosmic rays (UHECRs) and cosmic neutrinos from space with sensitivity over the full celestial sky. Developed as a NASA Astrophysics Probe-class mission, POEMMA consists of two identical telescopes orbiting the Earth in a loose formation that observe extensive air showers (EAS) via air fluorescence and Cherenkov emissions. UHECRs and UHE neutrinos above 20 EeV are observed with the stereo fluorescence technique, while tau neutrinos above 20 PeV are observed via the optical Cherenkov signals produced by up-going EAS produced by the decay of Earth-emerging tau-leptons. The POEMMA satellites are designed to quickly re-orientate to follow up transient cosmic neutrino sources and obtain unparalleled neutrino flux sensitivity.
Both observation techniques and the instrument design are being validated by current and upcoming missions, such as Mini-EUSO and EUSO-SPB as part of the JEM-EUSO program, and Terzina SmallSat mission. We will discuss the POEMMA science performance and the current roadmap to the POEMMA mission.

Speaker: Prof. Angela V. Olinto (The University of Chicago)
• 76
Cosmic-ray isotope measurements with HELIX

Recent discoveries of new features in Galactic cosmic-ray fluxes emphasize the importance of understanding the propagation of cosmic rays. HELIX (High Energy Light Isotope eXperiment) is designed to improve the measurements of light cosmic-ray isotopes, including the propagation clock isotope $^{10}\mathrm{Be}$ and stable secondary isotope $^{9}\mathrm{Be}$, which will be essential to study the propagation of the cosmic rays. The magnetic spectrometer of HELIX consists of a 1 Tesla superconducting magnet containing a high-resolution gas drift chamber as a tracking detector and two velocity measuring detectors: a time-of-flight detector and a ring-imaging Cherenkov detector. While the HELIX instrument can measure the fluxes of the light isotopes from protons (Z=1) up to neon (Z=10), it is optimized to study the flux of beryllium isotopes from 0.2 GeV/n to beyond 3 GeV/n with a sufficient mass resolution to discriminate between $^{10}\mathrm{Be}$ and $^{9}\mathrm{Be}$. In this talk, I will review the scientific goals and the design of the instrument and report its current status and project plans.

Speaker: Nahee Park (Queen's University)
• 77
The TIGERISS instrument

TIGERISS ( Trans-Iron Galactic Element Recorder for the International Space Station) is a natural evolution to space of the balloon-borne TIGER and SuperTIGER instruments discussed elsewhere at this conference. TIGERISS will be proposed to the next NASA Pioneers opportunity, anticipated in September 2021, as an ISS-attached mission to extend measurements of the relative abundances of galactic cosmic-ray nuclei to the Pt-Pb region with individual element resolution and excellent statistical precision. TIGERISS is designed to accurately determine the atomic number of incident nuclei to beyond the end of the periodic table and to begin measurements at a low-Z trigger threshold, planned for between He and C in order to measure the velocity distributions of the more common species using its Cherenkov detectors. TIGERISS measures the atomic number of incident nuclei by both the differential ionization energy loss (dE/dX) vs. Cherenkov (velocity) technique and the Cherenkov vs. Cherenkov technique using acrylic and silica-aerogel Cherenkov detectors as in TIGER and SuperTIGER. However, it utilizes silicon strip detectors for dE/dX and trajectory measurements, replacing the plastic scintillators and scintillating fiber hodoscopes of TIGER and SuperTIGER. The scientific goals and anticipated results of TIGERISS are discussed in an accompanying paper at this conference. Here we give the details of the TIGERISS measurement technique and its technical implementation.

Speaker: John Mitchell (NASA Goddard Space Flight Center)
• 78
The High Energy Particle Detector (HEPD-02) for the second China Seismo-Electromagnetic Satellite (CSES-02)

The CSES (China Seismo-Electromagnetic Satellite) is a multi-instrumental scientific space program whose objectives are to investigate the near-Earth electromagnetic, plasma and particle environment and for studying the seismo associated disturbances in the ionosphere-magnetosphere transition zone, the anthropogenic electromagnetic noise as well as the natural non-seismic electromagnetic emissions, mainly due to tropospheric activity. In particular, the mission aims at confirming the existence of possible temporal correlations between the occurrence of earthquakes for medium and strong magnitude and the observation in space of electromagnetic perturbations, plasma variations and precipitation of bursts of high-energy charged particles from the inner Van Allen belt.
The first satellite (CSES-01) was launched on 2018, while a second one (CSES-02) is currently under development and its launch is expected by 2022. As in CSES-01, the suite of instruments on-board CSES-02 will comprise a particle detector (HEPD-02, High-energy Particle Detector) to measure the increase of the electron and proton fluxes due to short-time perturbations of the radiation belts induced by solar, terrestrial, or anthropic phenomena in the energy range 3-100 MeV for electrons and 30-200 MeV for protons.
HEPD-02 comprises a tracker made of CMOS Monolithic Active Pixel Sensors (MAPS), a double layer of crossed plastic scintillators for trigger and a calorimeter, made of a tower of plastic scintillators and a matrix of inorganic crystals, surrounded by plastic scintillator veto planes. We present the main characteristics and performance of HEPD-02, highlighting the architectural choices made to meet the scientific objectives of the mission.

Speaker: Dr Cristian De Santis (INFN Sezione di Roma Tor Vergata)
• Discussion: 29 Outreach online | O&E 07

#### 07

• 79
Armagh Observatory and Planetarium's Outreach Programme for the Cherenkov Telescope Array

We describe an outreach programme being undertaken at the Armagh Observatory and Planetarium (AOP) for the Cherenkov Telescope Array (CTA). Founded in 1790 and with a rich astronomical heritage, AOP today combines the research and education arms of our organisation to bring a research-informed outreach programme to the public, most often through our planetarium-related activities.

We have developed and written, in-house, a short (10 minute) Full Dome planetarium show ("Exploring the High-Energy Universe") that describes the science of gamma-ray astronomy and introduces the CTA as the as the first ground-based gamma-ray observatory open to scientific communities. This dome show will be made freely and publicly available through the Digistar cloud to other planetaria. It may be rendered into other formats for other planetarium projector systems. We will explain how we undertook this project and consider how it might be extended to provide outreach material for other science facilities.

In parallel, we are engaged in developing a series of short videos to introduce the scientists and the science of the UK CTA consortium, again designed for public audiences. These videos can be accessed through our social media channels. Delivery of such outreach programme in byte-sized pieces is an essential element in attracting and engaging audiences. We explain how we have developed the skill set to do this in our Education Team at AOP whilst our facility has been closed for the past year, a result of the Covid-pandemic.

Speaker: Michael Burton (Armagh Observatory and Planetarium)
• 80
Multi-messenger Astroparticle Physics for the Public via the astroparticle.online Project

Many projects want to share knowledge on particle and astroparticle physics (in particular, cosmic ray physics), however multi-messenger astroparticle-physics is still a young research field and hardly covered in educational curricula or in outreach. The astroparticle.online project, founded in 2018 within the framework of the German-Russian Astroparticle Data Life Cycle Initiative (GRADLCI), encompasses an endeavor to address this issue.
Within the project, scientists from Karlsruhe Institute of Technology (KIT), Irkutsk State University (ISU) and Moscow State University (MSU) developed a range of educational materials: articles, video lectures, tests, problems to solve, laboratory works and pre-trained neural networks for particle recognition. The project is supported by the KASCADE Cosmic-ray Data Center (KCDC) and GRADLCI data aggregation platform, where one can retrieve and analyze open scientific data from various experiments..
The main audience of the project’s activities are high school and undergraduate students. All the educational materials are available online at the project's web portal https://www.astroparticle.online/, they are used both in online and offline masterclasses organized by the project members, and also as the supplementary content by educational organizations - for example, in the ISU course 'Introduction to experimental methods in high energy astrophysics'. Over the time that the project has been operating, more than 120 students took part in its activities.
This contribution will cover the experience gained while running the project for more than 3 years now, our challenges, developments and future plans.

Speaker: Victoria Tokareva (KIT)
• 81
Outreach activities at the Pierre Auger Observatory

The Pierre Auger Observatory, sited in Malargüe, Argentina, is the largest observatory available for measuring ultra-high-energy cosmic rays (UHECR).  The Auger Collaboration has measured and analysed an unprecedented number of UHECRs. Along with making important scientific discoveries, for example, the demonstration that cosmic rays above 8 EeV are of extragalactic origin and the observation of a new feature in the energy spectrum at around 13 EeV, outreach work has been carried out across the 17 participating countries and online.  This program ranges from talks to a varied audience, to the creation of a local Visitor Center, which attracts ~8000 visitors annually, to initiating masterclasses.  Permanent and temporary exhibitions have been prepared both in reality and virtually.  Science fairs for elementary- and high-school students have been organised, together with activities associated with interesting phenomena such as eclipses.  In addition, we participate in international events such as the International Cosmic Day, Frontiers from H2020, and the International Day of Women and Girls in Science. Part of the Collaboration website is aimed at the general public. Here the most recent articles published are summarised. Thus the Collaboration informs people about work in our field, which may seem remote from everyday life. Furthermore, the Auger Observatory has been a seed for scientific and technological activities in and around Malargüe. Different outreach ventures that already have been implemented and others which are foreseen will be described.

Speaker: Karen Salomé Caballero Mora (Universidad Autónoma de Chiapas)
• 82
Virtual tours to the KATRIN experiment

The KArlsruhe TRItium Neutrino (KATRIN) experiment performs a model-independent measurement of the electron neutrino mass with a design sensitivity of 0.2 eV (90% CL) after three full years of measurement time. KATRIN measures near the endpoint of the tritium beta spectrum, using the MAC-E filter principle by virtue of its 70 m long beamline. Its technological challenges include the high-luminosity tritium source, the cryogenic pumping section and the 20 m long ultra-high vacuum vessel of the main spectrometer.

Guided tours to the KATRIN beamline with supporting presentations are frequently offered to make the experiment, astroparticle physics and scientific research in general accessible to the public and students in particular. However, the on-site access is limited by the operation of high voltage and magnets, safety regulations for the tritium laboratory and the ongoing pandemic. This fuelled the development of three virtual presentation tools:
a 40-minute-long video tour with live commentary via zoom was created using cellphone-made footage of the beamline and archive footage of the transport and commissioning of its key components;
a 3D panorama of five locations at the beamline for virtual reality headsets or browsers providing a live-action guide or free exploration was developed with the NaWik (National Institute for Science Communication);
and a browser interface for a low-poly model of the full beamline is work-in-progress.
In this talk, we will present all three tools and their making, including first results of the NaWik-research on the knowledge transfer potential of the 3D panorama.

Supported by BMBF (Ø05A20VK3), the Helmholtz Association, the Klaus Tschira Foundation, the KIT centre KCETA, and the Excellence Strategy of the German Federal and State Governments.

Speaker: Dr Manuel Klein (KIT)
• 83
The online laboratories for OCRA - Outreach Cosmic Ray Activities INFN project

OCRA – Outreach Cosmic Ray Activities was born in 2018 as a national outreach project of INFN with the aim of collecting, within a national framework, the numerous public engagement activities in the field of cosmic ray physics already present at a local level in the divisions and laboratories. Since spring of 2020 OCRA offers also a series of online laboratories on its website https://web.infn.it/OCRA/, designed not only to be used by students individually but also to be offered in the classroom by teachers.
The cosmic rays path present on the website will be presented together with the online laboratories on the measurement of muons, from the one related to the dependence on the zenith angle made during the International Cosmic Day up to measurements of the flux dependency on the altitude in the atmosphere and in the water. Also, a laboratory allowing to analyze public data of the Pierre Auger Observatory will be presented. In addition, some teaching methods included in the "Teachers' area" of the OCRA website will be described.
The developed cosmic ray path was also used to organize an online course for teachers of Italian high schools with the purpose of accompanying teachers when approaching the subject for the first time. About 70 teachers participated for a total of 9 lessons.

Speaker: Dr Carla Aramo (INFN Napoli)
• 84
Neutrino Education, Outreach and Communications Activities: Captivating Examples from IceCube

The IceCube Neutrino Observatory at the South Pole has tremendous emotional appeal—the extreme Antarctic environment coupled with the aura of a pioneering experiment that explores the universe in a new way. However, like with most cutting-edge experiments, it is still challenging to translate the exotic, demanding science into accessible language. We present three examples of recent successful education, outreach, and communication activities that demonstrate how we leverage efforts and sustain connections to produce engaging results. We describe our participation in the PolarTREC program that pairs researchers with educators to provide deployments in the Antarctic and how we have sustained relationships with these educators to produce high quality experiences to reach target audiences even during a pandemic. We focus on three examples from the last year: a summer enrichment program for high school students that was also modified for a 10-week IceCube after school program, a virtual visit to the South Pole for the ScienceWriters 2020 conference, and a series of short videos in English and Spanish suitable for all ages that explain traveling, living, and working at the South Pole.

• 85
The Fermi Masterclass Online Edition 2020

The Fermi Masterclass is an international outreach event designed to give high-school students the unique opportunity to discover the world of High-Energy Astrophysics. Since 2017, various Italian universities and research institutes, guided by the National Institute for Nuclear Physics (INFN), organized a "full immersion" day of dedicated lectures and exercises in which students analysed real data collected by the LAT experiment aboard the Fermi satellite. Over the years, foreign institutes from Slovenia, Sweden and the U.S. also joined the effort, giving the students the unique opportunity to interact with each other as in real international collaborations.
The 4th edition of the Fermi Masterclass was scheduled to take place in April 2020. However, due to the pandemic emergency, the Masterclass was initially postponed, and finally took place as an online edition on December 10th, 2020.
Here we present the structure and organization of this first virtual event, including an interactive part of exercises accessible to the students through dedicated web platforms.

Speaker: Silvia Raino (Dipartimento Interateneo di Fisica "M.Merlin", Università di Bari and INFN-Bari (ITALY))
• 86
#meetTheMAGICians: Science communication and visibility of young researchers

Among the many activities organized by the Outreach working group of the MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) Collaboration, we would like to present the ongoing project #meetTheMAGICians. Under this hashtag, used on our social media pages (@MAGICtelescopes), we collect live streaming events on astroparticle physics topics, series of social media posts, videos and other contents. In addition to increasing the visibility of the MAGIC collaboration, a central goal of #meetTheMAGICians is to strongly connect the communication of our science to the individual achievements of our researchers. It is a community-wide challenge to increase the individual recognition of early career scientists in large international science collaborations. In this project, we give young members of the MAGIC collaboration the chance to increase their visibility in the astroparticle community by highlighting their individual contributions to our research. At the same time, we aim to communicate to the general public how exciting and diverse astroparticle physics can be, and to stimulate in young students the curiosity towards the extreme Universe. We will present an overview on the present status of the project, and an analysis of both successes and remaining challenges.

Speaker: Juliane van Scherpenberg (Max-Planck-Institut for Physics)
• 87
2’ science: A Science Communication Project for Astrophysics

Two-minute science (2'science) is a science communication project supported by early-career Greek astrophysicists. With this endeavor, which started in December 2020, we try to bridge the gap between the scientific community and the public. This project is based on the simple idea of writing short articles with an approximate reading time of two minutes. These articles cover several topics and their difficulty scales to cover a broad audience range, from young students to experienced adults. We support the idea of “ask an expert” in astrophysics in Greece, where any reader can pose a question. We offer the appropriate answer either by writing it ourselves or by contacting the field experts from the Greek astronomical society. Furthermore, our previous science communication experience leads us to design educational activities for students and/or adults based on pedagogical means. A successful one was an “escape-zoom” titled “Escape to Other Worlds”, a digital version of an escape room. Further activities are astronomy workshops for teenagers, online talks to schools, and our participation in a scientific podcast to trigger the public interest in astrophysics. We communicate this work through social media, where several thousands of people already follow our work.

Speaker: Dimitrios Kantzas (UvA)
• 88
Astronomy Outreach and Education in Namibia: H.E.S.S. and beyond

Astronomy plays a major role in the scientific landscape of Namibia. Because of its excellent sky conditions, Namibia is not only frequently visited by astrophotographers but is also home to ground-based observatories like the High Energy Spectroscopic System (H.E.S.S.), in operation since 2002. Located near the Gamsberg mountain, H.E.S.S. performs groundbreaking science by detecting very-high-energy gamma-rays from many different objects. The fascinating stories behind many of them are featured regularly in the “Source of the Month”, a blog-like format intended for the general public with more than 170 features so far. Together with this digital format, H.E.S.S. outreach activities have always been covered locally, e.g. via ‘open days’ and guided tours on the H.E.S.S. site itself. An overview of the H.E.S.S. outreach activities will be presented in this contribution, along with discussions relating to the current landscape of astronomy outreach and education in Namibia. We will also touch on some of the significant activity in the country in recent months, which aims to use astronomy as a means for capacity-building and sustainable development. Finally, as we take into account the future prospects of radio astronomy in the country, momentum for a wider range of astrophysics research is clearly building – this presents a great opportunity for the astronomy community to come together to capitalise on this movement and further support astronomy outreach and education in Namibia.

Speaker: Dr Hannah Dalgleish (University of Oxford; University of Namibia)
• Discussion: 32 Cherenkov Media & Detector Calibration | NU 05

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• 89
A calibration study of local ice and optical sensor properties in IceCube

The optical sensors of the IceCube Neutrino Observatory are attached on vertical strings of cables. They were frozen into the ice in the deployment holes made by hot water drill. This hole ice, to the best of our knowledge, consists of a bubbly central column, with the remainder of the re-frozen volume being optically clear. The bubbly ice often blocks one or several of the calibration LEDs in every optical sensor and significantly distorts the angular profile of the calibration light pulses. It also affects the sensors’ response to in-coming photons at different locations and directions. We present our modeling of the hole ice optical properties as well as optical sensor location and orientation within the hole ice. The shadowing effects of cable string and possible optical sensor tilt away from the nominal vertical alignment are also discussed.

• 90
Deployment of the IceCube Upgrade Camera System in the SPICEcore hole

IceCube is a cubic-kilometer scale neutrino telescope located at the geographic South Pole. The detector utilizes the extremely transparent Antarctic ice as a medium for detecting Cherenkov radiation from neutrino interactions. While the optical properties of the glacial ice are generally well modeled and understood, the uncertainties which remain are still the dominant source of systematic uncertainties for many IceCube analyses. A camera and LED system is being built for the IceCube Upgrade that will enable the observation of optical properties throughout the Upgrade array. The SPICEcore hole, a 1.7 km deep ice-core hole located near the IceCube detector, has given the opportunity to test the performance of the camera system ahead of the Upgrade construction. In this contribution, we present the results of the camera and LED system deployment during the 2019/2020 austral summer season as part of a SPICEcore luminescence logger system.

Speaker: Mr Danim Kim (Sungkyunkwan University)
• 91

The IceCube Neutrino Observatory at the geographic South Pole instruments a gigaton of glacial Antarctic ice with over 5000 photosensors. The detector, by now running for over a decade, will be upgraded with seven new densely instrumented strings. The project focuses on the improvement of low-energy and oscillation physics sensitivities as well as re-calibration of the existing detector. Over the last few years we developed a precision optical calibration module (POCAM) providing self-monitored isotropic nanosecond light pulses for optical calibration of large-volume detectors. Over 20 next-generation POCAMs will be calibrated and deployed in the IceCube Upgrade in order to reduce existing detector systematics. We report a general overview of the POCAM instrument, its performance and calibration procedures, as well as simulation studies to estimate its anticipated physics impact.

Speaker: Nikhita Khera (Technical University of Munich)
• 92
Design, performance, and analysis of a measurement of optical properties of antarctic ice below 400 nm

The IceCube Neutrino Observatory, located at the geographic South Pole, is the world's largest neutrino telescope, instrumenting 1 km³ of Antarctic ice with 5160 photosensors to detect Cherenkov light. For the IceCube Upgrade, to be deployed during the 2022-23 polar field season, and the enlarged detector IceCube-Gen2 several new optical sensor designs are under development. One of these optical sensors, the Wavelength-shifting Optical Module (WOM), uses wavelength-shifting and light-guiding techniques to measure Cherenkov photons in the UV-range from 380 to 250 nm. In order to understand the potential gains from this new technology, a measurement of the scattering and absorption lengths of UV light was performed in the SPICEcore borehole at the South Pole during the winter seasons of 2018/2019 and 2019/2020. For this purpose, a calibration device with a UV light source and a detector using the wavelength shifting technology was developed. We present the design of the developed calibration device, its performance during the measurement campaigns, and the best fit comparing the data to a Monte Carlo simulation.

Speaker: Jannes Brostean-Kaiser (Z_ICE (IceCube+NG))
• 93
The Acoustic Module for the IceCube Upgrade

The IceCube Neutrino Observatory will be upgraded with more than 700 additional optical sensor modules and new calibration devices. Improved calibration will enhance IceCube’s physics capabilities both at low and high neutrino energies. An important ingredient for good angular resolution of the observatory is precise calibration of the positions of optical sensors. Ten acoustic modules, which are capable of receiving and transmitting acoustic signals, will be attached to the strings. These signals can additionally be detected by compact acoustic sensors inside some of the optical sensor modules. With this system we aim for calibration of the detectors’ geometry with a precision better than 10 cm by means of trilateration of the arrival times of acoustic signals. This new method will allow for an improved and complementary geometry calibration with respect to previously used methods based on optical flashers and drill logging data. The longer attenuation length of sound compared to light makes the acoustic module a promising candidate for IceCube-Gen2, which may have optical sensors on strings with twice the current spacing. We present an overview of the technical design and tests of the system as well as analytical methods for determining the propagation times of the acoustic signals.

Speaker: Mr Christoph Günther (III. Physikalisches Institut B, RWTH Aachen University)
• 94
Monitoring of optical properties of deep lake water

We present the results of the one year monitoring of absorption and scattering lengths of light with wave length 375÷532nm within the effective volume deep of underwater neutrino telescope Baikal-GVD, which were measured by a device «BAIKAL-5D». The «BAIKAL-5D» was installed during the 2020y winter expedition at a depth 1250 m. The device has a shaded point-like isotropic light source with spectral resolution about 3nm. A wide angle light receiver is moved by a stepper motor so that the distance between the receiver and the light source changed between 0.9 and 7,4 m. Absorption and scattering lengths were measured every week in 6 spectral points. Shot-time variation of absorption and scattering length was estimated.

Speaker: Evgenii Ryabov (Baikal-collaboration)
• 95
KM3NeT Detection Unit Line Fit reconstruction using positioning sensors data

KM3NeT is constructing two large neutrino detectors in the Mediterranean Sea: KM3NeT/ARCA, located near Sicily and aiming at neutrino astronomy, and KM3NeT/ORCA, located near Toulon and designed for neutrino oscillation studies.
The two detectors, together, will have hundreds of Detection Units (DUs) with 18 Digital Optical Modules (DOMs) maintained vertical by buoyancy, forming a large 3D optical array for detecting the Cherenkov light produced after the neutrino interactions. To properly reconstruct the direction of the incoming neutrino, the position of the DOMs must be known precisely with an accuracy of less than 10 cm, and since the DUs are affected by sea current the position will be measured every 10 minutes.
For this purpose, there are acoustic and orientation sensors inside the DOMs. An Attitude Heading Reference System (AHRS) chip provides the components values of the Acceleration and Magnetic field in the DOM, from which it is possible to calculate Yaw, Pitch and Roll for each floor of the line. A piezo sensor detects the signals from fixed acoustic emitters on the sea floor, so to position it by trilateration.
Data from these sensors are used as an input to reconstruct the shape of the entire line based on a DU Line Fit mechanical model. This poster presents an overview of the KM3NeT monitoring system, as well as the line fit model and its results.

Speaker: Chiara Poirè (Universitat Politécnica de Valéncia)
• 96
Camera Calibration for the IceCube Upgrade and Gen2

An upgrade to the IceCube Neutrino Telescope is currently under construction. For the Upgrade, seven new strings will be deployed in the central region of the 86 string IceCube detector to enhance the capability to detect neutrinos in the GeV range. One of the main science objectives of the Upgrade is an improved calibration of the IceCube detector to reduce systematic uncertainties related to the optical properties of the ice. We have developed a novel optical camera and illumination system that will be part of 700 newly developed optical modules to be deployed with the Upgrade. A combination of transmission and reflection photographic measurements will be used to measure the optical properties of bulk ice between strings and refrozen ice in the drill hole, to determine module positions, and to survey the local ice environments surrounding the sensor module. In this contribution, we present the production design, acceptance testing, and plan for post-deployment calibration measurements with the camera system.

Speaker: Woosik Kang (Sungkyunkwan University)
• 97
Development of an in-situ calibration device of firn properties for Askaryan neutrino detectors

High energy neutrinos (E>10$^{17}$ eV) are detected cost-efficiently via the Askaryan effect in ice, where a particle cascade induced by the neutrino interaction produces coherent radio emission that can be picked up by antennas installed below the surface. A good knowledge of the firn properties is required to reconstruct the neutrino properties. In particular, a continuous monitoring of the snow accumulation (which changes the depth of the antennas) and the index-of-refraction profile are crucial for an accurate determination of the neutrino's direction and energy. We present an in-situ calibration system that extends the radio detector station with a radio emitter to continuously monitor the firn properties by measuring time differences of direct and reflected (off the surface) signals (D'n'R). We optimized the station layout in a simulation study and quantified the achievable precision. We present 14 months of data of the ARIANNA detector on the Ross Ice Shelf, Antarctica, where a prototype of this calibration system was successfully used to monitor the snow accumulation with unprecedented precision of 1mm. We explore and test several algorithms to extract the D'n'R time difference from noisy data (including deep learning). This constitutes an in-situ test of the neutrino vertex distance reconstruction using the D'n'R technique which is needed to determine the neutrino energy.

Speaker: Mr Jakob Beise (Uppsala Universitet)
• 98
Development of calibration system for a project of a new Baksan Large Neutrino Telescope

We present results of the development of a calibration system for a project of a new Baksan Large Neutrino Telescope. The calibration system is based on fast blue and UV InGaN and AlGaN ultra bright and high power light emitting diodes (LEDs), a diffusing ball and fiber optics. Special fast electronic drivers for such LEDs were developed. The drivers are based on fast complementary and avalanche transistors. The diffusing ball is designed to provide uniform isotropic illumination of all photomultipliers of the detector. Thorough studies of timing and light yield parameters are done. Special emphasis is done on careful studies of compatibility of calibration system parts with liquid scintillator and ultra pure water.

Speaker: Mr Nikita Ushakov (Institute for Nuclear Research of the Russian Academy of Science, Prospekt 60-letiya Oktyabrya 7a, Moscow 117312, Russia)
• 99
In-situ gain calibration based on single byte PMT signals

Bouke Jung$^1$, Maarten de Jong$^2$, Paolo Fermani$^3$
on behalf of the KM3NeT collaboration

$^1$) University of Amsterdam, Nikhef
bjung@nikhef.nl
$^2$) Leiden University, Nikhef
mjg@nikhef.nl
$^3$) Sapienza Università di Roma
paolo.fermani@roma1.infn.it

Present and foreseen neutrino observatories, such as IceCube, P-ONE, GVD, Antares and KM3NeT have to operate in challenging environments, where high count rates go hand in hand with limited bandwidths.
To keep the data rates in these experiments within the allowed range, rigorous data reduction is essential.
At the same time, sufficient information needs to be recorded to accurately measure the neutrino properties.
The KM3NeT collaboration has developed a novel data acquisition procedure, in which each PMT signal is reduced to a datapacket of 6 Bytes, containing the PMT identifier (1 B), the hit time (4 B) and the duration over which the associated PMT pulse exceeded the threshold (1B).
This talk highlights an analytical pulse-shape model which is used to perform in-situ calibrations of the gain and its spread, using only the time-over-threshold statistics associated with single photon hits.

Speaker: Bouke Jung (Nikhef and University of Amsterdam)
• 100
Luminescence of ice as a new detection channel for neutrino telescopes

Natural water and ice are currently used as optical detection media in large scale neutrino telescopes, such as IceCube, KM3NeT/ANTARES and GVD. When charged particles, such as those produced by high energy neutrino interactions, pass through ice or water at relativistic speeds they induce Cherenkov light emission. This is detected by the optical modules of neutrino telescopes. However, slower moving particles, including potential exotic matter such as Magnetic Monopoles or Q-balls, cannot be detected using this channel.

A new kind of signature can be detected by using light emission from luminescence in water or ice. This detection channel enables searches for exotic particles which are too slow to emit Cherenkov light and currently cannot be probed by the largest particle detectors in the world, i.e. neutrino telescopes. Luminescence light is highly dependent on the ice structure, impurities, pressure and temperature which demands a comprehensive study.

Luminescence light is induced by highly ionizing particles passing through a medium and exciting the surrounding matter. To utilise this new detection channel in neutrino telescopes, laboratory measurements using water and ice as well as an in-situ measurement in Antarctic ice were performed. The experiments as well as the measurement results will be presented covering light yields, spectra and decay times. The impact on searches for new physics with neutrino telescopes will be discussed.

Speaker: Dr Anna Pollmann (Universität Wuppertal)
• 101
Method and device for tests of the laser optical calibration system for the Baikal-GVD underwater neutrino Cherenkov telescope

The large-scale deep underwater Cherenkov neutrino telescopes like Baikal-GVD, ANTARES or KM3NeT, require calibration and testing methods of their optical modules. These methods usually include laser-based systems which allow to check the telescope responses to the light and for real-time monitoring of the optical parameters of water such as absorption and scattering lengths, which show seasonal changes in natural reservoirs of water. We will present a testing method of a laser calibration system and a set of dedicated tools developed for BaikalGVD, which includes a specially designed and built, compact, portable, and reconfigurable scanning station. This station is adapted to perform fast quality tests of the underwater laser sets just before their deployment in the telescope structure. The testing procedure includes the energy stability test of the laser device, 3D scan of the light emission from the diffuser and attenuation test of the optical elements of the laser calibration system. The test bench consists primarily of an automatic mechanical scanner with a movable Si detector, beam splitter with a reference Si detector and, optionally, Q-switched diode-pumped solid-state laser used for laboratory scans of the diffusers. The presented test bench enables a three-dimensional scan of the light emission from diffusers, which are designed to obtain the isotropic distribution of photons around the point of emission. The results of the measurement can be easily shown on a 3D plot immediately after the test and may be also implemented to a dedicated program simulating photons propagation in water, which allows to check the quality of the diffuser in the scale of the Baikal-GVD telescope geometry.

Speaker: Mr Konrad Kopański (The H. Niewodniczański Institute of Nuclear Physics Polish Academy of Sciences)
• 102
Positioning system for Baikal-GVD

Baikal-GVD is a kilometre scale neutrino telescope currently under construction in Lake Baikal. Due to water currents in Lake Baikal, individual photomultiplier housings are mobile and can drift away from their initial position. In order to accurately determine the coordinates of the photomultipliers, the telescope is equipped with an acoustic positioning system. The system consists of a network of acoustic modems, installed along the telescope strings and uses acoustic trilateration to determine the coordinates of individual modems. This contribution discusses the current state of the positioning in Baikal-GVD, including the recent upgrade to the acoustic modem polling algorithm.

Speaker: Mr Alexander Avrorin (INR RAS)
• 103
The Calibration Units of KM3NeT : multi-purpose calibration devices

KM3NeT is a deep-sea infrastructure composed of two neutrino telescopes being deployed in the Mediterranean Sea : ARCA, near Sicily in Italy, designed for neutrino astronomy and ORCA, near Toulon in France, designed for neutrino oscillations. These two telescopes are 3D arrays of optical modules used to detect the Cherenkov radiation, which is a signature of charged particles created in the neutrino interaction and propagating faster than light in the sea water.

To achieve the best performance for the event reconstruction in the telescopes, the exact location of the optical modules, affected by the sea current, must be known at any time and the timing resolution between optical modules must reach the sub-nanosecond level. Moreover, the properties of the environment, in which the telescopes are deployed, such as temperature and salinity, are continuously monitored to allow best modelling of the acoustic signal propagation in the water.

KM3NeT is going to deploy several dedicated Calibration Units hosting instruments dedicated to meet these calibration goals. The Calibration Base will host a Laser Beacon for time calibration and a long-baseline acoustic emitter and a hydrophone, which are part of the positioning system for the optical modules. Some of these Calibration Units will also be equipped with an Instrumentation Unit hosting environmental monitoring instruments.

This poster describes all the devices, features and purposes of the Calibration Units, with a special emphasis on the first such unit that will be deployed on the ORCA site in 2021.

Speaker: Rémy Le Breton (APC)
• Discussion: 52 Analysis, Methods, Catalogues, Community Tools, Machine Learning... | GAD-GAI 04

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• 104
Classification of Fermi-LAT sources with deep learning

Machine learning techniques are powerful tools for the classification of unidentified gamma-ray sources. We present a new approach based on dense and recurrent deep neural networks to classify unidentified or unassociated gamma-ray sources in the last release of the Fermi-LAT catalog (4FGL-DR2). Our method uses the actual measurements of the photon energy spectrum and time series as input for the classification, instead of specific, hand-crafted features. We focus on different classification tasks: the separation between extragalactic sources, i.e. Active Galactic Nuclei (AGN), and Galactic pulsars, the further classification of pulsars into young and millisecond pulsars and the sub-classification of AGN into different types. Since our method is very flexible, we generalize it to include multiwavelength data on the energy and time spectra coming from different observatories, as well as to account for uncertainties in the measurements and in the predicted classes. Our list of high-confidence candidate sources labelled by the neural networks provides targets for further multiwavelength observations to identify their nature, as well as for population studies.

Speaker: Dr Silvia Manconi (Institute for Theoretical Particle Physics and Cosmology, RWTH Aachen)
• 105
Detection methods for the Cherenkov Telescope Array at very-short exposure times

The Cherenkov Telescope Array (CTA) will be the next generation ground-based observatory for very-high-energy gamma-ray astronomy, with the deployment of tens of highly sensitive and fast-reacting Cherenkov telescopes. It will cover a wide energy range (20 GeV - 300 TeV) with unprecedented sensitivity. Our study is focused on real-time detection at very-short timescales (from 1 to 100 seconds). We built and characterised an analysis and detection pipeline and tested it via the verification of the Wilks’ theorem for false-positives. The performance was evaluated in terms of sky localisation accuracy, detection significance and detection efficiency for different observing and analysis configurations. Our goal is to determine the feasibility of the analysis methods at very-short exposure times. We also investigated the sensitivity degradation which is expected in a real-time analysis context and compared it to the requirement of being better than half of the CTA sensitivity. In this work, we present a general overview of the pipeline and the performance obtained for the use-case of a blind-search and detection following an external alert, such as from a gamma-ray burst or a gravitational wave event.

Speaker: Ambra Di Piano (INAF/OAS Bologna)
• 106
Application of Pattern Spectra and Convolutional Neural Networks to the Analysis of Simulated Cherenkov Telescope Array Data

The Cherenkov Telescope Array (CTA) will be the next generation gamma-ray observatory with more than 100 telescopes located in the northern and southern hemispheres. It will be the major global instrument for very high energy astronomy over the next decade, offering one order of magnitude better flux sensitivity than current generation ground-based gamma-ray telescopes. Each telescope will provide a snapshot of gamma-ray induced particle showers by capturing their Cherenkov emission at ground level. The simulation of such events provides images that can be used as training data for Convolutional Neural Networks (CNNs) to determine the energy and direction of the initial gamma rays. Compared to other state-of-the-art algorithms, analyses based on CNNs promise to further enhance the performance to be achieved by CTA.
Pattern spectra are commonly used tools for image classification and provide the distributions of the shapes and sizes of various objects comprising an image. The use of relatively shallow CNNs on pattern spectra would automatically select relevant combinations of features within an image, taking advantage of the 2D nature of pattern spectra. In this work, we will generate pattern spectra from simulated gamma-ray events instead of using the raw images themselves in order to train our CNN for energy and arrival direction reconstruction. This is different from other relevant learning and feature selection methods that have been tried in the past. Thereby, we aim to reduce the depth of our neural network to obtain a significantly faster and less computationally intensive algorithm, with minimal loss of performance.

Speaker: Jann Aschersleben
• 107
Source-morphology-independent background estimation for extended gamma-ray sources

We present a new background estimation method for a search for largely extended TeV gamma-ray sources with instruments using the imaging atmospheric Cherenkov technique. This novel method does not rely on the assumption of source morphology and uses the cosmic-ray-like events (events that fail gamma-hadron-separation cuts using shower-shape parameters) collected from the given field to estimate the gamma-ray-like background of the same field. We show that the use of cosmic-ray-like events allows an effective reduction of the systematic error on background subtraction. This report explains the methodology, presents the validation of the background method using the gamma-ray-free VERITAS (Very Energetic Radiation Imaging Telescope Array System) dark field data, and includes comparisons with conventional background methods. This new method is suitable for largely extended gamma-ray sources whose angular sizes exceed the capacity of the conventional background methods.

Speaker: Ruo Yu Shang (University of California, Los Angeles)
• 108
Analysis of the Cherenkov Telescope Array first Large Size Telescope real data using convolutional neural networks

The Cherenkov Telescope Array (CTA) is the future ground-based gamma-ray observatory and will be composed of two arrays of imaging atmospheric Cherenkov telescopes (IACTs) located in the Northern and Southern hemispheres respectively. The first CTA prototype telescope built on-site, the Large Size Telescope (LST-1), is under commissioning in La Palma and has already taken data on numerous known sources.
IACTs detect the faint flash of Cherenkov light indirectly produced after a very energetic gamma-ray photon has interacted with the atmosphere and generated an atmospheric shower. Reconstruction of the characteristics of the primary photons is usually done using a parameterization up to the third order of the light distribution of the images.
In order to go beyond this classical method, new approaches are being developed using state-of-the-art methods based on convolutional neural networks (CNN) to reconstruct the properties of each event (incoming direction, energy and particle type) directly from the telescope images. While promising, these methods are notoriously difficult to apply to real data due to differences (such as different levels of night sky background) between Monte Carlo (MC) data used to train the network and real data.
The GammaLearn project, based on these CNN approaches, has already shown an increase in sensitivity on MC simulations for LST-1 as well as a lower energy threshold. In this work, we apply the GammaLearn network to real data acquired by LST-1 and compare the results to the classical approach that uses random forests trained on extracted image parameters. The improvements on the background rejection, event direction, and energy reconstruction are discussed in this contribution.

Speaker: Thomas Vuillaume (Laboratoire d’Annecy de Physique des Particules, Univ. Grenoble Alpes, Univ. Savoie MontBlanc, CNRS, LAPP)
• 109
Analysis optimisation for more than 10 TeV gamma-ray astronomy with IACTs

The High Energy Stereoscopic System (H.E.S.S.) is one of the currently operating Imaging Atmospheric Cherenkov Telescopes. H.E.S.S. operates in the broad energy range from a few tens of GeV to more than 50 TeV reaching its best sensitivity around 1 TeV. In this contribution, we present an analysis technique, which is optimised for the detection at the highest energies accessible to H.E.S.S. and aimed to improve the sensitivity above 10 TeV. It includes the employment of improved event direction reconstruction and gamma-hadron separation. For the first time, also extensive air showers with event offsets up to 4.5 degrees from the camera center are considered in the analysis, thereby increasing the effective Field-of-View of H.E.S.S. from 5 to 9 degrees. Key performance parameters of the new high-energy analysis are presented and its applicability demonstrated for representative hard-spectrum sources in the Milky Way.

Speaker: Iryna Lypova
• 110
A 3D likelihood analysis for KM2A data

The square kilometer array (KM2A) is the main array of the Large High Altitude Air Shower Observatory (LHAASO), which is the most sensitive gamma-ray detector for energies above a few tens of TeV. We are developing a software pipeline based on the experimental data, Monte-Carlo simulations and the pointing track of the arrays. The pipeline is able to perform 3D (sky images at different energies) fits of KM2A data, similar to those used for Fermi-LAT and DAMPE gamma-ray analysis. This 3D likelihood analysis could fit source models of arbitrary morphology to the sky images, and get energy spectra information and detection significances simultaneously. The analysis with this software could give consistent results with those using traditional method.

Speaker: Xiaoyuan Huang
• 111
A maximum-likelihood-based technique for detecting extended gamma-ray sources with VERITAS

Gamma-ray observations ranging from hundreds of MeV to tens of TeV are a valuable tool for studying particle acceleration and diffusion within our galaxy. Supernova remnants, pulsar wind nebulae, and star-forming regions are the main particle accelerators in our local Galaxy. Constructing a coherent physical picture of these astrophysical objects requires the ability to distinguish extended regions of gamma-ray emission, the ability to analyze small-scale spatial variation within these regions, and methods to synthesize data from multiple observatories across multiple wavebands. Imaging Atmospheric Cherenkov Telescopes (IACTs) provide fine angular resolution (<0.1 degree) for gamma-rays above 100 GeV. Typical data reduction methods rely on source-free regions in the field of view to estimate cosmic-ray background. This presents difficulties for sources with unknown extent or those which encompass a large portion of the IACT field of view (3.5 degrees for VERITAS). Maximum-likelihood-based techniques are well-suited for analysis of fields with multiple overlapping sources, diffuse background components, and combining data from multiple observatories. Such methods also offer an alternative approach to estimating the IACT cosmic-ray background and consequently an enhanced sensitivity to largely extended sources. In this proceeding, we report on the current status and performance of a maximum likelihood technique for the IACT VERITAS. In particular, we focus on how our method’s framework employs a dimension for gamma-hadron separation parameters in order to improve sensitivity on extended sources.

Speaker: Alisha Chromey (VERITAS Collaboration)
• 112
Bayesian Deep Learning for Shower Parameter Reconstruction in Water Cherenkov Detectors

Deep Learning methods are among the state-of-art of several computer vision tasks, intelligent control systems, fast and reliable signal processing and inference in big data regimes. It is also a promising tool for scientific analysis such as gamma/hadron discrimination.
We present an approach based on Deep Learning for the regression of shower parameters, namely its core position and energy at the ground, using water Cherenkov detectors. We design our method using simulations. In this contribution, we explore the recovery of the shower’s center coordinates. We evaluate the limits of such estimation near the borders of the arrays, including the when the center is outside the detector’s range. We also address the feasibility of recovering other parameters, such as ground energy. We used Bayesian Neural Networks and derived and quantified systematic errors arising from Deep Learning models and optimized the network design. The method could be easily adapted to estimate other parameters.

Speaker: Clecio R. Bom (Centro Brasileiro de Pesquisas Físicas)
• 113
Convolutional Neural Networks for Low Energy Gamma-Ray Air Shower Identification with HAWC

A major task in ground-based gamma-ray astrophysics analyses is to separate events caused by gamma rays from the overwhelming hadronic cosmic-ray background. In this talk we are interested in improving the gamma ray regime below 1 TeV, where the gamma and cosmic-ray separation becomes more difficult. Traditionally, the separation has been done in particle sampling arrays by selections on summary variables which distinguish features between the gamma and cosmic-ray air showers, though the distributions become more similar with lower energies. The structure of the HAWC observatory, however, makes it natural to interpret the charge deposition collected by the detectors as pixels in an image, which makes it an ideal case for the use of modern deep learning techniques, allowing for good performance classifers produced directly from low-level detector information.

Speaker: Ian Watson (University of Seoul)
• 114
Deep Learning Transient Detection with VERITAS

Ground-based gamma-ray observatories such as the VERITAS array of imaging atmospheric Cherenkov telescopes provide insight into very-high-energy (VHE, E>100 GeV) astrophysical transient events. Examples include the evaporation of primordial black holes and gamma-ray bursts. Identifying such an event with a serendipitous location and time of occurrence is difficult. Thus, employing a robust search method becomes crucial. An implementation of a transient detection method based on deep learning techniques for VERITAS will be presented. This data-driven approach significantly reduces the dependency on the characterization of the instrument response and the modelling of the expected transient signal. The response of the instrument is affected by various factors, such as the elevation of the source and the night sky background. The study of these effects allows enhancing the deep learning method with additional parameters to infer their influences on the data. This improves the performance and stability for a wide range of observational conditions. We use our method to investigate archival VERITAS data from 2012 to 2020 for second- to minute-scale VHE transients

Speaker: Konstantin Johannes Pfrang (DESY)
• 115
Deep-learning applications to the multi-objective optimisation of IACT array layouts.

The relative disposition of individual telescopes in the ground is one of the important factors in optimising the performance of a stereoscopic array of imaging atmospheric Cherenkov telescopes (IACTs). Following previous attempts at an automated survey of the broad parameter space involved using evolutionary algorithms, in this paper we will present a novel approach to optimising the array geometry based on deep learning techniques. The focus of this initial work will be to test the algorithmic approach and will be based on a simplified toy model of the array. Despite being simplified, the model heuristics aims to capture the principal array performance features relevant for the layout optimisation. Our final goal is to create an algorithm capable of scanning the large parameter space involved in the design of a large stereoscopic array of IACTs to assist optimisation of the array geometry (in face of external constraints and multiple performance objectives). The use of simple heuristics precludes direct comparison to existing real-world experiments, but the analysis is internally consistent and gives insight as to the potential of the technique. Deep learning techniques are being increasingly applied to tackle a number of problems in the field of Gamma-ray Astronomy, and this work represents a novel, original application of this modern computational technique to the field.

Speaker: Dr Bernardo Fraga (Centro Brasileiro de Pesquisas Físicas)
• 116
Deep-learning-driven event reconstruction applied to simulated data from a single Large-Sized Telescope of CTA

When very-high-energy gamma rays interact high in the Earth’s atmosphere, they produce cascades of particles that induce flashes of Cherenkov light. Imaging atmospheric Cherenkov telescopes (IACTs) detect these flashes and convert them into shower images that can be analyzed to extract the properties of the primary gamma ray. The dominant background for IACTs is comprised of images produced by cosmic hadrons, with typical noise-to-signal ratios of several orders of magnitude. The standard technique adopted to differentiate between images initiated by gamma rays and those initiated by hadrons is based on classical machine learning algorithms, such as Random Forests, that operate on a set of handcrafted parameters extracted from the images. Likewise, the inference of the energy and the arrival direction of the primary gamma ray is performed using those parameters. State-of-the-art deep learning techniques based on convolutional neural networks (CNNs) have the potential to enhance the event reconstruction performance, since they are able to autonomously extract features from raw images, exploiting the pixel-wise information washed out during the parametrization process.

Here we present the results obtained by applying deep learning techniques to the reconstruction of simulated events from a single, next-generation IACT, the Large-Sized Telescope (LST) of the Cherenkov Telescope Array. We use CNNs to separate gamma-ray-induced events from hadronic events and to reconstruct the properties of the former, showing that they perform better than the standard reconstruction technique. Three independent implementations of CNN-based event reconstruction models have been utilized in this work, producing consistent results.

Speaker: Pietro Grespan (INFN Padova Division)
• 117
Development of hybrid reconstruction techniques for TAIGA

The TAIGA-experiment aims to implement a hybrid detection technique of Extensive Air Showers (EAS) at TeV to PeV energies, combining the wide angle Cherenkov timing array HiSCORE with Imaging Air Cherenkov Telescopes (IACTs). The detector currently consists of 89 HiSCORE stations and two IACTs, distributed over an area of about 1 km².
Our goal is to introduce a new reconstruction technique, combining the good angular and shower core resolution of HiSCORE with the gamma-hadron separation power of the imaging telescopes. With the second IACT in operation, three different event types can be explored: IACT stereo, full hybrid (IACT stereo + stations) and mono hybrid (IACT mono + HiSCORE), the latter being the operational goal of TAIGA.
The status of the development of the full hybrid reconstruction and its verification using real data and simulation are presented.

Speaker: Michael Blank (UNI/EXP (Uni Hamburg, Institut fur Experimentalphysik))
• 118
Fast simulation of gamma/proton event images for the TAIGA-IACT experiment using generative adversarial networks

High energy cosmic rays and gamma rays interacting the atmosphere produce extensive air showers (EAS) of secondary particles emitting Cherenkov light. Being detected with a telescope this light forms "images" of the air shower. In the TAIGA project, in addition to images obtained experimentally, model data are widely used. The difficulty is that the computational models of the underlying physical processes are very resource intensive, since they track the type, energy, position and direction of all secondary particles born in EAS. This can lead to a lack of model data for future experiments. To address this challenge, we applied a machine learning technique called Generative Adversarial Networks (GAN) to quickly generate images of two types: from gamma and protons events. As a training set, we used a sample of 2D images obtained using TAIGA Monte Carlo simulation software, containing about 50,000 events. It has been experimentally established that the generation results best fit the training set in the case when for two different types of events we create two different networks and train them separately. For gamma events a discriminator with a minimum number of convolutional layers was required, while for proton events, more stable and high-quality results are obtained if two additional fully connected layers are added to the discriminator. Testing the generators of both networks using third-party software showed that more than 90% of the generated images were found to be correct. Thus, the use of GAN provides reasonably fast and accurate simulations for the TAIGA project.

Speaker: Julia Dubenskaya (Lomonosov Moscow State University)
• 119
Gammapy: a Python Package for Gamma-Ray Astronomy

Gammapy is a community-developed, open source Python package for gamma-ray Astronomy, which is built on the scientific Python ecosystem Numpy, Scipy and Astropy. It provides methods for the analysis of gamma-ray data of many instruments including Imaging Atmospheric Cherenkov Telescopes, Water Cherenkov, as well as space based observatories.

Starting from event lists and a description of the specific instrument response functions (IRF) stored in open FITS based data formats, Gammapy implements the reduction of the input data and instrument response to binned WCS, HEALPix or region based data structures. Thereby it handles the dependency of the IRFs with time, energy as well as position on the sky. It offers a variety of background estimation methods for spectral, spatial and spectro-morphological analysis. Counts, background and IRFs data are bundled in datasets and can be serialised, rebinned and stacked.

Gammapy supports to model binned data using Poisson maximum likelihood fitting. It comes with built-in spectral, spatial and temporal models as well as support for custom user models, to model e.g. energy dependent morphology of gamma-ray sources. Multiple datasets can be combined in a joint-likelihood approach to either handle time dependent IRFs, different classes of events or combination of data from multiple instruments. Gammapy also implements methods to estimate flux points, including likelihood profiles per energy bin, light curves as well as flux and signficance maps in energy bins.

In this contribution we present an overview of the most recent features and user interface of Gammapy along with example analyses using H.E.S.S, Fermi-LAT and simulated CTA data.

Speaker: Axel Donath
• 120
Identifying muon rings in VERITAS data using convolutional neural networks trained on Muon Hunters 2-classified images

Muons from extensive air showers appear as rings in images taken with Cherenkov telescopes, such as VERITAS. These muon ring images are used for the calibration of the VERITAS telescopes, however this calibration process can be improved with a more efficient muon-identification algorithm. Convolutional neural networks (CNNs) are used in many state-of-the-art image-recognition systems and are ideal for this purpose. However, by training a CNN on a dataset labelled by existing algorithms, the performance of the CNN would be limited by the suboptimal muon-identification efficiency of the original algorithms. Muon Hunters 2 is a citizen science project that asks users to label grids of VERITAS telescope images, stating which images contain muon rings. Each image is labelled 10 times by independent volunteers, and the votes are aggregated and used to assign a 'muon' or 'non-muon' label to the corresponding image. An analysis was performed using an expert-labelled dataset in order to determine the optimal vote fraction cut-offs for assigning labels to each image for CNN training. This was optimised so as to identify as many muon images as possible while avoiding false positives. The performance of this model will be presented and compared to existing muon identification algorithms employed in the VERITAS data analysis software. Using any extra images identified for calibration may require improvements to the light-distribution correction algorithm for muon rings with non-zero impact parameters.

Speaker: Mr Kevin Flanagan (University College Dublin)
• 121
Matched Runs Method to Study Extended Regions of Gamma-ray Emission

Imaging atmospheric Cherenkov telescopes, such as the Very Energetic Radiation Imaging Telescope Array System (VERITAS), are uniquely suited to resolve the detailed morphology of extended regions of gamma-ray emission. However, standard VERITAS data analysis techniques have insufficient sensitivity to gamma-ray sources spanning the VERITAS field of view (3.5°), due to difficulties with background estimation. For analysis of such spatially extended sources with 0.5° to greater than 2° radius, we developed the Matched Runs Method. This method derives background estimations for observations of extended sources using matched separate observations of known point sources taken under similar observing conditions. Our technique has been validated by application to archival VERITAS data. Here we present a summary of the Matched Runs Method and multiple validation studies on different gamma-ray sources using VERITAS data.

Speaker: Binita Hona (University of Utah)
• 122
New methods to reconstruct Xmax and the energy of gamma-ray air showers with high accuracy in large wide-field observatories

A new method to reconstruct the slant depth of the maximum of the longitudinal profile (XmaxXmax​) of high-energy showers initiated by gamma-rays as well as their energy (E0​) are presented. The method were developed for gamma rays with energies ranging from a few hundred GeV to around 10 TeV. An estimator of Xmax is obtained, event-by-event, from its correlation with the distribution of the particles' arrival time at the ground, or the signal at the ground for lower energies. An estimator of E0​ is obtained, event-by-event, using a parametrization that has as inputs the total measured energy at the ground, the amount of energy contained in a region near to the shower core and the estimated Xmax​. Resolutions about 40 (20) g/cm2 and about 30(20)% for, respectively, Xmax​ and E0​ at 1 (10) TeV energies are obtained, considering vertical showers. The obtained results are auspicious and can lead to the opening of new physics avenues for large wide field-of-view gamma-ray observatories. The dependence of the resolutions with experimental conditions is discussed.

Speaker: Ruben Conceição (LIP - Laboratório de Instrumentação e Física Experimental de Partículas)
• 123
Prototype Open Event Reconstruction Pipeline for the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) is the next-generation gamma-ray observatory
currently under construction.
It will improve over the current generation of imaging atmospheric Cherenkov telescopes (IACTs)
by at least one order of magnitude in sensitivity and be able to observe the whole
sky from a northern site in La Palma, Spain, and a southern one in Paranal, Chile.

CTA will also be the first open gamma-ray observatory.
Accordingly, the data analysis pipeline is developed as open-source software.
The event reconstruction pipeline accepts raw data of the telescopes and processes it to
produce suitable input for the higher-level science tools.
Its primary tasks include estimating the physical properties of each recorded
shower and providing the corresponding instrument response functions.

Ctapipe is a framework providing algorithms and tools to facilitate raw data calibration,
image extraction, image parameterization and event reconstruction.
Its main focus is currently the analysis of simulated data but it has also been successfully applied
for the analysis of data obtained with the first CTA prototype telescopes, such as the Large Size Telescope 1.

PyIRF is a library to calculate IACT instrument response functions,
needed to obtain physics results like spectra and light curves,
from the reconstructed event lists.

Building on these two, protopipe is a prototype for the event reconstruction pipeline for CTA.
Recent developments in these software packages will be presented.

Speaker: Maximilian Nöthe (TU Dortmund)
• 124
Reconstruction of extensive air shower images of the Large Size Telescope prototype of CTA using a novel likelihood technique

Ground-based gamma-ray astronomy requires reconstructing extensive air showers initiated by gamma rays impinging on the atmosphere. Imaging atmospheric Cherenkov telescopes collect the Cherenkov light induced by secondary charged particles in extensive air showers, creating an image of the shower in a camera. This image is parametrized and used to evaluate the type, energy and arrival direction of the primary particle that initiated the shower. This contribution shows the results of a novel reconstruction method based on likelihood maximization. The method is applied to observations of the Crab Nebula acquired with the Large Size Telescope prototype (LST-1) deployed at the Northern site of the Cherenkov Telescope Array. The novelty with respect to previous likelihood reconstruction methods lies in the definition of a likelihood per single camera pixel, accounting not only for the total measured charge, but also for its development over time. It considers the waveform acquired by each pixel involved in the reconstruction of the shower. This reconstruction, which considers also the response characteristics of the sensor in the camera pixel, leads to improved reconstruction of shower images and consequently allows for the recovery of the primary particles properties with an improved accuracy.

Speaker: Dr Gabriel Emery (University of Geneva - DPNC)
• 125
Reconstruction of stereoscopic CTA events using deep learning with CTLearn

The Cherenkov Telescope Array (CTA), conceived as an array of tens of imaging atmospheric
Cherenkov telescopes (IACTs), is an international project for a next-generation ground-based
gamma-ray observatory, aiming to improve on the sensitivity of current-generation instruments
by an order of magnitude and provide energy coverage from 20 GeV to more than 300 TeV.
Arrays of IACTs probe the very-high-energy gamma-ray sky. Their working
principle consists of the simultaneous observation of air showers initiated by
the interaction of very-high-energy gamma rays and cosmic rays with the atmosphere.
Cherenkov photons induced by a given shower are focused onto the camera plane
of the telescopes in the array, producing a multi-stereoscopic record of the event. This
image contains the longitudinal development of the air shower, together
with its spatial, temporal, and calorimetric information. The properties of
the originating very-high-energy particle (type, energy and incoming direction)
can be inferred from those images by reconstructing the full event using machine
learning techniques. In this contribution, we present a purely deep-learning
driven, full-event reconstruction of simulated, stereoscopic IACT events
and manipulating IACT data and for running deep learning models,
using pixel-wise camera data as input.

Speaker: Tjark Miener (IPARCOS, UCM)
• 126
Studies of Gamma Ray Shower Reconstruction Using Deep Learning

The ALTO project aims to build a particle detector array for very high energy gamma ray observations optimized for soft spectrum sources. The accurate reconstruction of gamma ray events, in particular their energies, using a surface array is an especially challenging problem at the low energies ALTO aims to optimize for. In this contribution, we leverage Convolutional Neural Networks (CNNs) to improve reconstruction performance at lower energies ( < 1 TeV ) as compared to the SEMLA analysis procedure, which is a more traditional method using mainly manually derived features.
We present performance figures using different network architectures and training settings, both in terms of accuracy and training time, as well as the impact of various data augmentation techniques.

Speaker: Tomas Bylund (Linnaeus University)
• 127
The identification of proton and gamma components in cosmic-rays based on deep learning algorithm

The Large High Altitude Air Shower Observatory (LHAASO), is a multi-component experiment located at Daocheng (4410 m a.s.l.), Sichuan province, P.R. China. The identification of gamma rays from protons is an important foundation and premise for gamma ray research. In this paper, we use deep learning algorithm to extract the key features of events directly based on a large amount of original information, and explore the identification power of gamma rays from protons of LHAASO experiment. The Convolutional Neural Network(CNN), Deep Neural Networks(DNN) and Graph Neural Networks (GNN) are trained and tested based on a large number of simulation events respectively. Compared with the traditional methods, we have found that the trained CNN, DNN and GNN models all have improvements in the effect of proton and gamma discrimination.

Speaker: F Zhang (Southwest Jiaotong University)
• 128
The use of convolutional neural networks for processing images from multiple IACTs in the TAIGA experiment

TAIGA experiment uses hybrid detection system for cosmic and gamma rays that currently includes three imaging atmospheric Cherenkov telescopes (IACTs). Previously we used convolutional neural networks to select gamma ray events and estimate the energy of the gamma rays based on an image from a single telescope. Subsequently we adapted these techniques to use data from multiple telescopes, increasing the quality of selection and the accuracy of estimates. All the results have been obtained with the simulated data of TAIGA Monte Carlo software.

Speaker: Stanislav Polyakov (SINP MSU)
• 129
Using Machine Learning for gamma/hadron separation with HAWC

Background showers triggered by hadrons represent over 99.9% of all particles arriving at ground-based gamma-ray observatories. An important stage in the data analysis of these observatories, therefore, is the removal of hadron-triggered showers from gamma showers. Currently, the High-Altitude Water Cherenkov (HAWC) gamma-ray observatory employs an algorithm that is a single cut in two variables, unlike other ground-based gamma-ray observatories (e.g. HESS, VERITAS) which employ a large number of variables to separate the primary particles. In this work, we explore machine learning techniques (Boosted Decision Trees and Neural Networks) to identify the primary particles that were detected by HAWC. Our new gamma/hadron separation techniques were tested on data from the Crab nebula, the standard reference in Very High Energy astronomy, showing an improvement compared to the standard HAWC background rejection method.

Speaker: Tomás Capistrán (Instituto de Astronomía, UNAM)
• 1:30 PM
Break
• Plenary: Review 01 01

#### 01

Convener: Jim Hinton (MPIK)
• 130
Constraining Magnetic Fields at Galactic Scales

Magnetic fields are ubiquitous in the Universe, from compact objects to cosmic scales, and they play a central role in a variety of astrophysical processes. Surprisingly, even the Galactic magnetic field (GMF) in our own Milky Way remains poorly understood because of the challenges of observing it and the complexity of the phenomena we use to study it. Though we still have too many models that might fit the data, this is not to say that the field has not developed in the last few years. Radio observations have been used since the 1970’s to study the GMF and remain one of the most useful tracers. More recently, surveys of polarized dust have given us a new observable that is complementary to the more traditional radio tracers. A variety of other new tracers and related measurements are becoming available to improve current understanding. In this talk, I will summarize: the tracers available; the models that have been studied; what has been learned so far; what the caveats and outstanding issues are; and one opinion of where the most promising future avenues of exploration lie.

Speaker: Tess Jaffe
• 131
Gamma-Ray Bursts detected at Very High Energies

Very high energy (VHE, >100 GeV) radiation from GRBs has eluded for several years all attempts of detection by Cherenkov telescopes, until the recent detection of strong VHE emission from the long GRB 190114C, located at redshift z=0.42.
The inclusion of TeV data in the modeling of afterglow multi-wavelength (from radio to X-rays) observations allows us to estimate physical properties that are usually unconstrained, such as the density of the external medium, the energy of the emitting particles, and the strength of the shock-amplified magnetic field. Since the first announcement of VHE detection from a GRB, three additional GRBs have been firmly detected by Cherenkov telescopes. In this talk I review the present status of observations and interpretation of VHE emission from GRBs. Prospects for future detections with the ASTRI-Mini Array and with CTA, revised in light of these recent observations, reveal that the VHE band is a very promising energy window for progressing our knowledge of GRB physics.

Speaker: Lara Nava
• 3:30 PM
Break
• Plenary: Highlight 02 01

#### 01

Convener: Stefan Funk (ECAP)
• 132
A tidal disruption event coincident with a high-energy neutrino

IceCube discovered a diffuse flux of high-energy neutrinos in 2013, and recently identified the flaring gamma-ray blazar TXS 0506+056 as a likely neutrino source. However, a combined analysis of the entire resolved gamma-ray blazar population limited the contribution of such objects to no more than 27% of the total neutrino flux, leaving the vast majority of the neutrino flux unexplained. Here we present the identification of a second probable neutrino source, the Tidal Disruption Event (TDE) AT2019dsg, found as part of a systematic search for optical counterparts to high-energy neutrinos using the Zwicky Transient Facility. The probability of finding such a TDE with our follow-up program by chance is just 0.2%. Multi-wavelength observations reveal the presence of a central engine powering particle acceleration in AT2019dsg, and confirm that this object can satisfy necessary conditions for PeV neutrino production.

Speaker: Robert Stein (Z_ICE (IceCube+NG))
• 133
Transition from Galactic to Extragalactic Cosmic Rays

Understanding the nature of the transition from Galactic to extragalactic cosmic rays (GCRs and EGCRs) has become a challenge in light of recent spectral and composition data. Galactic contributions appear to be disfavoured at energies beyond $10^{17} \, {\rm eV}$ where the composition becomes lighter, and extragalactic sources appear to inject mixed compositions, complicating the description of the EGCR contribution below ankle'' energies. As a result, the measured flux in the transition region cannot easily be accounted for. With the model-dependence of proposed extensions to both the Galactic and extragalactic contributions, a deeper understanding of CR propagation is in order, particularly within the Galactic magnetic field (GMF) as propagation herein shifts from diffusive to ballistic at these energies, which is expected to lead to a range of effects on CRs.

Using CRPropa3, we study these effects for rigidities between $10^{16-20} \, {\rm V}$. We identify various features at rigidities where the gyroradius equals typical length scales of the Galaxy, suggesting causes related to changes in the propagation regime. We further quantify modifications in the spectrum, composition and arrival direction of GCRs and EGCRs. We find that the GMF naturally induces a flux suppression of GCRs towards higher rigidities. This, in consequence, would lead to an increase in the mean mass of GCR primaries up to energies around the ankle'' in the cosmic ray spectrum. The distribution of GCR arrival directions is also shown to be correlated with the Galactic plane for rigidities above $10^{17}\, {\rm V}$. EGCRs experience no flux modification in the GMF if injected isotropically. Injection of pure dipoles, as well as single source scenarios indicate that the GMF isotropises injected anisotropies below $10^{18} \, {\rm V}$, but can still cause flux modifications depending on the direction of the anisotropy. Overall consequences to the transition of GCRs to EGCRs will be discussed.

Speaker: Alex Kääpä (Bergische Universität Wuppertal)
• 134
Physics of gamma-ray burst afterglow: implications of H.E.S.S. observations

Recently, the observational study of gamma-ray bursts (GRBs) in the very-high-energy (VHE) regime has quickly advanced with three successful detections. Currently, the list of published VHE GRBs contains GRB 180720B, GRB 190114C, and GRB 190829A. The fortunate proximity of the last event observed with H.E.S.S. (GRB 190829A occurred at z~0.08) allowed an unexpectedly long signal detection, up to 56 hours after the trigger, and accurate spectral determination in a broad energy interval, spanning between 0.18 and 3.3TeV. The obtained temporal and spectral properties of the VHE emission appeared to be remarkably similar to those seen in the X-ray band with Swift-XRT. However, in frameworks of the standard synchrotron-self-Compton (SSC) scenario such a coherent behavior is expected only during the early period of the afterglow phase, when the forward shock propagates with large bulk Lorentz factor, (\Gamma>100). SSC models are able to render VHE spectra compatible with the H.E.S.S. measurements only under extreme assumptions on the properties of the circumburst medium. We discuss the implications of the GRB 190829A detection for afterglow modeling and GRB physics.

Speaker: Dmitry Khangulyan (Rikkyo University)
• 5:30 PM
Break
• Discussion: 05 CR Mass composition | CRI 03

#### 03

• 135
Mass composition anisotropy with the TA SD data

Mass composition anisotropy is predicted by a number of theories describing sources of ultra-high-energy cosmic rays.
Event-by-event determination of a type of a primary cosmic-ray particle is impossible due to large shower-to-shower fluctuations, and the mass composition usually is obtained by averaging over some composition-sensitive observable determined independently for each extensive air shower (EAS) over a large number of events.
In the present study we propose to employ the observable $\xi$ used in the mass composition analysis of the Telescope Array surface detector (TA SD) data for the mass composition anisotropy analysis.
The $\xi$ variable is determined with the use of Boosted Decision Trees (BDT) technique trained with the Monte-Carlo sets, and the $\xi$ value is assigned for each event, where $\xi=1$ corresponds to an event initiated by the primary iron nuclei and $\xi=-1$ corresponds to a proton event.
Use of $\xi$ distributions obtained for the Monte-Carlo sets allows us to separate proton and iron candidate events from a data set with some given accuracy and study its distributions over the observed part of the sky.
Results for the TA SD 12-year data set mass composition anisotropy will be presented and possible applications for the cosmic-ray source models will be discussed. This presentation contains results we would like to include in a TA highlight talk.

Speaker: Yana Zhezher (ICRR, University of Tokyo & INR RAS, Moscow)
• 136
Cosmic-ray mass composition with the TA SD 12-year data

Telescope Array (TA) is the largest ultra-high-energy cosmic-ray (UHECR) observatory in the Northern Hemisphere. It is dedicated to detect extensive air showers (EAS) in hybrid mode, both by measuring the shower’s longitudinal profile with fluorescence telescopes and their particle footprint on the ground from the surface detector (SD) array. While fluorescence telescopes are can measure the most composition-sensitive characteristic of EAS, the depth of the shower maximum (Xmax), they also have the drawback of small duty cycle. This work aims to study the UHECR composition based solely on the surface detector data. For this task, a set of composition-sensitive observables obtained from the SD data is used in a machine-learning method – the Boosted Decision Tree. We will present the results of the UHECR mass composition based on the 12-year data from the TA SD using this technique, and we will discuss of the possible systematics imposed by the hadronic interaction models.

Speaker: Yana Zhezher (ICRR, University of Tokyo & INR RAS, Moscow)
• 137
The measurements of the cosmic ray energy spectrum and the depth of maximum shower development of Telescope Array Hybrid trigger events

The Telescope Array experiment is an ultra-high energy cosmic ray observatory located in Millard County, Utah, USA. The observatory consists of 3 fluorescence detector (FD) stations and 507 surface detectors (SD) that cover an area of ~700 km2. Hybrid trigger is an external trigger system for the SD arrays that prompts the SD to perform data acquisition when an FD detects a shower-like event. In comparison with the SD autonomous trigger, hybrid trigger allows the SD to collect the data of an air shower that has primary energy below 1018.5 eV, where the efficiency of SD autonomous trigger decreases rapidly. We present the measurements of the cosmic ray energy spectrum and the depth of maximum shower development of hybrid trigger events observed from October 2010 to June 2019.

Speaker: Mr Heungsu Shin (ICRR, University of Tokyo)
• 138
Combined fit of the energy spectrum and mass composition across the ankle with the data measured at the Pierre Auger Observatory

The combined fit of the energy spectrum and mass composition data above $5\cdot10^{18}\:\mathrm{eV}$ suggested the presence of extragalactic sources ejecting ultra-high-energy cosmic rays with relatively low maximum energies, hard spectral indices and mixed chemical compositions, dominated by the contribution of intermediate mass groups. Here we present an extension of the fit to lower energies, to include the feature observed near $5\cdot10^{18}\:\mathrm{eV}$ in the all-particle energy spectrum, the so-called ankle.
We show that it is possible to generate such a change of slope assuming that the flux below the ankle is provided by the superposition of some additional contributions. The simplest extension of this sort consists of introducing a supplemental extragalactic component at low energy, characterised by different physical parameters with respect to the one contributing above the ankle: such a component may originate from a different population of sources or be provided by interactions occurring in the acceleration sites. In this framework we also explore the possibility of including the end of a Galactic contribution at low energies.
The fit suggests that these scenarios provide a reasonable description of the measurements across the ankle, without affecting the results obtained for the above-ankle region.
In order to evaluate our capability to constrain the source models, we finally discuss the impact of the main experimental systematic uncertainties and of the theoretical models choice on the fit results.

Speaker: Eleonora Guido (Università degli Studi di Torino)
• 139
Results from the KASCADE-Grande data analysis

Speaker: Donghwa Kang (KIT)
• 140
New insights from old cosmic rays: A novel analysis of archival KASCADE data

Cosmic ray data collected by the KASCADE air shower experiment are competitive in terms of quality and statistics with those of modern observatories. We present a novel mass composition analysis based on archival data acquired from 1998 to 2013 provided by the KASCADE Cosmic ray Data Center (KCDC). The analysis is based on modern machine learning techniques trained on simulation data provided by KCDC. We present spectra for individual groups of primary nuclei, the results of a search for anisotropies in the event arrival directions taking mass composition into account, and search for gamma-ray candidates in the PeV energy domain

Speaker: Dmitriy Kostiunin (Z_HESS (High Energy Steroscopic System))
• 141
Cosmic Ray Composition between 2 PeV and 2 EeV measured by the TALE Fluorescence Detector

The Telescope Array (TA) cosmic rays detector located in the State of Utah in the United States is the largest ultra high energy cosmic rays detector in the northern hemisphere. The Telescope Array Low Energy Extension (TALE) fluorescence detector (FD) was added to TA in order to lower the detector's energy threshold, and has succeeded in measuring the cosmic rays energy spectrum down to PeV energies, by making use of the direct Cherenkov light produced by air showers. In this contribution we present the results of a measurement of the cosmic-ray composition using TALE FD data collected over a period of ~4 years. TALE FD data is used to measure the $X_{max}$ distributions of showers seen in the energy range of $10^{15.3}$ - $10^{18.3}$ eV. The data distributions are fit to Monte Carlo distributions of {H, He, N, Fe} cosmic-ray primaries for energies up to $10^{18}$ eV. Mean $X_{max}$ values are measured for the full energy range. TALE observes a light composition at the "Knee", that gets gradually heavier as energy increases toward the "Second-Knee". An increase in the $X_{max}$ elongation rate is observed at energies just above $10^{17.3}$ eV indicating a change in the cosmic rays composition from a heavier to a lighter mix of primaries.

Speaker: Tareq AbuZayyad (Loyola University Chicago; University of Utah)
• 142
Cosmic Ray Composition in the Second Knee Region as Measured by the TALE Hybrid Detector

The Telescope Array Low-energy Extension (TALE) experiment is a hybrid air shower detector for the observation of air showers induced by cosmic rays with energy above 10$^{16}$ eV. The TALE detector consists of a Fluorescence Detector (FD) station with 10 FD telescopes located at the TA Middle Drum FD Station (itself made up of 14 FD telescopes), and a Surface Detector (SD) array made up of 80 scintillation counters, including 40 with 400 m spacing and 40 with 600 m spacing. A triggering system for the TALE-SD using an external trigger from the TALE-FD, a so-called hybrid trigger, allows for a lower energy threshold. The TALE hybrid trigger system has been working since 2018. Here we present an estimate of the performance of hybrid detection using a Monte Carlo simulation, and a first measurement of the cosmic ray composition using the TALE-Hybrid detector.

Speaker: Keitaro Fujita (Graduate School of Science, Osaka City University)
• 143
Cosmic-Ray Studies with the Surface Instrumentation of IceCube

IceCube is a cubic-kilometer Cherenkov detector installed in deep ice at the geographic South Pole. IceCube's surface array, IceTop, measures the electromagnetic signal and mainly low-energy muons from extensive air showers above several 100 TeV primary energy, with shower bundles and high-energy muons detected by the in-ice detectors. In combination, IceCube and IceTop provide unique opportunities to study cosmic rays in detail with large statistics. This contribution summarizes recent results from these studies. In addition, the IceCube-Upgrade will include a considerable enhancement of the surface detector through the installation of scintillation detectors and radio antennas and possibly small air-Cherenkov telescopes. We will discuss the results of the prototype detectors installed at the South Pole and the prospects of this enhancement as well as the surface array planned for IceCube-Gen2.

Speaker: Andreas Haungs (Karlsruhe Institute of Technology - KIT)
• 144
HAWC measurements of the energy spectra of cosmic ray protons, helium and heavy nuclei in the TeV range

Current knowledge of the relative abundances and the energy spectra of the elemental mass groups of cosmic rays in the 10 TeV - 1 PeV interval are uncertain. This situation prevents carrying out precision tests that may lead to distinguish among the existing hypotheses on the origin and propagation of TeV cosmic rays in the galaxy. In order to learn more about the mass composition of these particles, we have employed HAWC data from hadron induced air showers in order to determine the spectra of three mass groups of cosmic rays: protons, helium and heavy nuclei with Z > 2. The energy spectra were estimated by using the Gold unfolding technique on the 2D distribution of the lateral shower age against the estimated primary energy of events with arrival zenith angles smaller than 45 degrees. The study was carried out based on simulations using the QGSJET-II-04 model. Results are presented for primary cosmic-ray energies from 8 TeV to 400 TeV. They reveal that the aforementioned cosmic ray spectra exhibit fine structures within the above primary energy range.

Speaker: Juan Carlos Arteaga Velazquez (Universidad Michoacana de San Nicolas de Hidalgo)
• 145
Indication of a mass-dependent anisotropy above $10^{18.7}\,$eV in the hybrid data of the Pierre Auger Observatory

We test the hypothesis of an anisotropy in the mass of cosmic-ray primaries as a function of galactic latitude. The mass estimate is made using the depth of shower maximum, $X_{\text{max}}$, from hybrid events measured at the Pierre Auger Observatory. The 14 years of available data are split into on- and off-plane regions using the galactic latitude of each event to form two distributions in $X_{\text{max}}$, which are compared using the Anderson-Darling 2-samples test. A scan over a subset of the data is used to select an optimal threshold energy of $10^{18.7}\,$eV and an angular split of the data into equally sized on- and off-plane subsamples. Applied to all events, the distribution from the on-plane region is found to have a mean $X_{\text{max}}$ which is $9.3 \pm 1.7^{+2.6}_{-2.2}\,\text{g}\,\text{cm}^{-2}$ shallower and a width which is $6.3\pm2.9^{+3.8}_{-2.8}\,\text{g}\,\text{cm}^{-2}$ narrower than that of the off-plane region. These differences are such as to indicate that the mean mass of the primary particles arriving from the on-plane region is higher than the mean mass of those coming from the off-plane region.
Monte-Carlo studies yield a preliminary $5.0^{+1.4}_{-1.5}\,\sigma$ post-trial statistical significance, where the uncertainties are of systematic origin. Penalizing for systematic uncertainties leads to an indication for anisotropy in mass composition above $10^{18.7}\,$eV at a preliminary confidence level of $3.5\,\sigma$. The anisotropy is observed independently at each of the four fluorescence telescope sites. Interpretations of possible causes of the observed effect will be discussed.

Speaker: Dr Eric Mayotte (Bergische Universtät Wuppertal)
• 146
Recent measurements of the cosmic ray energy spectrum and composition from the GRAPES-3 experiment

The GRAPES-3 experiment is located at Ooty in India. It consists of a densely packed array of 400 plastic scintillator detectors (1 $m^{2}$ area each) with 8 m inter-detector separation and a large area (560 $m^{2}$) muon telescope. It measures the cosmic rays from a few TeV to over 10 PeV, thereby providing a substantial overlap with direct experiments as well as covering the knee region. The shower parameters are reconstructed by fitting the observed particle densities with the NKG lateral distribution function. The relation between the shower size and energy of primary cosmic rays is derived by using simulations with the SIBYLL-2.3c and QGSJET-II-04 hadronic interaction models. The Bayesian unfolding method is used for obtaining the energy spectrum. Measurements of nuclear composition are obtained by comparing muon multiplicity distributions (MMDs) for proton, helium, nitrogen, aluminium, and iron primaries obtained from the simulations against the MMDs measured by the muon telescope. The details of the analysis method and the extracted energy spectrum and composition from a few TeV to 10 PeV will be presented.

Speaker: Mr Fahim Varsi (Indian Institute of Technology, Kanpur)
• 147
Results on mass composition of cosmic rays as measured with LOFAR

We present an updated analysis of the mass composition of cosmic rays in the $10^{17}$ to $10^{18}$ eV energy range. It is based on measurements with the LOFAR telescope of the depth of shower maximum, $X_{\mathrm{max}}$.
We review the improvements to the simulation-based reconstruction setup, as well as the selection method to obtain a minimally biased $X_\mathrm{max}$-dataset. Systematic uncertainties on $X_\mathrm{max}$ have been lowered to an estimated 7 to 9 $\mathrm{g/cm^2}$, at a resolution of about 20 $\mathrm{g/cm^2}$ per shower.
Results include estimates of the mean and standard deviation of the $X_\mathrm{max}$-distribution. A statistical analysis at distribution level has been done as well, using a 4-component model of light to heavy nuclei.
It confirms our previous results showing a significant low-mass fraction in this energy range.
We discuss consistency with existing results on Xmax and mass composition.

Speaker: Arthur Corstanje (Free University Brussels)
• 148
Telescope Array Combined Fit to Cosmic Ray Spectrum and Composition

The cosmic rays observed at Earth have propagated through the universe over cosmological distances. The propagation should effect both the observed spectrum of cosmic rays and the abundance of different nuclear species that are observed at each energy. By performing a combined fit of Telescope Array spectrum and composition measurements to a simple source model consisting of a universal power-law with a rigidity dependent cutoff and variable, five-component composition fractions, one can constrain the possible sources of cosmic rays. We will present the results of such a fit using the Telescope Array surface array spectral measurements and the Telescope Array hybrid and stereo composition measurements.

Speaker: Douglas Bergman (University of Utah)
• 149
The depth of the shower maximum of air showers measured with AERA

The Auger Engineering Radio Array (AERA) is currently the largest array of radio antennas for the detection of cosmic rays, spanning an area of $17$ km$^2$ with 153 radio antennas, measuring in the energy range around the transition from galactic to extra-galactic origin. It measures the radio emission of extensive air showers produced by cosmic rays, in the $30-80$ MHz band. The cosmic-ray mass composition is a crucial piece of information in determining the sources of cosmic rays and their acceleration mechanisms. The composition can be determined with a likelihood analysis that compares the measured radio-emission footprint on the ground to an ensemble of footprints from CORSIKA/CoREAS Monte-Carlo air shower simulations. These simulations are also used to determine the resolution of the method and to validate the reconstruction by identifying and correcting for systematics. We will present the method for the reconstruction of the depth of the shower maximum, compare our results to the independent fluorescence detector reconstruction measured on an event-by-event basis, and show the results of the cosmic-ray mass composition reconstruction with AERA in the energy range from $10^{17.5}$ to $10^{19}$ eV for data taken over the past seven years.

Speaker: Bjarni Pont
• Discussion: 08 Radio Observations of Cosmic Rays | CRI-NU 06

#### 06

• 150
Self-trigger radio prototype array for GRAND

The GRANDProto300 (GP300) array is a pathfinder of the Giant Radio Array for Neutrino Detection (GRAND) project. The deployment of the array, consisting of 300 antennas, will start in 2021 in a radio-quiet area of ~200km^2 near Lenghu (~3000 m a.s.l.) in China.

Serving as a test bench, the GP300 array is expected to realise techniques of autonomous radio detection such as identification and reconstruction of nearly horizontal cosmic-ray (CR) air showers. In addition, the GP300 array is at a privileged position to study the transition between Galactic and extragalactic origins of cosmic rays, due to the large effective area and the precise measurements of both energy and mass composition for CRs with energies ranging from 30 PeV to 1 EeV. Using the GP300 array we will also investigate the potential sensitivity for radio transients such as Giant Radio Pulses and Fast Radio Bursts at 100-200 MHz range.

Speaker: Dr Yi Zhang (Purple Mountain Observatory, Chinese Academy of Sciences)
• 151
Modeling and Validating RF-Only Interferometric Triggering with Cosmic Rays for BEACON

The Beamforming Elevated Array for COsmic Neutrinos (BEACON) is a novel detector concept that utilizes a radio interferometer atop a mountain to search for the radio emission from extensive air showers created by Earth-skimming tau neutrinos. The prototype, located at the White Mountain Research Station in California, consists of 4 crossed-dipole antennas operating in the 30-80 MHz range and uses a directional interferometric trigger for reduced thresholds and background rejection. The prototype will first be used to detect down-going cosmic rays to validate the detector model. Here, we present the methodology and results of a Monte-Carlo simulation developed to predict the acceptance of the prototype to cosmic rays. In this simulation, cosmic ray induced air showers are generated in an area around the prototype array. It is then determined if a given shower triggers the array using radio emission simulations from ZHAireS and antenna modelling from XFdtd. The time-domain waveforms, event rates, and angular distributions predicted by this simulation can then be compared with experimental data to validate the detector model.

Speaker: Andrew Zeolla (Pennsylvania State University)
• 152
TAROGE-M: Radio Observatory on Antarctic High Mountain for Detecting Near-Horizon Ultra-High Energy Air Showers

The TAROGE-M observatory is an autonomous antenna array on the top of Mt.~Melbourne ($\sim2700$ m altitude) in Antarctica, designed to detect radio pulses from ultra-high energy (over $10^{17}$ eV) air showers coming from near-horizon directions. The targeted sources include cosmic rays, Earth-skimming tau neutrinos, and most of all, the anomalous near-horizon upward-going events of yet unknown origin discovered by ANITA experiments. The detection concept follows that of ANITA: monitoring large area of ice from high-altitude and taking advantage of strong geomagnetic field and quiet radio background in Antarctica, whereas having significantly greater livetime and scalability.

The TAROGE-M station, upgraded from its prototype built in 2019, was deployed in January 2020, and consists of 6 log-periodic dipole antennas pointing horizontally with bandwidth of 180-450 MHz. The station is then calibrated with drone-borne transmitter, with which the event reconstruction obtained $\sim0.3^\circ$ angular resolution. The station was then smoothly operating in the following month, with the live time of $\sim30$ days, before interrupted by a power problem, and its online filtering has identified several candidate cosmic-ray events and sent out via satellite communication. In this paper, the instrumentation of the station for polar and high-altitude environment, its radio-locating performance, the preliminary result on cosmic-ray detection, and the future extension plan are presented.

Speaker: Shih-Hao Wang (National Taiwan University)
• 153
The NuMoon Experiment: Lunar Detection of Cosmic Rays and Neutrinos with LOFAR

The low flux of ultra-high-energy cosmic rays (UHECRs) makes it challenging to understand their origin and nature. A very large effective aperture is provided by the lunar Askaryan technique. Particle cascades in a dielectric medium produce radio emission through the Askaryan effect. Ground based radio telescopes are used to search for nanosecond radio pulses that are produced when cosmic rays or neutrinos interact with the Moon’s surface. The LOw Frequency ARray (LOFAR) is currently the largest radio array operating at frequencies between $110 - 190$~MHz; the optimum frequency range for lunar signal search and $30 - 80$~MHz for radio detection of air showers. One minute of observation has been carried out with six LOFAR stations beam-formed towards the Moon. In this contribution, we present some preliminary results of the analysis of the data and a complete description of the analysis steps.

Speaker: Godwin Komla Krampah (Vrije University of Brussels)
• 154
Radio-Morphing: a fast, efficient and accurate tool to compute the radio signals from air-showers

The preparation of next generation large-scale radio detectors such as GRAND requires to run massive air-shower simulations to evaluate the radio signal at each antenna position. Radio-Morphing was developed for this purpose. It is a semi-analytical tool that enables a fast computation of the radio signal emitted by any air-shower at any location, from the simulation data of one single reference shower at given positions. Radio-Morphing was demonstrated to generate the electric field time traces with amplitudes in good agreement (<30% difference for two thirds of signals) with microscopic simulations, while reducing the computation time by several orders of magnitude. However, several features still needed to be addressed for the tool to be fully efficient and accurate. We present here major improvements on the Radio-Morphing method that have been implemented recently. The upgraded version is based on revised and refined scaling laws, derived from physical principles. It also includes a new spatial interpolation technique, thanks to which an excellent signal timing accuracy can be reached. We will present the methodology, performances and possible applications of this universal tool.

Speaker: Simon Chiche (Institut d'Astrophysique de Paris)
• 155
The Zettavolt Askaryan Polarimeter (ZAP) mission concept: radio detection of ultra-high energy cosmic rays in low lunar orbit.

Probing the ultra-high energy cosmic ray (UHECR) spectrum beyond the cutoff at ~40 EeV requires an observatory with an acceptance that is impractical to achieve with ground arrays. We present a concept, designated the Zettavolt Askaryan Polarimeter (ZAP), for radio detection of UHECRs impacting the Moon’s regolith from low-lunar orbit. ZAP would observe several thousands of events above the cutoff (~40 EeV) with a full-sky field of view to test whether UHECRs originate from Starburst Galaxies, Active Galactic Nuclei, or other sources associated with the matter distribution of the local universe at a distance > 1 MPc. The unprecedented sensitivity of ZAP to energies beyond 100 EeV would enable a test of source acceleration mechanisms. At higher energies, ZAP would produce the most stringent limits on super heavy dark matter (SHDM) via limits on neutrinos and gamma rays resulting from self-annihilation or decay.

Speaker: Andres Romero-Wolf (Jet Propulsion Laboratory, California Institute of Technology)
• 156
Reconstructing inclined extensive air showers from radio measurements

We present a reconstruction algorithm for extensive air showers with zenith angles between 65° and 85° measured with radio antennas in the 30-80 MHz band. Our algorithm is based on a signal model derived from CoREAS simulations which explicitly takes into account the asymmetries introduced by the superposition of charge-excess and geomagnetic radiation as well as by early-late effects. We exploit correlations among fit parameters to reduce the dimensionality and thus ensure stability of the fit procedure. Our approach reaches a reconstruction efficiency near 100% with an intrinsic resolution for the reconstruction of the electromagnetic energy of well below 5%. It can be employed in upcoming large-scale radio detection arrays using the 30-80 MHz band, in particular the AugerPrime Radio detector of the Pierre Auger Observatory, and can likely be adapted to experiments such as GRAND operating at higher frequencies.

Speaker: Tim Huege (Karlsruhe Institute of Technology and Vrije Universiteit Brussel)
• 157
Classification and Denoising of Cosmic-Ray Radio Signals using Deep Learning

Speaker: Abdul Rehman (University of Delaware)
• 158
Cross-calibrating the energy scales of cosmic-ray experiments using a portable radio array

Different experiments use different techniques to detect and reconstruct cosmic-ray events, yielding different energy scales. Having a method to compare the energy scales of different experiments with minimal uncertainty is necessary in order to make meaningful comparisons of their spectra and composition measurements, which are used to create global models of cosmic-ray sources, acceleration and propagation. Comparing energy scales has proven to be difficult, given that uncertainties on energy measurements depend on the location, technique and equipment used. In this contribution we introduce a new radio-based technique which will be used to build a universal cosmic-ray energy scale. Radio detection provides a measure of the radiation energy in air showers, which scales quadratically with the electromagnetic energy. Once the local magnetic field strength is taken into account, radiation energy can be directly compared at different locations. A portable array of antennas will be built and deployed at various experiments, measuring radiation energy in conjunction with the host experiment’s traditional air shower measurements. The energy measured at each location can then be directly compared via the contemporaneous radiation energy measurements. Using radiation energy to compare the energy scales eliminates uncertainties due to measurements being made at different locations, and using the same array at each site eliminates the uncertainties associated with the equipment and calibration. This will allow for a cross-calibration of the energy scales of different experiments with minimal uncertainty. Here we present the technique and report on the status of a prototype array that began taking data in January 2021.

Speaker: Katharine Mulrey (Vrije Universiteit Brussel)
• 159
Expected performance of interferometric air-shower measurements with radio antennas

Interferometric measurements of the radio emission of extensive air showers allow reconstructing cosmic-ray properties. A recent simulation study with an idealised detector promised measurements of the depth of the shower maximum $X_\mathrm{max}$ with an accuracy better than 10$\,$g$\,$cm$^{-2}$.
In this contribution, we evaluate the potential of interferometric $X_\mathrm{max}$ measurements of (simulated) inclined air showers with realistically dimensioned, sparse antenna arrays. We account for imperfect time synchronisation between individual antennas and study its inter-dependency with the antenna density in detail. We find a strong correlation between the antenna multiplicity (per event) and the maximum acceptable inaccuracy in the time synchronisation of individual antennas. From this result, prerequisites for the design of antenna arrays for the application of interferometric measurements can be concluded. For data recorded with a time synchronisation accurate to 1$\,$ns within the commonly used frequency band of 30 to 80$\,$MHz, an antenna multiplicity of $\geq 50$ is needed to achieve an $X_\mathrm{max}$ reconstruction with an accuracy of 20$\,$g$\,$cm$^{-2}$. This multiplicity is achieved measuring inclined air showers with zenith angles $\theta \geq 77.5^\circ$ with 1$\,$km spaced antenna arrays, while vertical air showers with zenith angles $\theta \leq 40^\circ$ require an antenna spacing below 100$\,$m. Furthermore, we find no improvement in $X_\mathrm{max}$ resolution applying the interferometric reconstruction to measurements at higher frequencies, i.e., up to several hundred MHz.

Speaker: Felix Schlüter (Karlsruhe Institute of Technology - Institute for Astroparticle Physics)
• 160
First results from the AugerPrime Radio Detector

The Pierre Auger Observatory investigates the properties of the highest-energy cosmic rays with unprecedented precision. The aim of the AugerPrime upgrade is to improve the sensitivity to the primary particle type. The improved mass sensitivity is the key to exploring the origin of the highest-energy particles in the Universe. The purpose of the Radio Detector (as part of AugerPrime) is to extend the sensitivity of the mass measurements to zenith angles above 60°. A radio antenna, sensitive in two polarization directions and covering a bandwidth from 30 to 80 MHz, will be added to each of the 1661 surface detector stations over the full 3000 km2 area, forming the world’s largest radio array for the detection of cosmic particles. Since November 2018, an engineering array
comprised of ten stations has been installed in the field.
The radio antennas are calibrated using the Galactic (diffuse) emission. The sidereal modulation of this signal is monitored continuously and is used to obtain an end-to-end calibration from the receiving antenna to the ADC in the read-out electronics. The calibration method and first results will be presented.
The engineering array is also fully integrated in the data acquisition of the Observatory and records air showers regularly. The first air showers detected simultaneously with the water-Cherenkov detectors and the Radio Detectors will be presented. Simulations of the detected showers, based on the reconstructed quantities, have been conducted with CORSIKA/CoREAS. A comparison of the measured radio signals with those predicted by simulations exhibits satisfying agreement.

• 161
Performance of SKA as an air shower observatory

The low frequency segment of SKA in Australia will have an extremely dense antenna array spanning an area of roughly 0.5 km$^2$. It offers unique possibilities for high-resolution observations of air showers. Compared to LOFAR, it will have a much more homogeneous ground coverage, an increased frequency bandwidth (50-350 MHz), and the possibility to continuously observe with nearly 100% duty cycle.

SKA will observe air showers in the range 10$^{16}$ eV - 10$^{18}$ eV with a reconstruction resolution on Xmax of around 10 g/cm$^2$. This allows for a high-precision study of mass composition in the energy regime where a transition is expected from Galactic to extragalactic origin. In addition, SKA will be able to put constraints on hadronic interaction models, which is crucial for interpreting the data in this complex energy range.

In this talk, we will show the results of a full detector simulation and demonstrate the capabilities of SKA, including energy and Xmax reconstruction, as well as more advanced methods to constrain the shape of the longitudinal development of air showers.

Speaker: Stijn Buitink (Vrije Universiteit Brussel (VUB))
• 162
Simulation and Optimisation for the Radar Echo Telescope for Cosmic Rays

The Radar Echo Telescope for Cosmic Rays (RET-CR) will use the radar echo technique to detect the in-ice continuation of an ultra high energy cosmic ray (UHECR) air shower. When a UHECR particle cascade propagates into a high-elevation ice sheet, it produces a dense in-ice cascade of charged particles which can reflect incoming radio waves. Through the detection of transmitted radio waves, the energy and direction of the UHECR can be reconstructed. RET-CR will consist of a transmitter array, receiver antennas and a surface scintillator plate array.

In this poster we present the simulation efforts for RET-CR performed to optimise the surface array layout and triggering system, which finally leads to the prediction of the expected event rate. Showers are generated using the CORSIKA Monte Carlo code. The energy deposits in the scintillators are then found by propagating the particle output from CORSIKA through the scintillating material in Geant4. Thresholds are applied to the energy deposits to determine which showers trigger providing the surface detector efficiency. Additionally, CoREAS is used to generate radio emission which will be used to reconstruct events with the surface array. For the prediction of the event rate seen by the in-ice radar system, we use a simulation chain of existing and new tools. UHECR showers are generated using the CORSIKA Monte Carlo code, which are then propagated through a realistic ice layer using Geant4. The energy depositions from the Geant4 simulations were subsequently used in RadioScatter to calculate the radar scatter amplitude to trigger the in-ice system leading to a prediction of the expected event rates for the RET-CR detector.

Speaker: Rose Stanley (IIHE - VUB)
• 163
Simulation Study of the Observed Radio Emission of Air Showers by the IceTop Surface Extension

Multi-detector observations of individual air showers are critical to make significant progress to precisely determine cosmic-ray quantities such as mass and energy of individual events and thus bring us a step forward in answering the open questions in cosmic-ray physics. An enhancement of IceTop, the surface array of the IceCube Neutrino Observatory, is currently underway and includes adding antennas and scintillators to the existing array of ice-Cherenkov tanks. The radio component will improve the characterization of the primary particles by providing an estimation of Xmax and a direct sampling of the electromagnetic cascade, both important for per-event mass classification. A prototype station has been operated at the South Pole and has observed showers, simultaneously, with the three detectors types. The observed radio signals of these events are unique as they are measured in the 100-350 MHz band, higher than many other cosmic-ray experiments. We present a comparison of the detected events with the waveforms from CoREAS simulations, convoluted with the end-to-end electronics response, as a verification of the analysis chain. Using the detector response and the measurements of the prototype station as input, we update a Monte-Carlo-based study on the potential of the enhanced surface array for the hybrid detection of air showers by scintillators and radio antennas.

Speaker: Alan Coleman (University of Delaware)
• 164
Simulations of radio emission from air showers with CORSIKA 8

CORSIKA 8 is a new framework for air shower simulations implemented in modern C++17, based on past experience with existing codes like CORSIKA 7. The flexibility of this framework allows for the inclusion of radio-emission calculations as an integral part of the program. Our design makes radio simulations general and gives the user the freedom to choose between different formalisms, such as the “Endpoints” and “ZHS” formalisms. In addition, it takes advantage of the flexibility of the CORSIKA 8 environment and geometry design, allowing future updates to more complex scenarios such as showers crossing from air into dense media. Our first results, along with comparisons with other simulation programs like CoREAS in CORSIKA 7 and ZHAireS are going to be presented. In the future, based on our design, the opportunity arises for radio simulations to achieve a significant boost in performance by deploying parallel computing techniques, in particular employing GPUs, and hence, perform more sophisticated radio-emission studies.

Speaker: Nikolaos Karastathis (Institute for Astroparticle Physics, Karlsruhe Institute of Technology)
• 165
TAROGE experiment and reconstruction technique for near-horizon impulsive radio signals induced by Ultra-high energy cosmic rays

Taiwan Astroparticle Radiowave Observatory for Geo-synchrotron Emissions (TAROGE) is antenna arrays sitting on high coastal mountains of Taiwan, pointing to the Pacific Ocean for the detection of near-horizon extensive air showers (EAS) induced by ultra-high energy cosmic rays and Earth-skimming tau neutrinos. TAROGE would improve the detection capability by collecting both the direct-emissions and the ocean-reflected signal on a vast area of ocean which is visible from Taiwan’s high mountains. Four TAROGE stations in Taiwan have been deployed in the past few years. Except for the first station, which is a prototype station for the purposes of radio survey and optimization of instrument parameters, other three stations are still operating.
We develop a new angular reconstruction method based on a deconvolution of radio reflection on the ground which is an important systematic effect for the near-horizon events. The response of the ground reflection is measured with a drone-borne calibration pulser. We achieved a sub-degree angular resolution for near horizon event. In this paper, we discuss details of the method and the results. A brief status report of the TAROGE project will also be reported.

Speaker: Mr Yaocheng Chen (Dept. of Physics, Grad. Inst. of Physics & Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, Taipei, Taiwan)
• Discussion: 33 Photodetection in Cherenkov Detectors | NU 05

#### 05

• 166
The Wavelength-shifting Optical Module (WOM) for the IceCube Upgrade

The Wavelength-shifting Optical Module, or WOM, is a novel optical sensor that uses wavelength shifting and light guiding to substantially enhance the photosensitive area of UV optical modules. It has been designed for the IceCube Upgrade, a seven-string extension of the IceCube detector planned for the 2023/2024 South Pole deployment season, but its design can be applied to any large particle detector based on the detection of Cherenkov light. The WOM consists of a hollow quartz cylinder (detection area) coated in wavelength shifting paint with two PMTs attached to the end faces of the cylinder. The light-collecting quartz increases the effective photocathode area of the light sensors without producing additional dark current, making it suitable for low-signal, low-noise applications. For larger event distances where UV absorption shifts the spectrum to longer wavelengths, the design can be augmented with PMTs. We will report on the design and performance of the WOM with a focus on the 12 modules in production for deployment in the IceCube Upgrade.

Speaker: John Rack-Helleis (JGU Mainz)
• 167
Performance studies for a next-generation optical sensor for IceCube-Gen2

We present performance studies of a segmented optical module for the IceCube-Gen2 detector. Based on the experience gained in sensor development for the IceCube Upgrade, the new sensor will consist of up to 18 4-inch PMTs housed in a transparent pressure vessel, providing homogeneous 4 pi coverage. The use of custom moulded optical gel 'pads' around the PMTs enhances the photon capture rate via total internal reflection at the gel-air interface. The contribution presents simulation studies of various sensor, PMT, and gel pad geometries aimed at optimizing the sensitivity of the optical module in the face of confined space and harsh environmental conditions.

Speaker: Dr Nobuhiro Shimizu (Chiba Univeristy)
• 168
Performance of the D-Egg optical sensor for the IceCube-Upgrade

New optical sensors called the "D-Egg" have been developed for cost-effective instrumentation for the IceCube Upgrade. With two 8-inch high QE photomultipliers, they offer increased effective photocathode area while retaining as much of the successful IceCube Digital Optical Module (DOM) design as possible. Mass production of D-Eggs has started in 2020. By the end of 2021, there will be 310 D-Eggs produced with 288 deployed in the IceCube Upgrade. The D-Egg readout system uses advanced technologies in electronics and computing power. Each of the two PMT signals is digitized using ultra-low-power 14-bit ADCs with a sampling frequency of 250-MSPS, enabling seamless and lossless event recording from single-photon signals to signals exceeding 200pe within 10ns, as well as flexible event triggering. In this paper, we report the single photon detection performance as well as the multiple photon recording capability of D-Eggs from the mass production line which have been evaluated with the built-in DAQ system.

Speaker: Colton Hill (ICEHAP, Chbia University)
• 169
Design of an Efficient, High-Throughput Photomultiplier Tube Testing Facility for the IceCube Upgrade

The IceCube Upgrade is an extension of the IceCube detector at the geographic South Pole. It consists of seven new strings with novel instrumentation. More than 430 multi-PMT optical modules called "mDOMs", housing 24 3-inch PMTs each, will be produced for the Upgrade. This will require testing and pre-calibration on a short timescale of more than 10,000 PMTs prior to assembly and deployment. We present the design of a PMT testing facility that enables simultaneous testing of roughly 100 PMTs per day at temperatures down to -20°C. The design is implemented at RWTH Aachen University and TU Dortmund University in parallel to achieve a throughput of up to 1,000 PMTs per week. This will enable a steady supply of tested PMTs to the production sites, which is critical for the Upgrade, as well as the future IceCube-Gen2 project.

Speaker: Lasse Halve (RWTH Aachen University)
• 170
Evaluation of large area photomultipliers for use in a new Baksan Large Neutrino Telescope project

We present results of advance studies of large area photomultipliers (PMTs) of different types from several manufacturers for use in a new Baksan Large Neutrino telescope. At first, requirements for photodetectors to be used in the telescope were formulated. Parameters of 8-inch, 10-inch and 20-inch PMTs were thoroughly studied. 8-inch PMTs under studies were ET9350 from ET Enterprises, R5912 and R5912-100 from Hamamatsu Photonics. 10-inch PMTs – R7081 and R7081-100 and R7081-100-WA from Hamamatsu Photonics. 20-inch PMTs – R12860 from Hamamatsu Photonics and MCP-PMT from NNVT. Particular emphasis was done on measurements of photocathode sensitivity, single photoelectron response, TTS, dark current counting rate and afterpulses rate.

Speaker: Mr Nikita Ushakov (Institute for Nuclear Research of the Russian Academy of Science, Prospekt 60-letiya Oktyabrya 7a, Moscow 117312, Russia)
• 171
Large area photodetectors in photon detection for large-scale neutrino physics experiments: single large area PMTs and multi small PMTs approaches.

More than 40 years ago beginning of works on deep underwater high energy neutrino telescope projects (DUMAND and Baikal) inspired development of new photon detectors: large area photomultipliers (PMTs), multi small PMT optical modules, small PMTs equipped with wavelength shifting plates and rods and even small area solid state photon detectors for such kind application. Now days we witness rebirth of the multi small PMT approach and it started to compete quite successfully with a single large area photon detector approach. The latter have been reigning supreme for almost half century. But recent developments of astroparticle physics experiments demonstrated good competiveness of the “multi small PMTs” idea. Several projects of astroparticle physics experiments may serve as good examples, Km3NET project and coming JUNO experiment among them. We present pros and cons of both approaches.

Speaker: Sultim Lubsandorzhiev (Institute for Nuclear Research of the Russian Academy of Sciences)
• 172
Enhanced photon detection efficiency for next-generation neutrino telescopes using photon traps

We propose a photon trap designed for improved photon detection efficiency in a cost-efficient way. Wavelength Shifting plastic sheets (WLS) are deployed at the bottom of a PMT, surrounded by dichroic film by which photons are efficiently trapped and guided to the PMT. We measured wave-length dependent transmittance of a commercially available dichroic film in water, a key variable determining photon trapping efficiency. We ran a Geant4 based simulation with the property of the commercially available dichroic film as a realistic case. We also ran a simulation with a hypothetical dichroic film whose bandpass is optimized to absorption and reemission spectra of the WLS and the quantum efficiency of the PMT, as an ideal case. The preliminary results of the photon collection and detection efficiency enhancements are computed, as well as timing distribution of the photons. We discuss how this new conceptual design can be applied to next-generation neutrino telescopes.

Speaker: Koun Choi (SKKU)
• 173
A next-generation optical sensor for IceCube-Gen2

For the in-ice component of the next generation neutrino observatory at the South Pole, IceCube-Gen2, a new sensor module is being developed, which is an evolution of the DEgg and mDOM sensors developed for the IceCube Upgrade. The sensor design features up to 18 4-inch PMTs distributed homogeneously in a borosilicate glass pressure vessel. Challenges arise for the mechanical design from the tight constraints on the bore hole diameter (which will be 2 inches smaller than for IceCube Upgrade) and from the close packing of the PMTs. The electronics design must meet the space constraints posed by the mechanical design as well as the power consumption and cost considerations from over 10,000 optical modules being deployed. This contribution presents forward-looking solutions to these design considerations. Prototype modules will be installed and integrated in the IceCube Upgrade.

• 174
Data Quality Monitoring system of the Baikal-GVD experiment

The main purpose of the Baikal-GVD Data Quality Monitoring (DQM) system is to monitor the status of the detector and collected data. The system estimates quality of the recorded signals and performs the data validation. The DQM system is integrated with the Baikal-GVD’s unified software framework (“BARS”) and operates in quasi-online manner. This allows us to react promptly and effectively to the changes in the telescope conditions.

Speaker: Maksim Sorokovikov (JINR)
• 175
Design and performance of the multi-PMT optical module for IceCube Upgrade

The IceCube Upgrade is the first step towards the next-generation neutrino observatory at the South Pole, IceCube-Gen2, and will be installed in the central region of the existing array. The Upgrade will consist of 693 newly developed, densely spaced optical sensors and 50 standalone calibration devices, which will enhance IceCube's capabilities both at low and high neutrino energies. 402 of the new sensors will be multi-PMT Digital Optical Modules (mDOMs). Consisting of 24 small photomultipliers arranged inside a pressure vessel, the mDOM features a large sensitive area distributed nearly homogeneously over the full solid angle. The use of multiple, individually read-out PMTs allows directional information to be obtained for the registered photons and enables the use of multiplicity triggering within a single module, e.g., for background suppression. The challenges driving the mDOM development included tight restrictions on module size, data-transfer rate, and power consumption as well as the harsh environment in the deep ice at the South Pole. In this contribution we present the final mDOM design that meets these challenges.

Speaker: Lew Classen (Westfälische Wilhelms-Universität Münster)
• 176
Experimental string with fiber optic data acquisition for Baikal-GVD

The first stage of the construction of the deep underwater neutrino telescope Baikal-GVD is planned to be completed in 2024. The second stage of the detector deployment is planned to be carried out using a data acquisition system based on fiber optic technologies, which will allow for an increased data throughput and looser, more flexible trigger conditions, thus maximizing the neutrino detection efficiency. A dedicated experimental string has been built and deployed at the Baikal-GVD site to test the new technological solutions. We present the principle of operation and the results of in-situ tests of the experimental string.

• 177
Exploring a PMT+SiPM hybrid optical module for next generation neutrino telescopes

Cosmic neutrinos are unique probes of the high energy universe. IceCube has discovered a diffuse astrophysical neutrino flux since 2013, but their origin remains elusive. The potential sources could include, for example, active galactic nuclei, gamma-ray bursts and star burst galaxies. To resolve those scenarios, higher statistics and better angular resolution of astrophysical neutrinos are needed. An optical module with larger photon collection area and more precise timing resolution in a next generation neutrino telescope could help. Silicon photon multipliers (SiPMs), with high quantum efficiency and fast responding time, combining with traditional PMTs, could boost photon detection efficiency and pointing capability. We will present a study on exploring the benefits of combining multiple PMTs and SiPMs in an optical module.

Speaker: Fan Hu (Peking University)
• 178
Light concentrators for large-volume detector at the Baksan Neutrino Observatory

At the Baksan Neutrino Observatory deployed in the Caucasus mountains, it is proposed to create, at a depth corresponding to about 4700 mwe, a large-volume neutrino detector based on a liquid scintillator with a target mass of 10 kt. The main physics goals of the detector are low-energy neutrino physics, astrophysics and geophysics.
The highest possible light yield is crucial for such detectors. To improve light yield and energy resolution in large-volume neutrino detectors, light concentrators are often mounted on photomultiplier tubes to increase the detection efficiency of optical photons from scintillation or Cherenkov light induced by charged particles. We present the results of recent R&D work aimed to develop light concentrators for the Baksan large-volume liquid scintillation neutrino detector.

Speaker: Mr Almaz Fazliakhmetov (Institute for Nuclear Research of the Russian Academy of Science, Prospekt 60-letiya Oktyabrya 7a, Moscow 117312, Russia)
• 179
P-ONE second pathfinder mission: STRAW-b

P-ONE (Pacific Ocean Neutrino Explorer) collaboration was born with the aim of building a new large-scale neutrino telescope in the Pacific Ocean, at 2600 m b.s.l. in Cascadia Basin, off Vancouver Island.
The first steps aimed at the feasibility study and the characterization of the optical properties of the site with a first pathfinder project named STRAW (STRing for Absorption length in Water), deployed in 2018.
During the last two years a second pathfinder project has been developed: STRAW-b.
The main goal of STRAW-b is to validate the attenuation length already measured by STRAW and to add new information on the background characterization with the study of the deep sea diffused light spectrum. It consists of a 500 m mooring (electrical-optical cable communication) equipped with three Standard Modules for environmental monitoring and seven Specialised Modules for background analysis and attenuation length measurements. All the modules are hosted in spherical 13′′ high pressure resistant glass housings.
Its design started at the end of 2018 and after about two years it has been successfully deployed in summer 2020 in Cascadia Basin site, connected to the underwater Ocean Networks Canada infrastructure about 40 meters away from STRAW.
We present all the steps from the design to the realization of the mooring, with a special focus on the adopted technologies and on preliminary results of data taking.

Speaker: Immacolata Carmen Rea (TUM)
• 180
Time synchronization of Baikal-GVD clusters

Currently, the Baikal-GVD neutrino telescope consists of 7 clusters of 288 photodetectors. Each cluster is a functionally complete detector which can register events in stand-alone mode and jointly with other clusters. Joint operation of the clusters requires time synchronization with nanosecond accuracy. This paper presents the methods of time synchronization of the clusters, the results of a study of the synchronization accuracy using laser beacons, and first results of combining events from several clusters.

• Discussion: 42 Direct Dark Matter: Present and Future | DM 07

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• 181
DARWIN – a next-generation liquid xenon observatory for dark matter and neutrino physics

Benefiting from more than a decade of experience in WIMP searches with dual-phase xenon time projection chambers, the DARWIN (DARk matter WImp search with liquid xenoN) collaboration intends to build a next-generation detector involving 50 tonnes (40 tonnes active) of xenon. The primary goal of the observatory is to explore the entire experimentally accessible parameter space for WIMP masses above 5 GeV/c$^2$ down to the irreducible neutrino floor. With its low energy threshold and ultra-low background level, DARWIN will be an excellent platform to search for various other rare interactions. These include the neutrinoless double beta decay of $^{136}$Xe, a high-precision measurement of the low-energy solar neutrino flux, as well as searches for solar axions and axion-like-particles. In this talk, we will present the detector concept, the sensitivity to the various science channels, and ongoing R&D efforts.

Speaker: Mr Kevin Thieme (University of Zurich)
• 182
The DEAP-3600 experiment

The DEAP-3600 experiment searches for dark matter via the interactions of WIMPs with a liquid argon target. The experiment is located at SNOLAB in Sudbury, Ontario 2 km underground to shield the detector from cosmic rays. The detector consists of an acrylic sphere with an inner diameter of ~170 cm containing ~3300 kg of liquid argon. Liquid argon is chosen as a target due to its ability to reject electromagnetic backgrounds by examining its scintillation pulse shape. The argon volume is instrumented with 255 PMTs which are connected to the vessel via acrylic light guides. As liquid argon scintillates at a wavelength of 128 nm, its scintillation light needs to be shifted to a wavelength into a region where the PMTs are more sensitive; this is done by coating the inside of the acrylic vessel with TPB wavelength shifter, which re-emits the argon scintillation light at a wavelength of 420 nm.

This talk will describe the current status of the experiment and some recent analyses performed by the collaboration. The status of planned upgrades to the detector and the plans for the future of the experiment will also be detailed.

Speaker: Mark Stringer (Queen's University)
• 183
Simulations and background estimates for the DAMIC-M experiment

DAMIC-M (Dark Matter in CCDs at Modane) is a near-future experiment aiming to search for low-mass dark matter particles through their interactions with silicon atoms in the bulk of charge-coupled devices (CCDs). This technique was pioneered by the DAMIC experiment at SNOLAB. Its successor DAMIC-M will have a 25 times larger detector mass and will employ a novel CCD technology (skipper amplifiers) which allows to achieve a readout noise of 0.07 e-. With these novelties, DAMIC-M will reach unprecedented sensitivities to dark matter candidates of the so-called hidden sector. A challenging requirement is the control of the radiogenic background at the level of a fraction of events per keV per kg-day of target exposure. Accurate Geant4 simulations are being employed to optimise the detector design and drive the material selection and handling. This poster provides a comprehensive overview of the explored detector designs, the estimated background, and the strategies for its mitigation.

Speaker: Claudia De Dominicis
• 184
DIMS Experiment for Dark Matter and Interstellar Meteoroid Study

DIMS (Dark matter and Interstellar Meteoroid Study) is a new experiment aiming
to search for macroscopic dark matters and interstellar meteoroids. Nuclearites are nuggets of stable strange quark matter(SQM), neutral in charge and hypothetical super-heavy macroscopic particles (macros), and may be important components of the dark matter in our Universe. Nuclearites of galactic origins would have an expected typical velocity of about 220 km/s in galactic frame, whereas in the case of a head-on collision between interstellar meteoroids with a velocity that exceeds the escape velocity of the solar system and the Earth orbiting the Sun, the geocentric velocities will be larger than 72 km/s. We study the possibility to search for such fast-moving particles by using very high-sensitivity CMOS cameras with a wide field of view.
Based on observational data of meteor events using such stereo camera systems at some locations, we estimate the observable mass ranges for the moving nuclearites and the interstellar meteoroids. Observable flux limits are also estimated for these mass ranges.
We designed the DIMS experiment to search for such particles. In its first stage, the DIMS system consists of 4 high-sensitivity CMOS camera stations with a wide field of view. The system is going to be constructed at the Telescope Array cosmic-ray-experiment site in Utah, USA.
Details of the project science, plans and present status with preliminary test results will be reported in this paper.

Speaker: Prof. Fumiyoshi Kajino (Department of Physics – Konan University, Japan)
• 185
Sub-GeV dark matter and neutrino searches with Skipper-CCDs: status and prospects.

High-resistivity silicon has made possible the fabrication of thick fully-depleted charge-coupled devices (CCDs) that have found a wide range of scientific applications, from particle detection to astronomical imaging. Their low noise and high charge collection efficiency allow us to reach unprecedented sensitivity to physical processes with low-energy transfers. The newly-developed Skipper-CCD enhances this sensitivity by reducing the read-out noise reaching a sub-electron resolution. In this work, we introduce the fundamentals of the Skipper-CCD operation and the prospects for both sub-GeV dark matter searches and the detection of coherent elastic neutrino-nucleus scattering. A discussion of the challenges associated with the construction of the foreseen detectors with multi-kilogram target mass is also presented.

Speaker: Ana Martina Botti (IFIBA - UBA)
• 186
Results on low-mass weakly interacting massive particles from a 11 kg d target exposure of DAMIC at SNOLAB

Experimental efforts of the last decades have been unsuccessful in detecting WIMPs (Weakly Interacting Massive Particles) in the $10$-to-$10^4$ GeV/$c^2$ range, thus motivating the search for lighter dark matter. The DAMIC (DArk Matter In CCDs) at SNOLAB experiment aims for direct detection of light dark matter particles ($m_\chi < 10$ GeV/$c^2$) by means of CCDs (Charge-Coupled Devices). Fully-depleted 675 $\mu$m-thick CCDs are used to such end. The optimized readout noise and operation at cryogenic temperatures allow for a detection threshold of 50 eV$_{ee}$ electron-equivalent energy. Focusing on nuclear and electronic scattering as potential detection processes, DAMIC has so far set competitive constraints on the detection of low mass WIMPs and hidden-sector particles.
In this work, a 11 kg$\cdot$d exposure dataset is exploited to search for light WIMPs by building the first comprehensive radioactive background model for CCDs. Different background sources are discriminated making conjoint use of the spatial distribution and energy of ionization events, thereby constraining the amount of contaminants such as tritium from silicon cosmogenic activation and surface lead-210 from radon plate-out.
Despite a conspicuous, statistically-significant excess of events below 200 eV$_{ee}$, this analysis places the strongest exclusion limit on the WIMP-nucleon scattering cross section with a silicon target for $m_\chi < 9~$GeV/$c^2$.

Speaker: Michelangelo Traina (LPNHE, Paris, France)
• 187
Neutrinoless double beta decay search with XENON1T and XENONnT

With the lowest background level ever reached by detectors searching for rare-events, XENON1T proved to be the most sensitive dark matter direct detection experiment on earth. The unprecedented low level of radioactivity reached, made the XENON1T experiment suitable also for other interesting rare-events searches including the neutrinoless double beta decay of 136Xe. In this talk I will report on the current status of neutrinoless double beta decay of 136Xe search in XENON1T.

Furthermore, in the context of the advancement of the XENON program, the next generation experiment, XENONnT, designed with a high level of background reduction aiming to increase the predecessor sensitivity in rare-events searches is currently under commissioning phase in the underground National Laboratory of Gran Sasso (LNGS): it will host 5.9 tonnes of liquid xenon as a target mass.  I will also discuss the discovery potential of XENONnT in the search for neutrinoless double beta decay events and its general physics program.

Speaker: Maxime Pierre (Subatech)
• 188
Probing sterile neutrinos and axion-like particles from the Galactic halo with eROSITA

The nature of dark matter remains an open question and could be in the form of warm dark matter. Sterile neutrinos are well motivated warm dark matter candidates and can decay into photons through mixing, which are consequently detectable by X-ray telescopes for sterile neutrino mass in the keV range. Moreover, axion-like particle are compelling warm dark matter candidates too and they can couple to standard model particles and decay into photons at keV range. Both particles could explain the observed unidentified 3.5 keV line and, interestingly, XENON1T observed an excess at a few keV that can originate from axion-like particles, which is not yet excluded by X-ray constraints for a suppressed coupling to photons with respect to the coupling to electrons.
We study the diffuse emission coming from the Galactic halo, and test the sensitivity of all-sky X-ray survey eROSITA to identify a sterile neutrino or axion-like particle. By Monte Carlo method, we set bounds on the mixing angle of the sterile neutrinos and coupling strength of the axion-like particles. I will show that with eROSITA, we will be able to set stringent constraints, and in particular, we will be able to firmly probe the best-fit of the unidentified 3.5 keV line, where we reach an order of magnitude better sensitivity. Moreover, eROSITA is able to confirm an axion-like particle origin of the XENON1T excess for an excess greater than $\sim 3.5$ keV.

Speaker: Ariane Dekker
• Discussion: 48 Modelling AGN's spectral energy distribution | GAD-GAI-MM 04

#### 04

• 189
Gamma Rays from Fast Black-Hole Winds

Massive black holes at the centers of galaxies can launch powerful wide-angle winds, which if sustained over time, can unbind the gas from the stellar bulges of galaxies. These winds, also known as ultra-fast outflows (UFOs), may be responsible for the observed scaling relation between the masses of the central black holes and the velocity dispersions of stars in galactic bulges. Propagating through the galaxy, the wind should interact with the interstellar medium creating a strong shock, similar to those observed in supernovae explosions, which is able to accelerate charged particles to high energies. In this talk I will present the Fermi Large Area Telescope detection of gamma-ray emission from these shocks in a small sample of galaxies exhibiting energetic winds. The detection implies that energetic black-hole winds transfer ~0.04% of their mechanical power to gamma rays and that the gamma-ray emission represents the onset of the wind-host interaction.

Speaker: Chris Karwin (Clemson University)
• 190
Gamma-ray emission from young radio galaxies and quasars

According to radiative models, radio galaxies are predicted to produce gamma rays from the earliest stages of their evolution onwards. The study of the high-energy emission from young radio sources is crucial for providing information on the most energetic processes associated with these sources, the actual region responsible for this emission, as well as the structure of the newly born radio jets.
Despite systematic searches for young radio sources at gamma-ray energies, only a handful of detections have been reported so far. Taking advantage of more than 11 years of Fermi-LAT data, we investigate the gamma-ray emission of 162 young radio sources (103 galaxies and 59 quasars), the largest sample of young radio sources used so far for a gamma-ray study. We analyse the Fermi-LAT data of each individual source separately to search for a significant detection. In addition, we perform the first stacking analysis of this class of sources in order to investigate the gamma-ray emission of the young radio sources that are undetected at high energies.
We report the detection of significant gamma-ray emission from 11 young radio sources, including the discovery of significant gamma-ray emission from the compact radio galaxy PKS 1007+142.
Although the stacking analysis of below-threshold young radio sources does not result in a significant detection, it provides stringent upper limits to constrain the gamma-ray emission from these objects.
In this talk we present the results of our study and we discuss their implications for the predictions of gamma-ray emission from this class of sources.

Speaker: Giacomo Principe (INFN / University of Trieste)
• 191
A two-zone emission model for Blazars and the role of Accretion Disk MHD winds

Blazars are a sub-category of radio-loud active galactic nuclei with relativistic jets pointing towards the observer. They exhibit non-thermal variable emission, which practically extends over the whole electromagnetic spectrum. Despite the plethora of multi-wavelength observations, the origin of the emission in blazar jets remains an open question. In this work, we construct a two-zone leptonic model: particles accelerate in a small region and lose energy through synchrotron radiation and inverse Compton Scattering. Consequently, the relativistic electrons escape to a larger area where the ambient photon field, which is related to Accretion Disk MHD Winds, could play a central role in the gamma-ray emission. This model explains the Blazar Sequence and the broader properties of blazars, as determined by Fermi observations, by varying only one parameter, the mass accretion rate onto the central black hole. Flat Spectrum Radio Quasars have a strong ambient photon field and their gamma-ray emission is dominated by the more extensive zone, while in the case of BL Lac objects, the negligible ambient photons make the smaller (acceleration) zone dominant.

Speaker: Stella Boula (National and Kapodistrian University of Athens)
• 192
Building a robust sample of Fermi-LAT blazars that exhibit periodic gamma-ray emission

Blazars can show variability on a wide range of timescales. However, the search for periodicity in the gamma-ray emission of blazars remains an on-going challenge. This contribution will show the results obtained when a systematic pipeline is used to implement ten well-established methods for searching for periodicity. We analyze the most promising candidates selected from our previous work, extending the Fermi-LAT light curves over three more years, for a total telescope time of twelve years. These improvements have allowed us to build the first sample of blazars that display a periodicity detected at a significance >5sigma. Finally, we will discuss the potential origins for the periodic behavior observed in blazars.

Speaker: Pablo Peñil (Clemson University)
• 193
VHE gamma-ray spectral hint of two-zone emitting region in Mrk 501

Markarian 501 (Mrk 501) is one of the brightest very high energy (VHE, E> 100 GeV) gamma-ray blazars. It is located in our neighborhood, at redshift z = 0.034. During a multi-wavelength campaign in July 2014, Mrk 501 displayed the highest X-ray activity observed by the Neil Gehrels Swift X-ray telescope (XRT) since its launch. The X-ray spectra displayed during this flaring episode were very hard, and showed variability on nightly timescales. On 2014 July 19, in coincidence with the peak of the X-ray activity, a hint of a narrow feature at ~3 TeV was observed with the MAGIC telescopes. Such feature makes the VHE spectrum inconsistent with the classical analytic functions used to describe the measured VHE spectra (power law, log-parabola, and log-parabola with exponential cutoff) at more than 3σ. A double-log-parabola fit is preferred w.r.t. a single one at more than 4σ confidence level. Three different scenarios that could produce such an effect are discussed: (a) a pileup in the electron energy distribution; (b) a two-zone Synchrotron Self-Compton (SSC) emission model; and (c) a pair cascade model. In this contribution we will present the observational details and a general overview of the possible physical mechanisms of this unprecedented observation.

Speaker: Josefa Becerra González (Insituto de Astrofísica de Canarias & Universidad de La Laguna)
• 194
Multiwavelength observations in 2019-2020 of a new very-high-energy gamma-ray emitter: the flat spectrum radio quasar QSO B1420+326

The flat-spectrum radio quasar QSO B1420+326 underwent an enhanced gamma-ray flux state seen by Fermi-LAT at the turn of 2019/2020. Compared to the low state both the position and luminosity of the two spectral energy distribution peaks changed by at least two orders of magnitude. The high state resulted in the discovery of the very-high-energy (>100 GeV) gamma-ray emission from the source by the MAGIC telescopes. The organized multiwavelength campaign allow us to trace the broadband emission of the source through different phases of the flaring activity. The source was observed by 20 instruments in radio, near-infrared, optical, ultra-violet, X-ray and gamma-ray bands.
We use dedicated optical spectroscopy results to estimate the accretion disk and the dust torus luminosity. The optical spectroscopy shows a prominent FeII bump with flux evolving together with the continuum emission and a MgII line with varying equivalent width. The gamma-ray flare was accompanied by a rotation of the optical polarization vector and emission of a new superluminal radio knot. We model spectral energy distributions in different flare phases in the framework of combined synchrotron-self-Compton and external Compton scenario in which the
shape of the electron energy distribution is determined from cooling processes.

Speaker: Filippo D'Ammando (INAF-IRA Bologna)
• 195

Beams of ultra-relativistic electrons in blazar jets develop pair cascades interacting with ambient soft photons. Employing coupled kinetic equations with escape terms, we model the unsaturated pair cascade spectrum. We assume that the gamma rays predominantly scatter off recombination-line photons from clouds photoionised by the irradiation from the accretion disk and the jet. The cascade spectrum is rather insensitive to the injection of hard electron spectra associated with the short-time variability of blazars. Adopting physical parameters representative of Markarian 501 and 3C 279, respectively, we numerically obtain spectral energy distributions showing distinct features imprinted by the recombination-line photons. The hints for a peculiar feature at 3 TeV in the spectrum of Markarian 501, detected with the MAGIC telescopes during a strong X-ray flux activity in 2014 July, can be explained in this scenario as a result of up-scattering of line photons by beam electrons and the low pair-creation optical depth. Inspecting a high-fidelity Fermi-LAT spectrum of 3C 279 reveals troughs in the spectrum that coincide with the threshold energies for gamma rays producing pairs in collisions with recombination-line photons and the absence of exponential attenuation. Our finding implies that the gamma rays in 3C 279 escape from the edge of the broad emission line region.

Speaker: Christoph Wendel (JMU Würzburg)
• 196
Detection of new Extreme BL Lac objects with H.E.S.S. and SWIFT

Extreme high synchrotron peaked blazars (EHBLs) are amongst the most powerful accelerators found in nature. Usually the synchrotron peak frequencyof an EHBL is above 10^17 Hz, i.e., lies in the range of medium to hard X-rays making them ideal sources to study particle acceleration and radiative processes. EHBL objects are commonly observed at energies beyond several TeV, making them powerful probes of gamma-ray absorption in the intergalactic medium. During the last decade, several attempts have been made to increase the number of EHBL detected at TeV energies and probe their spectral characteristics.
Here we report new detections of EHBLs in the TeV energy regime, each at a redshift of less than 0.25, by the High Energy Stereoscopic System (H.E.S.S.). Also, we report on X-ray observations of these EHBLs candidates with Swift XRT. In conjunction with the very high energy observations, this allows us to probe the radiation mechanisms and the underlying particle acceleration processes.

Speaker: Ms Angel Priyana Noel (Astronomical Observatory of Jagiellonian University)
• 197
Discovery of TXS 1515-273 at VHE gamma-rays and modelling of its Spectral Energy Distribution

In February 2019, a flaring state of the extreme blazar candidate TXS 1515-273 was registered by the Fermi-LAT, which triggered observations with the MAGIC telescopes and the X-ray satellites Swift, XMM-Newton and NuStar. The observations led to the discovery of the source at VHE gamma-rays and the detection of short time scales of variability (~1 h) in several X-ray bands.
The analysis of the observed variability helped us to constrain the emission region’s physical parameters. Thanks to the high-quality X-ray data, the synchrotron peak location was determined. The source was classified as a high synchrotron peaked source during the flaring activity. We constructed the broadband spectral energy distribution from radio to TeV. We interpreted it assuming leptonic emission and taking into account the constraints from the X-ray variability. We tested two scenarios: a simple one-zone model and a two-component model. Both models were found to describe well the data from X-rays to VHE gamma rays, but the two-zone model allows for a more accurate modelling of the emission at radio and optical energies.

Speaker: Serena Loporchio (University and INFN - Bari)
• 198
Explaining the TeV detection of blazar AP Librae: constraints from ALMA and HST

Powerful jets hosted by accreting super-massive black holes have long been candidates for the acceleration sites for high-energy extra-galactic cosmic rays, supported by the recent association of neutrinos from blazar TX0506+056. In the highly-aligned jets known as blazars, the X-ray to TeV radiation is usually attributed to inverse Compton scattering processes, but has not been clearly identified in most cases due to degeneracies in physical models. AP Librae, a blazar detected in TeV energies, has an extremely broad high-energy spectrum, covering ∼ 9 decades in energy. Using new ALMA and Hubble imaging of the kpc-scale jet and over 11 years of Fermi/LAT observations, we rule out previously proposed leptonic models attributing the high-energy emission to synchrotron self-Compton from the jet base and IC/CMB in the kpc-scale jet. In contrast, "lepto-hadronic" models remain viable, though underconstrained given the number of free parameters. We find that the origin of the TeV photons from this source remains debatable and show that leptonic and hadronic models can be further tested with deep and high dynamic range imaging in the sub-mm and far infrared and/or continued monitoring of the source at TeV energies to test for variability. Unmasking the origin of extragalactic TeV emission from blazar AP Librae would unlock vital clues to our understanding of particle acceleration and the origin of extra-galactic cosmic rays.

Speaker: Agniva Roychowdhury (University of Maryland Baltimore County)
• 199
Exploring the High-Energy Gamma-Ray Spectra of TeV Blazars

The highest-energy blazars exhibit non-thermal radiation extending beyond 1 TeV with high luminosities and strong variabilities, indicating extreme particle acceleration in their relativistic jets. The gamma-ray spectra of blazars contain information about the distribution and cooling processes of high-energy particles in jets, the extragalactic background light between the source and the observer, and potentially, the environment of the gamma-ray emitting region and exotic physics that modifies the opacity of the universe to gamma rays. We use data from Fermi-LAT and VERITAS to study the variability and spectra of a sample of TeV blazars across a wide range of gamma-ray energies, taking advantage of more than ten years of data from both instruments. The variability in both GeV and TeV gamma-ray bands is investigated using a Bayesian blocks method to identify periods with a steady flux, during which the average gamma-ray spectra, after correcting for the pair absorption effect from propagation, can be parameterized without the risk of mixing different flux states. We report on the search for intrinsic spectral curvature and spectral variability in these blazars, in an effort to understand the physical mechanisms behind the high-energy gamma-ray spectra of TeV blazars.

Speaker: Dr Qi Feng (Barnard College / Columbia University)
• 200
Extreme blazars under the eyes of MAGIC

Extreme high-frequency-peaked BL Lac objects (EHBLs) are the most energetic persistent sources in the universe. This contribution reports on long-term observing campaigns of tens of EHBLs that have been organized by the MAGIC collaboration to enlarge their population at VHE and understand the origin of their extreme properies. EHBLs are characterized by a spectral energy distribution (SED) featuring a synchrotron peak energy above 1 keV. Several EHBLs display a hard spectral index at very high energies (VHE; E>100 GeV), suggesting a gamma-ray SED component peaking significantly above 1 TeV. Such extreme properties are challenging current standard emission and acceleration mechanisms. Recent studies have also unveiled intriguing disparities in the temporal characteristics of EHBLs. Some sources seem to display a persistent EHBL behaviour, while others belong to the EHBL family only temporarily.
We will focus on the recent results of the first hard-TeV EHBL catalog. The MAGIC observations are accompanied by an extensive multi-wavelength coverage to obtain an optimal determination of the SED. This allow us to investigate leptonic and hadronic scenarios for the emission. We will also present the recent detection of the EHBL 1RXS0812.0+0237 in the VHE band by MAGIC. Finally, we will discuss a broad multi-wavelength campaign on the BL Lac type object 1ES2344+514, which showed intermittent EHBL characteristics in August 2016.

Speaker: Axel Arbet-Engels (ETH Zürich, Switzerland)
• 201
MAGIC and H.E.S.S. detect VHE gamma rays from the blazar OT081 for the first time: a deep multiwavelength study

OT081 is a luminous blazar well known for its variability in many energy bands.
The very-high-energy (VHE, E > 100 GeV) gamma-ray emission from the source was discovered by MAGIC and H.E.S.S. during flaring activity in July 2016, after a trigger from the LAT onboard the Fermi satellite.
From the analysis of the multiwavelength (MWL) light curves and of the broadband spectral energy distribution (SED), we study the activity of the source, in particular during four identified states of activity in the window MJD 57575 to MJD 57600. The intrinsic gamma-ray spectrum can be described by a power law with spectral indices of 3.27+/- 0.44 (MAGIC) and 3.39 +/- 0.58 (H.E.S.S.) for energy ranges 60-300 GeV and 120-500 GeV, respectively.
The combined contemporaneous HE (E > 100 MeV) through VHE SED shows curvature and can be described by a log-parabola shape.
VLBI analysis of the flare reveals the ejection of a superluminal knot and its subsequent passage through a stationary feature as a possible cause of the HE gamma-ray activity.
A simple one-zone synchrotron self-Compton (SSC) model is not sufficient to describe the broadband SED, and external Compton is required to explain the high Compton dominance displayed by the source.
The presence of broad emission lines in the optical spectrum of the source challenges the categorization of OT081 as a BL Lac and, together with the emission scenarios tested, points to the possibility that the source is transitional in nature between a BL Lac and a flat spectrum radio quasar (FSRQ).

Speaker: Marina Manganaro (University of Rijeka, Department of Physics)
• 202
Modeling the non-flaring VHE emission from M87 as detected by the HAWC gamma ray observatory

M87 is a giant radio galaxy located in the Virgo Cluster, known to be a very high energy (VHE) gamma-ray source. As radio galaxies are considered the misaligned low-redshift counterparts of blazars, they are excellent laboratories for testing AGN emission models. M87 has been detected and monitored by Fermi-LAT and several atmospheric Cherenkov telescopes. Recently, the HAWC Collaboration has reported weak evidence of long-term TeV gamma-ray emission from this source. However, HAWC data has the potential to constrain the average VHE emission of sources of complex behavior, like M87, for which the physical origin of the VHE gamma-ray emission is still uncertain. We fitted a lepto-hadronic scenario to the broadband spectral energy distribution of M87 to model its non-flaring VHE emission using HAWC data

Speaker: Fernando Ureña Mena (Instituto Nacional de Astrofísica, Óptica y Electrónica, Tonantzintla, Puebla, Mexico)
• 203
TeV emission from FSRQs: The first systematic and unbiased survey

Flat spectrum radio quasars (FSRQs) have been detected at TeV energies by ground-based atmospheric Cherenkov telescope mainly during flaring states. VERITAS is carrying out the first systematic and unbiased search for TeV emissions from a set of FSRQs. Fermi-LAT-detected FSRQs with positive declinations and extrapolated fluxes from the 3FHL catalog exceeding 1% Crab at >200 GeV after correcting for EBL absorption were selected for this survey, resulting in eight targets. Additionally, four FSRQs that were already detected at TeV energies are also included in this survey. In an unbiased fashion, the observations of twelve FSRQs, even without detection, provide the first constraints on the duty cycle of TeV emission from these FSRQs. Constraints on the TeV fluxes from these sources are used to probe the origin of the GeV to TeV spectral breaks. From this ongoing survey, the results of the sources observed during 2020-21 season are discussed in this work.

Speaker: Sonal Ramesh Patel (ZEU-CTA (CTA))
• 204
The luminosity function of TeV-emitting BL Lacs: observations of an HBL sample with VERITAS

High-frequency-peaked BL Lacs (HBLs) dominate the extragalactic TeV sky, with more than 50 objects detected by the current generation of TeV observatories. Still, the properties of TeV-emitting HBLs as a population are poorly understood due to biases introduced by the observing strategies of Cherenkov Telescopes, limiting our ability to estimate the potential contribution of TeV blazars to the diffuse neutrino, gamma-ray, and cosmic-ray backgrounds as well as their role in the late-stage evolution of active galactic nuclei. The VERITAS Collaboration has designed a program to quantify and minimize observational biases by selecting a sample of 36 HBLs and measuring their TeV fluxes at times that are not motivated by high-flux states. First results from this survey, which is the basis for a measurement of the luminosity function of TeV-emitting HBLs, will be presented at the conference.

Speaker: Manel Errando (Washington Uhniversity in St Louis)
• Wednesday, July 14
• Discussion: 04 CR Energy Spectrum | CRI 03

#### 03

• 205
Energy spectrum of cosmic rays measured using the Pierre Auger Observatory

We present the energy spectrum of cosmic rays measured at the Pierre Auger Observatory from $6 \times 10^{15}$ eV up to the most extreme energies where the accumulated exposure reaches about 80 000 km$^2$ sr yr. The wide energy range is covered with five different measurements, namely using the events detected by the surface detector with zenith angles below 60 degrees and applying different reconstruction method also above 60 degrees, those collected by a denser array, the hybrid events simultaneously recorded by the surface and fluorescence detectors, and using those events in which the signal is dominated by Cherenkov light registered by the high-elevation telescopes. In this contribution, we report updates of the analysis techniques and present the spectrum obtained by combining the five different measurements. Spectral features occurring in the wide energy range covered by the Observatory are discussed.

Speaker: Vladimír Novotný (IPNP, Charles University, Prague)
• 206
Energy spectrum and the shower maxima of cosmic rays above the knee region measured with the NICHE detectors at the TA site

The Non-Imaging CHErenkov Array (NICHE) is a low energy extension to Telescope Array (TA) using an array of closely spaced (~100 m) light collectors covering an area of ~2 square km. It is being deployed in the field-of-view of the FD for the TA Low Energy Extension (TALE) and overlaps with the TALE FD in the energy range above 2 PeV. Cosmic ray air showers with energies 1-100 PeV will be reconstructed using the Lateral Distribution of Cherenkov light from the air showers. This method allows shower energy and the maximum of shower depth (Xmax) to be determined. A prototype of the array, j-NICHE, has been making routine observations with 14 detectors since May, 2019. We will present the latest results of NICHE including the energy spectrum and the shower maximum distribution around the cosmic ray knee.

Speaker: Yugo Omura (Osaka City University)
• 207
The all-particle cosmic ray energy spectrum measured with HAWC

Thanks to recent technological development, a new generation of experiments have been developed with more sensitivity in the energy interval from 10 TeV to 1 PeV, such as HAWC. Due to its designs and high altitude, the HAWC air shower observatory can provide a bridge between the data from direct and indirect cosmic ray detectors. In 2017 the HAWC collaboration published their first results on the energy spectrum of cosmic rays, in the range from 10 to 500 TeV. This work updates these results by extending the energy interval of the measured all-particle cosmic-ray energy spectrum up to 1 PeV. The energy spectrum was obtained from the analysis of two years of HAWC's data using an unfolding method. We employed the QGSJET-II-04 model for the energy calibration and the spectrum reconstruction. The results confirm the presence of a knee like feature around 45 TeV, which was reported by the HAWC collaboration in 2017.

Speaker: Mr Jorge Antonio Morales-Soto (Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo)
• 208
Protons Spectrum from MAGIC Telescopes data

Abstract Imaging Atmospheric Cherenkov telescopes (IACTs) are designed to detect cosmic gamma rays. As a by-product, IACTs detect Cherenkov flashes generated by millions of hadronic air showers every night. We present the proton energy spectrum from several hundred GeV to several hundred TeV, retrieved from the hadron induced showers detected by the MAGIC telescopes. The protons are discriminated from He and heavy nuclei with machine learning classification. The energy estimation is based on a specially developed deep neural network regressor. In the last decade, Deep Learning methods gained much interest in the scientific community for their ability to extract complex relations in data and process vast quantities of data in a short time. The proton energy spectrum obtained in this work is compared with the spectra obtained by modern cosmic ray experiments.

Speaker: Petar Temnikov (Institute for Nuclear Research and Nuclear Energy Sofia)
• 209
Joint analysis of the energy spectrum of ultra-high-energy cosmic rays as measured at the Pierre Auger Observatory and the Telescope Array

The measurement of the energy spectrum of ultra-high-energy cosmic rays (UHECRs) is of crucial importance to clarify their origin and acceleration mechanisms. The Pierre Auger Observatory in Argentina and the Telescope Array (TA) in the US reported their measurements of UHECR energy spectra observed in the southern and northern hemisphere, respectively. The region of the sky accessible to both Observatories ([-15,+24] degrees in declination) can be used to cross-calibrate the two spectra.
The Auger-TA energy spectrum working group was organized in 2012 and has been working to understand the uncertainties in energy scale in both experiments, their systematic differences, and differences in the shape of the spectra. In previous works, we reported that there was an overall agreement of the energy spectra measured by the two observatories below 10 EeV while at higher energies, a remaining significant difference was observed in the common declination band. We revisit this issue to understand its origin by examining the systematic uncertainties, statistical effects, and other possibilities. We will also discuss the differences in the spectra in different declination bands and a new feature in the spectrum recently reported by the Auger Collaboration.

Speaker: Yoshiki Tsunesada (Osaka City University)
• 210
TA Monocular Spectrum Measurement

The Telescope Array (TA) Cosmic Ray Observatory is the largest cosmic ray detector in the northern hemisphere. TA was built to study ultra-high-energy cosmic rays (UHECRs), cosmic rays with energies above 1 EeV. TA is a hybrid detector, employing both a surface detector array and fluorescence telescopes. We present a measurement of the cosmic ray energy spectrum for energies above $10^{17.5}$ eV using only the fluorescence telescopes. A new, machine-learning based, weather classification scheme was used to select data parts with good weather and ensure the quality of the fluorescence data. The data from the Black Rock Mesa (BR) and Long Ridge (LR) fluorescence telescope stations were analyzed separately in monocular mode, with the calculated fluxes combined into a single spectrum. We present fits of the combined spectrum to a series of broken power law models. A three-times-broken power law gives the best fit. The three breaks suggest an additional feature of the spectrum between the previously observed Ankle and the GZK suppression.

Speaker: Douglas Bergman (University of Utah)
• 211
Cosmic ray energy spectrum in the 2nd knee region measured by the TALE-SD array

The Telescope Array Low energy Extension (TALE) experiment in Utah, U.S.A., consists of 10 atmospheric fluorescence telescopes and 80 Surface Detectors (SDs) spread over an area of 21 $km^2$. The SD array consists of 40 SDs at 400 m spacing and 40 SDs at 600 m spacing. The TALE-SD was completed in February 2018 and has been in steady operation since then, triggering at a rate of about 30 air shower events in 10 minutes. We have developed the software to measure the energy spectrum of cosmic rays from the data obtained by TALE-SD. The performance of the software was evaluated by using air shower events generated by Monte Carlo simulation. We estimate that when the energy of the primary cosmic ray is $10^{18.0}$eV, the accuracy of energy determination is 15%, the accuracy of arrival direction determination is 1.5°, and the aperture is 15 $km^2$ sr. Furthermore, we obtained the energy spectrum of cosmic rays from the actual data obtained by the TALE-SD array from October to the end of November 2019. In this presentation, I will report these results.

Speaker: Koki Sato (Osaka city university)
• 212
Cosmic Ray Energy Spectrum measured by the TALE Fluorescence Detector

The Telescope Array (TA) cosmic rays detector located in the State of Utah in the United States is the largest ultra high energy cosmic rays detector in the northern hemisphere. The Telescope Array Low Energy Extension (TALE) fluorescence detector (FD) was added to TA in order to lower the detector's energy threshold, and has succeeded in measuring the cosmic rays energy spectrum and mass composition down to PeV energies. In this contribution we describe the measurement of the cosmic ray energy spectrum using $\sim4$ years of TALE FD data. The energy spectrum shows features consistent with the "knee" and the "second knee".

Speaker: Tareq AbuZayyad (Loyola University Chicago; University of Utah)
• 213
Preliminary Cosmic Ray Results from the HAWC's Eye Telescopes

The compact imaging air-Cherenkov telescope HAWC’s Eye was developed to operate together with the High-Altitude Water Cherenkov Gamma-Ray Observatory (HAWC). The combination of both detection techniques in a hybrid setup provides a significant improvement in energy and angular resolution, aiming for improved measurements of the cosmic ray composition above 10 TeV and contributing to the physics program of the observatory. Preliminary results of the first hybrid measurements of the cosmic ray spectrum are presented. A second HAWC's Eye telescope was successfully commissioned at the HAWC site in 2019. Two measurement nights since then recorded the data used in this analysis. The HAWC's Eye events were successfully synchronized with HAWC and further used to characterize the hybrid system. A complete simulation of the hybrid configuration was used to develop algorithms to reconstruct the energy and arrival direction of proton-induced air showers. Those algorithms were successfully applied to the measured cosmic ray events to analyze the improved performance of the hybrid detection. The spectrum reconstructed with HAWC's Eye is compatible with the spectrum reconstructed solely from the coincident HAWC data.

Speaker: Florian Rehbein (RWTH Aachen University)
• 214
Recent measurement of the Telescope Array energy spectrum and observation of the shoulder feature in the Northern Hemisphere

The Telescope Array (TA) is a hybrid cosmic ray detector deployed in 2007 in Millard County, Utah, USA, which consists of a surface detector of 507 plastic scintillation counters spanning a 700 km$^2$ area on the ground that is overlooked by three fluorescence detector stations. The High Resolution Fly's Eye (HiRes) experiment is a predecessor of TA, which consisted of two fluorescence detector stations operating from 1997 until 2006 from Dugway Proving Ground, Utah, USA, and which was the the first cosmic ray experiment with sufficient resolution and exposure to successfully observe the Greisen–Zatsepin–Kuzmin (GZK) suppression at 10$^{19.75}$ eV. In this work, we present an updated TA energy spectrum result and a joint fit of independent spectrum measurements by the TA surface detector, TA fluorescence detector, and HiRes fluorescence detector to a broken power law function, which exhibits the ankle, GZK suppression, and the new shoulder feature initially seen by the Pierre Auger Observatory in the Southern Hemisphere. HiRes and TA observe the shoulder feature in the Northern Hemisphere at 10$^{19.25}$ eV, with a statistical significance of 5.3 standard deviations.

Speaker: Dmitri Ivanov (University of Utah)
• 215
Study of Energy Measurement of Cosmic Ray Nuclei with LHAASO

The Large High Altitude Air Shower Observatory(LHAASO) is a hybrid extensive air shower(EAS) array with an area of about 1km2 at an altitude of 4410 m a.s.l. in Sichuan province, China. It contains three sub-detectors: 1 km2 array (LHAASO-KM2A) composed of electromagnetic particle (ED) and muon detectors (MD); water Cherenkov detector array(LHAASO-WCDA) and 18 wide field-of-view air Cherenkov telescopes(LHAASO-WFCTA). One of the main scientific goals is measuring the individual energy spectra of cosmic rays from ~30TeV to a couple of EeV. Up to now, the whole WCDA, ¾ of KM2A, 16 telescopes have been in operation. In this paper, the energy reconstruction method and result of cosmic ray nuclei based on KM2A and WFCTA simulated events will be shown, the reconstructed energy difference between KM2A and WFCTA is also compared between data and MC.

Speaker: hu liu (Southwest Jiaotong University, China)
• 216
The Energy Spectrum of Cosmic Ray Proton and Helium above 100TeV Measured by LHAASO Experiment

The determination of energy spectrum of different species above 100 TeV is still one of the main challenges in cosmic ray physics. The energy spectrum of the individual component is an important tool to investigate the cosmic ray production and propagation mechanisms. A preliminary results of mixed proton and helium energy spectrum, obtained with the combined data of six Cherenkov telescopes, one 150m×150m water Cherenkov detector (WCDA-1) and half muon detector and scintillator detector array in LHAASO experiment will be reported. The preliminary results will be analyzed by using the combined data obtained between October 2020 and February 2021. By means of a multiparameter technique, the resolution of reconstructed energy, shower direction, shower core location and composition identification are improved.

Speaker: Zhiyong You (The Institute of High Energy Physics of the Chinese Academy of Sciences)
• Discussion: 20 GCR long-term modulation | SH 07

#### 07

• 217
Combined heliospheric modulation of galactic protons and helium nuclei from solar minimum to maximum activity related to observations by PAMELA.

The global features of the modulation of galactic cosmic ray protons and helium nuclei are studied in the heliosphere from solar minimum to maximum activity with a comprehensive, three-dimensional, drift model and compared to proton and helium observations measured by PAMELA from 2006 to 2014. Combined with accurate very local interstellar spectra (VLIS) for protons and helium nuclei, this provides the opportunity to study in detail how differently the proton to helium ratio, over a wide range of rigidities, behaves towards increasing solar activity. In particular, the effects at the Earth of the difference in their VLIS’s, mass-to-charge ratio (A/Z) and those caused by the main modulation mechanisms will be illustrated from solar minimum to maximum activity.

Speaker: Dr Donald Ngobeni (1. Centre for Space Research, North-West University, Potchefstroom, South Africa; 2. School of Physical & Chemical Sciences, North-West University, Mmabatho, South Africa)
• 218
Spectral parameterization of GCR observations and reconstruction of solar modulation parameters derived from the Convection-Diffusion approximation

Galactic cosmic rays (GCRs) entering the heliosphere and propagating towards Earth are subject to various modulation processes including drifts, convection, adiabatic energy changes, and diffusion as a result of the turbulent solar wind. This transport can be described by the Parker equation (Parker, 1965). A widely used first-order approximation of the Parker equation is the Force-Field approximation (FFA), while a similar approximation, the Convection-Diffusion approximation (CDA) is rarely applied. Using PAMELA and AMS-02 observations, the validity of the FFA and the CDA in the energy range 1 MeV to 20 GeV was investigated. The resulting modulation parameters and the effective diffusion coefficient, derived from both approximations over a complete 11-years solar cycle, were compared. Our results show that the CDA appears to be significantly more accurate than the FFA in reproducing the measurements, while the resulting transport parameters are highly dependent on the choice of the local interstellar spectrum and the assumed diffusion coefficient parameters. Based on these findings, we therefore propose to use the CDA as a more suitable approximation than the widely used FFA for space weather applications, especially for dosimetric studies where an accurate GCR parametrization is essential.

Speaker: Moshe Godfrey Mosotho (Center for Space Research, North-West University, South Africa)
• 219
Solar Modulation During the Descending Phase of Solar Cycle 24 Observed with CALET on the International Space Station

The CALorimetric Electron Telescope (CALET) installed on the International Space Station has multiple event trigger modes for measuring cosmic-ray (CR) particles and gamma rays, and the observations of the low-energy CRs have been successfully performed by a Low-Energy Electron (LEE) shower trigger mode that is active only at high geomagnetic latitude. Continuous measurements of low-energy CRs with LEE trigger of the CALET have detected the charge sign dependence of the solar modulation. In this talk, we present the latest results of the low-energy electron fluxes observed by CALET during the descending phase of the solar cycle 24. We also present the long-term variations of count rates of the CR electrons and protons, discussing the charge sign dependence of the solar modulation.

Speaker: Shoko Miyake
• 220
On the transition from 3D to 2D transport equations for a study of long-term cosmic-ray intensity variations in the heliosphere

We consider in our study the exact two-dimensional (2D) transport equation (TPE) for galactic cosmic ray (GCR) intensity in the heliosphere, averaged over longitude, and derived by averaging the full three-dimensional (3D) steady-state TPE over longitude. As we showed before, this exact 2D TPE is equal to that with the averaged 3D TPE coefficients but with the “source-term” Q2D due to 3D modulation effects. In particular, Q2D is equal to the longitude convolution of the longitudinal variances of the coefficients as used in the 3D TPE and as applicable to the modulation of GCR intensity. In our previous work we also suggested an expression (Q ̌_2D) for Q2D when estimated without solving the 3D TPE for the simplest case of the only characteristic, heliospheric feature depending on helio-longitude is the polarity of the solar magnetic field.
This study is focused on calculating the term Q ̃_2D equal to the same longitude convolution as Q2D when solving numerically the steady-state 3D TPE for the above mentioned simplest case. For cases of close similarity between Q ̃_2D and Q ̌_2D, we come to the conclusion that the 2D approach with Q ̌_2D can be used with confidence in the study of the long-term modulation of GCRs instead of using the complex way of solving the full 3D TPE for this simplest case. However, if the calculated (Q ̃_2D) and estimated (Q ̌_2D) terms are found to be different, the application of the complex way seems inevitable.
This work is supported in part by RU-SA NRF-RFBR grant No. 19-52-60003 SA-t.

Speaker: Mikhail Krainev (Lebedev Physical Institute, Moscow, Russia)
• 221
Galactic cosmic-ray hydrogen spectra in the 40-300MeV range measured by the High-energy Particle Detector (HEPD) on board the CSES-01 satellite during the current solar minimum

The High-Energy Particle Detector (HEPD) onboard the China Seismo-Electromagnetic Satellite (CSES-01) - launched in February 2018 - is a light and compact payload suitable for measuring electrons (3-100 MeV), protons (30-300 MeV), and light nuclei (up to a few hundreds of MeV) with a high energy resolution and a wide angular acceptance. The very good capabilities in particle detection and separation, together with the Sun-synchronous orbit, make HEPD well suited for galactic particles and solar modulation studies. We report here some insights on the data-analysis techniques employed for this kind of study; as a result, semiannual galactic hydrogen differential energy spectra between 40 and 250 MeV for the period between the end of the 24th and the start of the 25th solar activity cycle, are presented . Moreover, a brief discussion on the comparison with theoretical spectra obtained from the HelMod 2D Monte Carlo model is also presented.

Speaker: Matteo Martucci (University of Rome Tor Vergata)
• 222
A simulation study of galactic proton modulation from solar minimum to maximum conditions

The observation of various cosmic ray particles at the Earth had been done with the PAMELA space detector for almost 10 years, from June 2006 to January 2016. The AMS-02 space experiment provides similar cosmic ray data. The purpose of this work is to utilize the available state-of-the-art numerical modulation model for the transport of cosmic rays in the heliosphere to compute the modulation of galactic protons from minimum to maximum solar activity. These modeling results, which simulate realistic heliospheric conditions, are compared to proton observations from PAMELA taken between 2006 and 2014 and to similar AMS-02 observations after 2011. It will be shown how differently modulation mechanisms influence the time-evolution of the proton spectra when modulation conditions change from minimum to maximum.

Speaker: Dr Dzivhuluwani Ndiitwani (Centre for Space Research, North-West University, Potchefstroom, South Africa; School of Physical & Chemical Sciences, North-West University, Mmabatho, South Africa)
• 223
A full solar cycle of proton and helium measurements

Time-dependent energy spectra of galactic cosmic rays (GCRs) carry fundamental information regarding their origin and propagation. When observed at the Earth, these spectra are significantly affected by the solar wind and the imbedded solar magnetic field that permeates the heliosphere, changing significantly over an 11-year solar cycle. Energy spectra of GCRs measured during different epochs of solar activity provide crucial information for a thorough understanding of solar and heliospheric phenomena. The PAMELA experiment had collected data for almost ten years (15 June 2006 - 23 January 2016), including the minimum phase of solar cycle 23 and the maximum phase of solar cycle 24. Here, we present spectra for protons and helium nuclei measured by the PAMELA instrument from 2006 to 2014. Time profiles of the proton-to-helium flux ratio at various rigidities are also presented, allowing the study of all characteristic features resulting from their different mass-to-charge ratio and the difference in the shape of their respective local interstellar spectra.

Speaker: Nadir Marcelli (INFN sezione di Roma)
• 224
Galactic Cosmic-Ray Intensities During three Solar Minima

The Cosmic-Ray Isotope (CRIS) and Solar Isotope Spectrometer (SIS) on the Advanced Composition Explorer(ACE) have measured energy spectra of cosmic-ray elements and isotopes since launch in 1997. We report energy spectra of abundant elements from C to Ni during solar minimum conditions from the 1997, 2009, and 2019-2020 solar minima and compare peak intensities with solar-wind conditions in these 3 minima. In 2010 we reported that peak intensities from the 2009 solar minimum were the highest of the space era (coinciding with the weakest interplanetary magnetic field of the space era). During Nov.2019-January 2020 ACE data show 200 MeV/nuc intensities of C-Fe reached, and in some cases exceeded those in 2009.This talk reports GCR intensities from 1997-2021 and discusses their dependence on solar-wind properties.

Speaker: Dr Richard Mewaldt (California Institute of Technology)
• 225
SOLAR MODULATION OF GALACTIC-COSMIC RAY ANTIPROTONS

In recent years, several new measurements of the antiproton component of the cosmic radiation have become available. These measurements have improved significantly the existing statistics, extending the explored energy region from few tens of MeV up to hundreds of GeV. These measurements are particularly relevant to understand the propagation of cosmic rays in the Galaxy and in the investigation of the nature of Dark Matter. However, an unambiguous interpretation of the experimental data requires a proper reconstruction of the very Local Interstellar Spectrum (LIS) of cosmic-ray antiprotons. Since these measurements are performed deep inside the heliosphere, solar modulation as a highly time and space dependent process which follows the 11-year solar activity cycle, has to be taken into account appropriately. In this work, using a 3D state-of-art solar modulation model, a new LIS for cosmic-ray antiprotons and its related uncertainties are presented. This LIS is derived to match, when modulated, the data sets from AMS02, PAMELA and BESS.

Speaker: Riccardo Munini
• 226
Study Galactic Cosmic Ray Modulation with AMS-02 observation

The accurate measurements of the galactic cosmic ray (GCR) fluxes as function of time and energy by the Alpha Magnetic Spectrometer (AMS) give us unique information to search dark matter, to study the dynamics of solar modulation, to constraint the parameters in modulation model, to improve the precision of radiation dose prediction in the ongoing deep space exploration.
The transport of low rigidity GCRs (<30GV) in the heliosphere is described by the Parker equation. This equation is solved by stochastic differential equation approach in numerical model. The input parameters in the model (solar wind speed, tilt angle, magnetic intensity and polarity) are obtained by the observation near the Earth. The time varying parameters (diffusion coefficient, drift coefficient) is usually tuned manually. This method only gives result what looks good, but cannot gives the uncertainty of parameters.
In this study, the Markov chain Monte Carlo (MCMC) technique is used to determine the time varying posterior probability distribution of parameters related to the GCR transport equation. In Bayesian statistics, MCMC is a class of samplers in which we can simulate draws that are slightly dependent and are approximately from a posterior distribution. The Metropolis-Hastings algorithm is used to implement the MCMC sampler. Compared to the traditional method where the likelihood function is evaluated on the grid of points in parameter space, the MCMC sampler is low resource consumption as it is insensitive to the dimensionality of the parameter space.

Speaker: xiaojian song (Shandong Institute of advanced technology)
• Discussion: 34 Radio Detection of Neutrinos | NU 05

#### 05

• 227
Sensitivity of a radio array embedded in a deep Gen2-like optical array.

Speaker: Abby Bishop
• 228

The Askaryan Radio Array (ARA) is a ground-based radio detector at the South Pole designed to capture Askaryan emission from ultra-high energy neutrinos interacting within the Antarctic ice. The newest ARA station has been equipped with a phased array trigger, in which radio signals in multiple antennas are summed in predetermined directions prior to the trigger. In this way, impulsive signals add coherently, while noise likely does not, allowing the trigger threshold to be lower than a traditional ARA station. In this talk, I will discuss our ability to analyze these low-threshold events, using data from the 2019 season to illustrate new analysis techniques that yield high efficiency for low-SNR signals. I will also discuss how these analysis techniques could be applied to next-generation radio detectors.

Speaker: Kaeli Hughes (The University of Chicago)
• 229
Hardware Development for the Radio Neutrino Observatory in Greenland (RNO-G)

The Radio Neutrino Observatory in Greenland (RNO-G) is designed to make the first observations of ultra-high energy neutrinos at energies above 10 PeV, playing a unique role in multi-messenger astrophysics as the world's largest in-ice Askaryan radio detection array. The experiment will be composed of 35 autonomous stations deployed over a 5 x 6 km grid near NSF Summit Station in Greenland. The electronics chain of each station is optimized for sensitivity and low power, incorporating 100 - 600 MHz RF antennas at both the surface and in ice boreholes, low-noise amplifiers, custom RF-over-fiber systems, and an FPGA-based phased array trigger. Each station will operate at 25 W, allowing for a live time of ~70% from a solar power system. The communications system is composed of a high-bandwidth LTE network and an ultra-low power LoRaWAN network. I will also present on the calibration and DAQ systems, as well as status of the first deployment of 10 stations in Summer 2021.

Speaker: Daniel Smith (University of Chicago)
• 230
Improving Radio Frequency Detectors using High Performance Programmable Logic Devices

An increasing number of experiments are targeting GHz bandwidth impulsive radiation induced by high energy neutrinos in ice or high energy cosmic ray air showers. Beamforming triggers improve detection prospects at low signal-to-noise ratio (SNR), since effective SNR scales as the square root of the number of phased array antennas in a coherent sum. However, this also brings high technological requirements with an increasing number of narrower beams required, while sub-nanosecond synchronisation must be maintained across the antennas summed in each beam. A prototype digital beamforming trigger is developed using Radio-frequency-systems-on-a-chip (RFSoCs), an adaptable radio platform leveraging the advantages of Field Programmable Gate Arrays (FPGAs). Findings are presented including power consumption, number of beams that can be formed per chip, trade-offs between resource usage and trigger efficiency and using programmable logic for flexible digital filtering capabilities.

Speaker: Cheng Xie (University College London)
• 231
Effects of raytracing on neutrino simulations using RadioPropa

The in-ice radio detection of the radio signals caused by the interaction of high energy neutrinos in vast natural media like polar ice, will be a promising technique to detect neutrinos of energies beyond the ones thus far measured. Because of the large attenuation length in ice for radio O(1km), sparse arrays can be built implying large effective volumes.

The simulations of effective volume calculations and reconstructions of the waveforms highly depend on the ice modelling. Thus far, for simplification, mainly analytically solvable exponential models of the ice are used. This allows for computationally fast raytracing. More elaborate methods, like FDTD (solving Maxwell equations on a full grid) can incorporate all ice properties. In particular, allowing for rays to reflect within the ice due to density discontinuities or allowing rays to travel horizontally through the firn (upper 200 m). However, this method is due to its heavy computing load impractical for large-scale simulations and reconstructions.

RadioPropa is a numerical ray-tracer that was started to accommodate more complex ice models with acceptable speed. It is forked from the cosmic ray propagation code CRPropa. Presented here are waveform simulations and reconstructions (with respectively NuRadioMC and NuRadioReco) using RadioPropa. This contribution shows the effects of a non-exponential ice-model on the radio waveforms and the implications for reconstruction. Also, the implementation of horizontal propagation due to a non-smooth ice-model and its effect on the neutrino waveforms are shown.

Speaker: Mr Bob Oeyen (Ghent University)
• 232
Broadband RF Phased Array Design for UHE neutrino detection

Phased array radio-frequency (RF) systems have a wide variety of applications in engineering and physics research. Phased array designs are proposed as a trigger system for Askaryan-class in-situ ultra-high energy (UHE) neutrino detectors. Located in Antarctica, these detectors will record RF pulses generated by UHE neutrinos via the Askaryan effect. Modelling the response of phased arrays is straightforward in an environment with uniform index of refraction. However, some detector designs call for phased array deployment at depths where the index of refraction is changing. One solution for computing the response of phased arrays in such an environment is computational electromagnetics with the finite difference time-domain method (FDTD). Using the open-source MIT Electrogmagnetic Equation Propagation (MEEP) package, a set of phased array designs are presented and compared to theoretical expectations. Precise matches between MEEP simulation and radiation pattern predictions at different frequencies and beam angles are demonstrated. Given that the computations match the theory, the effect of embedding a phased array within a medium of varying index of refraction is then studied. Understanding the effect of varying index on phased arrays is critical for proposed UHE neutrino observatories which rely on phased arrays embedded in natural ice. Future work will develop phased array concepts with parallel MEEP for speed and complexity enhancements that account for the 3D shape of proposed dipole antennas proposed as the physical RF elements for in-situ detectors.

Speaker: Jordan Hanson (Whittier College)
• 233

High-energy neutrinos with energies above a few $10^{16}~$eV can be measured efficiently with in-ice radio detectors which complement optical detectors such as IceCube at higher energies. Several pilot arrays explore the radio technology successfully in Antarctica. Because of the low flux and interaction cross-section of neutrinos it is vital to increase the sensitivity of the radio detector as much as possible. In this manuscript, different approaches to trigger on high-energy neutrinos are systematically studied and optimized. We find that the sensitivity can be improved substantially (by more than 50% between $10^{17}~$eV and $10^{18}~$eV) by simply restricting the bandwidth in the trigger to frequencies between 80 and 200 MHz instead of the currently used 80 to $1~$GHz bandwidth. We also compare different trigger schemes that are currently being used (a simple amplitude threshold, a high/low threshold trigger and a power-integration trigger) and find that the scheme that performs best depends on the dispersion of the detector. These findings inform the detector design of future Askaryan detectors and can be used to increase the sensitivity to high-energy neutrinos significantly without any additional costs. The findings also apply to the phased array trigger concept.

Speaker: Christian Glaser (Uppsala University, Sweden)
• 234
A novel trigger based on neural networks for radio neutrino detectors

The ARIANNA experiment is a proposed Askaryan detector designed to record radio signals induced by neutrino interactions in the Antarctic ice. Because of the low neutrino flux at high energies, the physics output is limited by statistics. Hence, an increase in sensitivity will significantly improve the interpretation of data and will allow us to probe new parameter spaces. The trigger thresholds are limited by the rate of triggering on unavoidable thermal noise fluctuations. Here, we present a real-time thermal noise rejection algorithm that will allow us to lower the thresholds substantially and increase the sensitivity by up to a factor of two compared to the current ARIANNA capabilities. A deep learning discriminator, based on a Convolutional Neural Network (CNN), was implemented to identify and remove a high percentage of thermal events in real time while retaining most of the neutrino signal. We describe a CNN that runs efficiently on the current ARIANNA microcomputer and retains 94% of the neutrino signal at a thermal rejection factor of $10^5$. Finally, we report on the experimental verification from lab measurements.

Speaker: Astrid Anker
• 235

The Askaryan Radio Array (ARA) is a gigaton size neutrino radio telescope located at the near geographic South Pole. ARA has five independent stations designed to detect Askaryan emission coming from the interaction between ultra-high energy neutrinos ( > 10 PeV ) and Antarctic ice. Each station corresponds of 16 antenna clusters deployed in a matrix shape under ~200 m deep in the ice. The simulated neutrino template, including the detector response model, was implemented as a new search technique for reducing background noise and increasing the vertex reconstruction resolution. The template is designed to scan through the data by the matched filter method, inspired by LIGO, looking for a low SNR neutrino signature and ultimately aiming to lower the detector's energy threshold. I will present the estimated sensitivity improvements to ARA analyses through the application of the template technique with results from simulation and data.

Speaker: Myoungchul Kim (Chiba University)
• 236
Application of parabolic equation methods to in-ice radiowave propagation for ultra high energy neutrino detection experiments

Many ultra high energy neutrino detection experiments seek radiowave signals from neutrino interactions deep within polar ice, and an understanding of in-ice radiowave propagation is therefore of critical importance. The parabolic equation (PE) method for modeling the propagation of radio waves is a suitable intermediate between ray tracing and finite-difference time domain (FDTD) methods in terms of accuracy and computation time. The RET collaboration has developed the first modification of the PE method for use in modeling in-ice radiowave propagation for ultra high energy cosmic ray and neutrino detection experiments. In this presentation we will detail the motivation for the development of this technique, the process by which it was modified for in-ice use, and showcase the accuracy of its results by comparing to FDTD and ray tracing.

Speaker: Cade Sbrocco (The Ohio State University)
• 237
Capabilities of the ARIANNA Neutrino Pointing Resolution, with Implications for Future Ultra-high Energy Neutrino Astronomy

We describe a radio-frequency polarization measurement by the ARIANNA surface station using a residual hole from the South Pole Ice Core (SPICEcore) Project. Radio pulses were emitted from a transmitter located down to 1.7 km below the snow surface. After deconvolving the raw signals for the detector response and attenuation from propagation through the ice, the signal pulses show no significant distortion and agree with a reference measurement of the emitter made in an anechoic chamber. The direction to transmitted radio pulse was measured with an angular resolution of 0.37 degree [statistical error]. For polarization, the statistical error of the polarization vector is depth dependent and below 1 degree. In addition, a slow systematic error as a function of depth is 2.7 degrees. Neither the direction or polarization measurement show a significant offset as a function of depth relative to expectation.

We also report the on the results of a simulation study of the ARIANNA neutrino direction and energy resolution. The software tool NuRadioMC was used to reconstruct the polarization and viewing angle to determine the neutrino direction. Multiple models of Askaryan radiation and detector sites along with a range of neutrino energies were tested. The neutrino space angle resolution was determined to be below 3 degrees, which is comparable to the systematic polarization uncertainty. Therefore it is expected that the polarization resolution, which is the dominant contribution to the neutrino space angle resolution, will be improved in future studies by determining and eliminating systematic effects. Finally, the fractional neutrino energy resolution is reported at 0.25, which is below the inelasticity limit.

Speaker: Steven Barwick (University of California Irvine)
• 238
Deep learning reconstruction of the neutrino energy with a shallow Askaryan detector

Cost effective in-ice radio detection of neutrinos above a few $10^{16}~$eV has been explored successfully in pilot-arrays. A large radio detector is currently being constructed in Greenland with the potential to measure the first cosmogenic neutrino, and an order-of-magnitude more sensitive detector is being planned with IceCube-Gen2. We present the first end-to-end reconstruction of the neutrino energy from radio detector data. NuRadioMC was used to create a large data set of 40 million events of expected radio signals that are generated via the Askaryan effect following a neutrino interaction in the ice for a broad range of neutrino energies between 100PeV and 10EeV. We simulated the voltage traces that would be measured by the five antennas of a shallow detector station in the presence of noise. We trained a deep neural network to determine the shower energy directly from the simulated experimental data and achieve a resolution better than a factor of two (STD <0.3 in $\log_{10}(E)$) which is below the irreducible uncertainty from inelasticity fluctuations. We present the model architecture and discuss the generalizability of the model in the presence of systematic uncertainties in the simulation code. This method will enable Askaryan detectors to measure the neutrino energy.

Speaker: Christian Glaser (Uppsala University, Sweden)
• 239
Direction reconstruction for the Radio Neutrino Observatory Greenland

The Radio Neutrino Observatory Greenland (RNO-G) is planned to be the first large-scale implementation of the in-ice radio detection technique. It targets astrophysical as well as cosmogenic neutrinos with energies above 10 PeV. The deep component of a single RNO-G station consists of three strings with antennas to capture horizontal as well as vertical polarization. This contribution shows a model-based approach to reconstruct the direction of the neutrinos with an RNO-G station. The timing of the waveforms is used to reconstruct the vertex position and the shape and amplitude of the waveform are used to reconstruct the viewing angle as well as the polarization, which will add up to the zenith and azimuth direction of the neutrino. We present the achieved angular resolution and discuss implications for the science of RNO-G.

Speaker: Ms Ilse Plaisier (DESY, Zeuthen)
• 240
Discovering the Highest Energy Neutrinos with the Payload for Ultrahigh Energy Observations (PUEO)

The Payload for Ultrahigh Energy Observations (PUEO) is a NASA Long-Duration Balloon Mission that has been selected for concept development. PUEO have unprecedented sensitivity to ultra-high energy neutrinos above 10^18 eV. PUEO will be sensitive to both Askaryan emission from neutrino-induced cascades in Antarctic ice and geomagnetic emission from upward-going air showers that are a result of tau neutrino interactions. PUEO is also especially well-suited for point source and transient searches. Compared to its predecessor ANITA, PUEO achieves better than an order-of-magnitude improvement in sensitivity and lowers the energy threshold for detection, by implementing a coherent phased array trigger, adding more channels, optimizing the detection bandwidth, and implementing real-time filtering. I will discuss the science reach and plans for PUEO, leading up to a 2024 launch.

Speaker: Abigail Vieregg (University of Chicago)
• 241
Evolving Antennas for Ultra-High Energy Neutrino Detection

Evolutionary algorithms are a type of artificial intelligence that utilize principles of evolution to efficiently determine solutions to defined problems. These algorithms are particularly powerful at finding solutions that are too complex to solve with traditional techniques and at improving solutions found with simplified methods. The GENETIS collaboration is developing genetic algorithms (GAs) to design antennas that are more sensitive to ultra-high energy neutrino-induced radio pulses than current detectors. Improving antenna sensitivity is critical because UHE neutrinos are extremely rare and require massive detector volumes with stations dispersed over hundreds of km2. The GENETIS algorithm evolves antenna designs using simulated neutrino sensitivity as a measure of fitness by integrating with XFdtd, a finite-difference time-domain modeling program, and with simulations of neutrino experiments. The best antennas will then be deployed at the RNO-G experiment in Greenland for initial testing. The GA is predicted to create antennas that improve on the designs used in the existing ARA experiment by more than a factor of 2 in neutrino sensitivities. This research could improve antenna sensitivities in future experiments and thus accelerate the discovery of UHE neutrinos. This is the first time that antennas have been designed using GAs with a fitness score based on a physics outcome, which will motivate the continued use of GA-designed instrumentation in astrophysics and beyond. This proceeding will report on advancements to the algorithm, steps taken to improve the GA performance, the latest results from our evolutions, and the manufacturing roadmap.

Speaker: Julie Rolla (Ohio State Univerisity)
• 242
Neutrino direction and flavor-id reconstruction from radio detector data using deep learning

With the construction of RNO-G and plans for IceCube-Gen2, neutrino astronomy at EeV energies is at the horizon for the next years. Here, we determine the neutrino pointing capabilities and explore the sensitivity to the neutrino flavor for an array of shallow radio detector stations. The usage of deep learning for event reconstruction is enabled through recent advances in simulation codes that allow the simulation of realistic training data sets. A large data set of expected radio signals for a broad range of neutrino energies between 100 PeV and 10 EeV is simulated using NuRadioMC. A deep neural network is trained on this low-level data and we find a direction resolution of a few degrees for all triggered events. We present the model architecture, how we optimized the model, and how robust the model is against systematic uncertainties. Furthermore, we explore the capabilities of a radio neutrino detector to determine the flavor id.

Speaker: Mr Sigfrid Stjärnholm (Uppsala University, Sweden)
• 243
Polarization Reconstruction of Cosmic Rays with the ARIANNA Neutrino Radio Detector

The ARIANNA detector is designed to detect neutrinos of energies above $10^{16} eV$. Due to the similarity in generated radio signals, cosmic rays are often used as test beams for neutrino detectors. Some ARIANNA detector stations are equipped with antennas capable of detecting air showers. The radio emission properties of air showers are well understood, and the polarization of the radio signal can be predicted from arrival direction with high precision. For this reason, cosmic rays can be used as a proxy to assess the reconstruction capabilities of the ARIANNA neutrino detector. We report on dedicated efforts of reconstructing the polarization of cosmic-ray radio pulses. A total of 245 cosmic rays are identified from over 90,000 triggered events collected between Dec 1, 2018 and Mar 15, 2019. A cut was put on these events requiring them to have a signal-to-noise (SNR) ratio of at least 5 in all upward-facing channels. Polarization of these cosmic rays were reconstructed with a resolution of 4 degrees (68% containment), which agrees with the expected value we obtained from simulation.

Speaker: Mr Leshan Zhao
• 244
Science case and detector concept for ARIANNA high energy neutrino telescope at Moore's Bay, Antarctica

The proposed ARIANNA neutrino detector, located at sea-level on the Ross Ice Shelf, Antarctica, consists of 200 autonomous and independent detector stations separated by 1 kilometer in a uniform triangular mesh. The primary science mission of ARIANNA is to search for sources of neutrinos with energies greater than 100 PeV, complementing the reach of IceCube. An ARIANNA observation of a neutrino source would provide strong insight into the enigmatic sources of cosmic rays. ARIANNA observes the radio emission from high energy neutrino interactions in the Antarctic ice. Among radio based concepts under current investigation, ARIANNA would uniquely survey the vast majority of the southern sky at any instant in time, and an important region of the northern sky, by virtue of its location on the surface of the Ross Ice Shelf in Antarctica. The broad sky coverage is specific to the Moore's Bay site, and makes the ARIANNA surface-based technology ideally suited to contribute to the multi-messenger thrust by the US National Science Foundation, Windows on the Universe – Multi-Messenger Astrophysics, providing capabilities to observe sources that vary strongly over time. The ARIANNA architecture is designed to measure the angular direction to 3 degrees and shower energy to 25% for every neutrino candidate. These high quality neutrino events are expected to play important role in the pursuit of multi-messenger observations of astrophysical sources. The surface-based architecture serves to inform future projects of much larger scale, such as the IceCube-Gen2 project.

Speaker: Steven Barwick (University of California Irvine)
• 245
Sensitivity studies for the IceCube-Gen2 radio array

The IceCube Neutrino Observatory at the South Pole has measured the diffuse astrophysical neutrino flux up to ~PeV energies and is starting to identify first point source candidates.
The next generation facility, IceCube-Gen2, aims at extending the accessible energy range to EeV in order to measure the continuation of the measured astrophysical spectrum, to identify neutrino sources, and to search for a cosmogenic neutrino flux. As part of IceCube-Gen2, a radio array is foreseen that is sensitive to detect Askaryan emission of neutrinos beyond ~5 PeV. Surface and deep antenna stations have different benefits in terms of effective area, resolution, and the capability to reject backgrounds from cosmic-ray air showers and may be combined to reach best sensitivity. The optimal detector configuration is still to be identified.

This contribution presents the full-array simulation efforts for a combination of deep and surface antennas, and compares different design options with respect to their sensitivity to fulfill the science goals of IceCube-Gen2.

• 246
The Calibration of the Geometry and Antenna Delay in Askaryan Radio Array Station 4 and 5

The Askaryan Radio Array (ARA) at the South Pole is designed to detect the radio signals produced by ultra high-energy cosmic neutrino interactions in the ice. There are 5 independent ARA stations, one of which (ARA5) includes a low-threshold phased array trigger string. The Data Acquisition System in all ARA stations is equipped with the Ice Ray Sampler second generation (IRS2) chip, a custom-made, application-specific integrated circuit (ASIC) for high-speed sampling and digitisation. In this contribution, we describe the methodology used to calibrate the IRS2 chip and the geometry namely the relative timing between antennas and their geometrical positions, for ARA stations 4 and 5. Our calibration allows for proper timing correlations between incoming signals, which is crucial for radio vertex reconstruction and thus detection of ultra high-energy neutrinos. With this methodology, we achieve a signal timing precision on a sub-nanosecond level and an antenna position precision within 10 cm.

Speaker: Dr Paramita Dasgupta (Post Doctoral Fellow at the Université libre de Bruxelles, Brussels)
• 247
The Giant Radio Array for Neutrino Detection (GRAND) project

The GRAND project aims to detect ultra-high-energy neutrinos, cosmic rays and gamma rays, with an array of 200,000 radio antennas over 200,000 km2, split into ~20 sub-arrays of ~10,000 km2 deployed worldwide. The strategy of GRAND is to detect air showers above 10^17 eV that are induced by the interaction of ultra-high-energy particles in the atmosphere or in the Earth crust, through its associated coherent radio-emission in the 50-200 MHz range. In its final configuration, GRAND plans to reach a neutrino-sensitivity of ~10^{-10} GeV cm^-2 s^-1 sr^-1 above 5x10^{17} eV combined with a sub-degree angular resolution. GRANDProto300, the 300-antenna pathfinder array, is planned to start data taking in 2021. It aims at demonstrating autonomous radio detection of inclined air-showers, and study cosmic rays around the transition between Galactic and extra-Galactic sources. We present preliminary designs and simulation results, plans for the ongoing, staged approach to construction, and the rich research program made possible by the proposed sensitivity and angular resolution.

Speaker: Kumiko Kotera (Institut d'Astrophysique de Paris)
• Discussion: 55 Ultra-High-Energy Gamma-Ray Sources and PeVatrons | GAI 04

#### 04

• 248
Discovery of 100 TeV gamma-rays from HESS J1702-420: a new PeVatron candidate

The identification of active PeVatrons, hadronic particle accelerators reaching the knee of the cosmic-ray spectrum (at the energy of few PeV), is crucial to understand the origin of cosmic rays in the Galaxy. In this context, we report on new H.E.S.S. observations of the PeVatron candidate HESS J1702-420, which reveal the presence of gamma-rays up to 100 TeV. This is the first time in the history of H.E.S.S. that photons with such high energy are clearly detected. Remarkably, the new deep observations allowed the discovery of a new gamma-ray source component, called HESS J1702-420A, that was previously hidden under the bulk emission traditionally associated with HESSJ1702-420. This new object has a power-law spectral slope < 2 and a gamma-ray spectrum that, extending with no sign of curvature up to 100 TeV, makes it an excellent candidate site for the presence of PeV-energy cosmic rays. This discovery brings new information to the ongoing debate on the nature of the unidentified source HESSJ1702-420, one of the most compelling PeVatron candidates in the gamma-ray sky, and on the origin of Galactic cosmic rays.

Speaker: Luca Giunti
• 249
Resolving the origin of very-high-energy gamma-ray emission from the PeVatron candidate SNR G106.3+2.7 using MAGIC telescopes

The supernova remnant (SNR) G106.3+2.7 is associated with a 100 TeV gamma-ray source reported by HAWC and is thus a promising PeVatron candidate. However, because of the poor angular resolution of HAWC, it is difficult to pinpoint the origin of the 100 TeV source. Because the SNR contains an energetic pulsar wind nebula (PWN) dubbed Boomerang and powered by the pulsar PSR J2229+6114, it is unclear whether the gamma-ray emission originates from the SNR or PWN complex and whether it is caused by hadronic or leptonic processes. We observed gamma rays above 200 GeV in the vicinity of the SNR G106.3+2.7 using the MAGIC telescopes for ~120 hours in total between May 2017 and August 2019, with an angular resolution of 0.07 – 0.1 degrees, which is unprecedented for this object at these energies. An extended gamma-ray emission spatially correlated with the radio continuum emission at the head and tail of SNR G106.3+2.7 was detected using the MAGIC telescopes. We find a hint of gamma-ray emission above 10 TeV only from the SNR tail region, while no significant emission above 5 TeV is found at the SNR head region containing the Boomerang PWN. Therefore, the gamma rays above 35 TeV detected with the air shower experiments are, likely, mainly emitted from the SNR tail region. In this presentation we discuss the morphology of the gamma-ray emission from this complex region and attempt self-consistent multiwavelength modeling of the energy spectrum from the different sources inside it.

Speaker: Tomohiko Oka (Kyoto University)
• 250
Predictions for gamma-rays from clouds associated with supernova remnant PeVatrons

Interstellar clouds can act as target material for hadronic cosmic rays; gamma-rays produced through inelastic proton-proton collisions and spatially associated with the clouds can provide a key indicator of efficient particle acceleration.
However, even for PeVatron sources reaching PeV energies, the system of cloud and accelerator must fulfil a several conditions in order to produce a detectable gamma-ray flux.
In this contribution, we characterise the necessary properties of both cloud and accelerator.
Using available Supernova Remnant (SNR) and interstellar cloud catalogues, and assuming particle acceleration to PeV energies in a nearby SNR, we produce a ranked shortlist of the most promising target systems, for which a detectable gamma-ray flux is predicted.
We discuss detection prospects for future facilities including CTA, LHAASO and SWGO; and compare our predictions with known gamma-ray sources.
A range of model scenarios are tested, including variation in the diffusion coefficient and particle spectrum, under which the best candidate clouds in our shortlist are consistently bright.
On average, a detectable gamma-ray flux is more likely for more massive clouds; systems with lower separation distance between the SNR and cloud; and for slightly older SNRs.

Speaker: Alison Mitchell (ETH Zurich)
• 251
Carpet-2 observation of E>300 TeV photons accompanying a 150-TeV neutrino from the Cygnus Cocoon

We report on the observation of an excess of E>300 TeV gamma-ray candidate events in temporal and spatial coincidence with the IceCube high-energy neutrino alert consistent with the origin in the Cygnus Cocoon. The Cygnus Cocoon is a prospective Galactic source of high-energy neutrinos and photons. The observations have been performed with Carpet-2, a surface air-shower detector equipped with a large-area muon detector at the Baksan Neutrino Observatory in the Northern Caucasus.

Speaker: Mr Viktor Romanenko (Institute for Nuclear Research of the Russian Academy of Sciences)
• 252
HAWC J2227+610: a potential PeVatron candidate for the CTA in the northern hemisphere

Recent observations of VER J2227+608 and the associated supernova
remnant G106.3+2.7 by the High Altitude Water Cherenkov (HAWC)
observatory confirm the special interest of this source as a Galactic Pe-
Vatron candidate in the northern hemisphere. HAWC J2227+610 emits
VHE gamma-ray emission, above 100 TeV, from a region coincident with
molecular clouds and shows a hard energy spectrum without clear cutoff.
This has induced several authors to suggest or claim a potential hadronic
origin for its gamma-ray emission. CTA could play a crucial role to under-
stand the particle acceleration mechanisms behind this source thanks to
its improved sensitivity with respect to the present IACT generation. The
purpose of this work is to investigate the potentiality of CTA to observe
HAWC J2227+610 and to disentangle the different suggested scenarios
of hadronic and leptonic emission. In particular we study the capability
in resolving the morphology of this source and its eventual energy de-
pendence taking advantage of the unprecedent angular resolution. The
study is based on simulations; the CTA prototype science tool gammapy
is employed.

Speaker: Gaia Verna
• 253
Gamma-ray Observation of SNR G106.3+2.7 with the Tibet Air Shower Array

We have been observing cosmic rays and gamma rays above TeV energies with an air shower (AS) array located in Tibet, China at an altitude of 4,300 m and in operation since 1990. In 2014 we added to the air shower array an underground muon detector (MD) array that enables us to observe gamma-ray-induced air showers with far better sensitivity than before, suppressing background cosmic-ray events by counting the number of muons contained in air showers. The background rejection power is typically estimated at 99.9% above 100 TeV. In this presentation, we report the observation of very-high-energy gamma-ray emissions from supernova remnant G106.3+2.7 using the data taken by the Tibet AS array and the MD array.

Speaker: Munehiro OHNISHI (ICRR, University of Tokyo)
• 1:30 PM
Break
• Plenary: Review 02 01

#### 01

Convener: Manfred Lindner (Max-Planck-Institut für Kernphysik)
• 254
Dark Matter: Knowns and Unknowns

: I will give an overview of the landscape of possible scenarios for dark matter, including a discussion of current constraints and some future directions for the field. I will comment on the status of several claimed anomalies, their possible relationships to dark matter physics, and alternative explanations.

Speaker: Tracy Slatyer
• 255
Probing particle acceleration through gamma-ray Solar flare observations

High-energy solar flares have shown to have at least two distinct phases: prompt-impulsive and delayed-gradual. Identifying the mechanism responsible for accelerating the electrons and ions and the site at which it occurs during these two phases is one of the outstanding questions in solar physics. Many advances have been made over the past decade thanks to new observational data and refined simulations that together help to shed light on this topic. For example, the detection by Fermi Large Area Telescope (LAT) of GeV emission from solar flares originating from behind the visible solar limb and >100 MeV emission lasting for more than 20 hours have suggested the need for a spatially extended source of acceleration during the delayed emission phase. In this talk I will review some of the major results from Fermi LAT observations of the 24th solar cycle and how this new observational channel combined with observations from across the electromagnetic spectrum can provide a unique opportunity to diagnose the mechanisms of high-energy emission and particle acceleration in solar flares.

Speaker: Melissa Pesce-Rollins ( )
• 3:30 PM
Break
• Plenary: Highlight 03 01

#### 01

Convener: Dr Markus Roth (KIT)
• 256
Highlights from direct dark matter detection

Direct detection experiments search for dark matter-induced signals in Earth-based detectors. I will present a short review on the current status and future of the field and will concentrate on selected results on the direct search for WIMPs, axions and beyond

Speaker: Marc Schumann (Univertity of Freiburg)
• 257
Highlights from the Telescope Array experiment

The Telescope Array (TA) is the largest cosmic ray observatory in the Northern Hemisphere. It is designed to measure the properties of cosmic rays over a wide range of energies. TA with it's low energy extension (TALE) observe cosmic ray induced extensive air showers between 2x10^15 and 2x10^20eV in hybrid mode using multiple instruments, including an array of scintillator detectors at the Earth's surface and telescopes to measure the fluorescence and Cerenkov light. The statistics at the highest energies are being enhanced with the ongoing construction of the TAx4 experiment which will quadruple the surface area of the detector. We review the present status of the experiments and most recent physics results on the cosmic ray anisotropy, chemical composition and energy spectrum. Notable highlights include a new feature in the energy spectrum at about 10^19.2 eV., and a new clustering of events in their arrival directions above this energy. We also report on a new spectrum and composition results in the lower energy range from the TALE extension.

Speaker: Grigory Rubtsov (Institute for Nuclear Research of the Russian Academy of Sciences)
• 258
Highlights from the Pierre Auger Observatory

tba

Speaker: Ralph Engel (Karlsruhe Institute of Technology (KIT))
• 5:30 PM
Break
• Discussion: 03 Muon Puzzle and EAS modeling | CRI 03

#### 03

• 259
Estimation of depth of maximum by relative muon content in air showers with energy greater than 5 EeV measured by the Yakutsk array

Characteristics of muons with a threshold $\varepsilon_{thr} \geq$ 1 GeV based on the air showers data in Yakutsk array were analyzed. Quantitative estimation of muons at different distance from the shower axis and the ratio of muon and charged particles at a distance of 600 m are obtained. An empirical relationship between the fraction of muons and longitudinal development – the depth of maximum development $X_{max}$ is found. Calculations of the muon fraction are performed using the QGSjetII-04 for different primary nuclei, and compared with experiment. Mass composition of primary particles induced air showers of highest energies is estimated from the muon component.

Speaker: Mr Igor Petrov (Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy)
• 260
A simulation study for one-pion exchange contribution on very forward neutron productions in ATLAS-LHCf common events

The mass composition is one of the key information to understand the origin of ultra-high energy cosmic rays. The interpretations of the mass composition from results by air shower experiments depend on hadronic interaction models used for the simulation. The uncertainties due to interaction models are reduced using recent experimental results at LHC.
However, due to no experimental results of pion-proton or pion-nucleus collisions at high energy, uncertainties remain in these collisions and it affects predictions of muon productions in air showers.
Recent results for very forward neutrons in pseudo-rapidity larger than 10.76 by the LHCf experiment show large differences from predictions by interaction models.
As a fundamental process of forward neutron production, the contribution of one pion exchange is proposed.
Though LHC can not circulate the pion beam, a virtual pion emitted from a proton in a proton beam can collide with a proton in the other proton beam.
In this work, we discuss a possibility to measure contributions from one-pion exchange on very forward neutrons using ATLAS and LHCf detectors in LHC RUN 3.
Expected energy resolution for neutrons and statistics in Run 3 are taken into account in the discussion. The prospect of measurements of one-pion exchange contributions is also presented.

Speaker: Ken Ohashi (Institute for Space-Earth Environmental Research, Nagoya Univ.)
• 261
Measurement of the Proton-Air Cross Section with Telescope Ar-rays Black Rock, Long Ridge, and Surface Array in Hybrid Mode.

Ultra High Energy Cosmic Ray (UHECR) detectors have been reporting on the proton-air cross section measurement beyond the capability of particle accelerators since 1984. The knowledge of this fundamental particle property is vital for our understanding of high energy particle interactions and could possibly hold the key to new physics. The data used in this work was collected over eight years using the hybrid events of Black Rock (BR) and Long Ridge (LR) fluorescence detectors as well as the Telescope Array Surface array Detector (TASD). The proton-air cross section is determined at √s= 73 TeV by fitting the exponential tail of the Xmax distribution of these events. The proton-air cross section is then inferred from the exponential tail fit and from the most updated high energy interaction models. σ inel p−air is observed to be 520.1±35.8 [Stat.]+25.3−42.9[Sys.] mb. This is the second proton-air cross section work reported by the Telescope Array collaboration.

Speaker: Rasha Abbasi (Loyola University Chicago-Physics Department)
• 262
Status and Prospects of the LHCf and RHICf experiments

Precise understanding of hadronic interactions at high energies is a key to improve chemical composition measurements of very high energy cosmic-rays and to solve the muon excess issue observed in high energy cosmic-ray experiments using air-shower technique. The LHCf and RHICf experiments measures the differential production cross sections of very forward neutral particle as photons, neutral pions and neutrons at LHC and RHIC, respectively. These data are critically important to test and tune hadronic interaction models used for air-shower simulations.

In this presentation, we introduce the recent results of both the experiments as well as our future operation plans. LHCf published an updated result of forward neutron measurement at pp, $\sqrt{s}$ = 13 TeV. From the observed neutron energy spectra, we also obtained the average inelasticity, which is one of the key parameters for air shower development, as 0.536 +0.031-0.037. In addition, several analysis are on-going; neutral pion measurement at $pp$, $\sqrt{s}$ = 13 TeV, central- forward correlation analysis with LHCf+ATLAS, photon measurement by RHICf.

LHCf plans to have operations at $pp$ and $p$O during the LHC-Run3 period. At $pp$ collisions, a new silicon readout system will be introduced to improve the read-out speed, and 10 times more statistics of the previous operation in 2015 will be obtained. Thanks to high statistics, rare particles such as $\eta$, $K^0_s$ and $\Lambda$ will be addressed also. We also plan another operation at RHIC in 2024 with a new detector. The detector, a calorimeter composed of tungsten, Si pad and pixel layers, will have a much wider acceptance and higher sensitivity of $K^0_s$ measurement than the current detector.

Speaker: Hiroaki Menjo (ISEE, Nagoya University)
• 263
Collective flow in ultra high energy cosmic rays within CORSIKA

In heavy ion collisions, the main goal is to create the quark-gluon plasma (QGP) and then study its properties in order to understand quantum chromodynamics at extreme conditions. Collective flow serves as an important probe to study the production and characterize the property of the QGP. In ultra high energy cosmic rays (UHECR), the collision energies are an order of magnitude higher than the current ion colliders. It is naturally to believe the QGP to be created in UHECR collisions. In this work, collective flow are analytically studied within CORSIKA model, with EPOS-LHC for high energy hadronic interaction. The collision energy dependence of collective flow will be also presented. These results will help the understanding of UHECR behavior and can be tested at China's large high altitude air shower observatory (LHAASO) experiments.

Speaker: Maowu Nie (Shandong University)
• 264
Muon number rescaling in simulations of air showers

The number of muons in extensive air showers predicted using LHC-tuned hadronic interaction models, such as EPOS-LHC and QGSJetII-04, is smaller than observed in showers recorded by leading cosmic rays experiments. In this paper, we present a new method to derive muon rescaling factors by analyzing reconstructions of simulated showers. The z-variable used (difference of initially simulated and reconstructed total signal in detectors) is connected to the muon signal and is roughly independent of the zenith angle but depends on the mass of primary cosmic ray. The performance of the method is tested by using Monte Carlo shower simulations for the hybrid detector of the Pierre Auger Observatory. Having an individual z-value from each simulated hybrid event, the corresponding signal at 1000 m, and using a parametrization of the muon fraction in simulated showers, we can calculate the multiplicative rescaling parameters of the muon signals in the ground detector even for an individual event, and study its dependence as a function of zenith angle and the mass of primary cosmic ray. This gives a possibility not only to test/calibrate the hadronic interaction models, but also to derive the beta exponent, describing an increase of the number of muons as a function of primary energy and cosmic-ray mass. Detailed simulations show dependence of beta on hadronic interaction properties, thus the determination of this parameter is important to understand the muon deficit problem.

Speaker: Dr Dariusz Gora (Institute of Nuclear Physics Polish Academy of Science)
• 265
Adjustments to Model Predictions of Depth of Shower Maximum and Signals at Ground Level using Hybrid Events of the Pierre Auger

'We present a new method to explore simple ad-hoc adjustments to the predictions of hadronic interaction models to improve their consistency with observed two-dimensional distributions of the depth of shower maximum, Xmax, and signal at ground level, as a function of zenith angle. The method relies on the assumption that the mass composition is the same at all zenith angles, while the atmospheric shower development and attenuation depend on composition in a correlated way. In the present work, for each of the three leading LHC-tuned hadronic interaction models, we allow a global shift ΔXmax of the predicted shower maximum, which is the same for every mass and energy, and a rescaling R_Had of the hadronic component at ground level which depends on the zenith angle.

We apply the analysis to 2297 events reconstructed by both fluorescence and surface detectors at the Pierre Auger Observatory with energies 10^18.5-10^19.0 eV. Given the modeling assumptions made in this analysis, the best fit reaches its optimum value when shifting the Xmax predictions of hadronic interaction models to deeper values and increasing the hadronic signal at both extreme zenith angles. The resulting change in the composition towards heavier primaries alleviates the previously identified model deficit in the hadronic signal (commonly called the muon deficit), but does not remove it. Because of the size of the required corrections ΔXmax and R_Had and the large number of events in the sample, the statistical significance of the corrections is large, greater than 5σ_stat even for the combination of experimental systematic shifts within 1σ_sys that are the most favorable for the models.

Speaker: Dr Jakub Vícha (Institute of Physics of Czech Academy of Sciences)
• 266
Air shower genealogy for muon production

Measurements of the muon content of extensive air showers at the highest energies show discrepancies compared to simulations as large as the differences between proton and iron. This so-called muon puzzle is commonly attributed to a lack of understanding of the hadronic interactions in the shower development. Furthermore, measurements of the fluctuations of muon numbers suggest that the discrepancy is likely a cumulative effect of interactions of all energies in the cascade.
A unique, novel feature of the air shower simulation code CORSIKA 8 allows us to access all previous generations of final-state muons up to the first interaction. With this technique, we study the influence of interactions happening at any intermediate stage in the cascade on muons depending on their energy and lateral distance in a quantitative way. We further relate our findings to recent and upcoming accelerator measurements and comment on the prospects of the proposed proton-oxygen run of the LHC.

Speaker: Maximilian Reininghaus (KIT / IAP)
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Density of GeV Muons Measured with IceTop

We present a measurement of the density of GeV muons in near-vertical air showers using three years of data recorded by the IceTop array at the South Pole. We derive the muon densities as functions of energy at reference distances of 600 m and 800 m for primary energies between 2.5 PeV and 40 PeV and between 9 PeV and 120 PeV, respectively. The measurements are consistent with the predicted muon densities obtained from Sibyll 2.1 assuming any physically reasonable cosmic ray flux model. However, comparison to the post-LHC models QGSJet-II.04 and EPOS-LHC shows that the post-LHC predict a higher muon density than Sibyll 2.1. Therefore, based on these models, the measured data yield lower average masses which are in tension with flux models obtained by fitting experimental data.

Speaker: Dennis Soldin (University of Delaware)
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Estimations of the muon content of cosmic ray air showers between 10 PeV and 1 EeV from KASCADE-Grande data

Measurements of KASCADE-Grande on the muon size in high energy extensive air showers (EAS) have provided evidence that the actual attenuation length of shower muons in the atmosphere is larger than the expectations from the hadronic interaction models QGSJET-II-04, EPOS-LHC and SIBYLL 2.3. This discrepancy is related to a deficient description of the shower muon content with atmospheric depth by MC models. To further explore the origin of the above anomaly, we have investigated the muon size as a function of the primary energy at different zenith angles using data from the KASCADE-Grande experiment. The procedure consisted in comparing the measured muon number flux against the predictions of a reference cosmic ray energy spectrum and from the observed difference to estimate the data/MC muon ratio that best describe the measurements. The ratio is then applied to the MC simulations and from here, we estimate the muon content versus the primary energy. As a reference model, we employed the energy spectrum measured from the Pierre Auger observatory, while, for the different cosmic ray abundances, the GSF model. Results are presented using the QGSJET-II-04, EPOS-LHC, SIBYLL 2.3 and SIBYLL 2.3c models in the analysis procedure.

Speaker: Juan Carlos Arteaga Velazquez (Universidad Michoacana de San Nicolas de Hidalgo)
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We present characteristics of hadronic cascades from interactions of cosmic rays in the atmosphere, simulated by the novel CORSIKA 8 framework. The simulated spectra of secondaries, such as pions, kaons, baryons and muons, are compared with cascade equations solvers CONEX and MCEq in air shower mode and full 3D air shower Monte Carlo simulations using the legacy CORSIKA 7 and AIRES. A novel capability of CORSIKA 8 is the simulation of cascades in media other than air, widening the scope of potential simulation applications. We demonstrate this capability by simulating cosmic ray showers in the Martian atmosphere. The CORSIKA 8 framework demonstrates good accuracy and robustness compared to previous results, in particular in those relevant for the production of muons in air showers. Furthermore, hyperons are studied as a messenger from high-density QCD and as an important precursor for high-energy secondaries, including neutrinos. It was also found that interactions of strange baryons can have non-negligible importance for cascade development that require extra care when using any such model in all contexts.

Speaker: Ralf Ulrich (Karlsruhe Institute of Technology)
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LHCf plan for proton-oxygen collisions at LHC

During LHC runs 1-2 the LHCf experiment measured neutral particles in the forward region of proton+proton and proton+lead ion collisions. These measurements allow the testing and fine tuning of hadronic interaction models in a phase space region relevant for studying the development of cosmic-ray air showers. One of the limitations in using the results obtained so far by LHCf is linked to the fact that the interactions of cosmic rays in the atmosphere involve low mass nuclei, mainly nitrogen and oxygen. Expectations for proton+nitrogen or proton+oxygen collisions can be obtained interpolating the results obtained with proton+proton and proton+lead collisions, but large uncertainties arise due to Ultra Peripheral Collisions occurring frequently in heavy ion interactions.
A new opportunity is under evaluation at the LHC, concerning the injection of oxygen ions in the LHC collider, as suggested in the past by the LHCf collaboration. Proton+oxygen collisions at the LHC energy scale would allow a direct study of atmospheric showers under controlled conditions. LHCf need a 2 nb^-1 integrated luminosity at low pile-up (mu<0.02) to complete a measurement at pseudorapidity larger than 8.4, for a total acquisition time of less than two days.
At the end of 2020 the cosmic-ray community has supported the LHCf proposal signing a letter to the LHC Committee to express the interest in the implementation of proton-oxygen collisions in the LHC run 3 and in the LHCf data taking.
We will present the LHCf plan and point of view in connection with this important opportunity at the LHC.

Speaker: Eugenio Berti (University of Florence)
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Measurement of muon contents in cosmic ray shower with LHAASO-KM2A around knee region

The number of muons observed at the ground from air showers is sensitive to the mass composition of cosmic ray. Large High Altitude Air Shower Observatory is a hybrid extensive air shower array and the KM2A is a sub-array covering an area of 1 km$^2$, consisting of electromagnetic detectors and muon detectors, can measure the muon content and shower size of the air shower simultaneously with high precision for cosmic rays in the knee region. The muon detector of the KM2A is the most powerful muon detector in the current cosmic ray observatory on the ground. In this paper, the experimental data is recorded by the KM2A in 2020. The mean number of muons in air shower is measured by analyzing the signal of muon detectors for the cosmic ray from hundreds of TeV to tens of PeV, where the energy is reconstructed with the shower size and muon number which is weakly dependent on the components of cosmic ray. We investigate the ability to identify cosmic ray components using muon content. Based on the constant intensity cut method, the muon attenuation length is derived by fitting the muon number with same flux in different zenith angle. The relation between attenuation length and muon number in the shower is studied also. In addition, the experiment data in muon abundance is compared with the simulation results of proton and iron. The mean logarithmic mass of the cosmic ray derived from the mean number of muons in same energy interval, together with the mean mass of supposed spectra, are presented with systematic errors from the energy scale and hadronic model.

Speaker: Dr Hengying Zhang (Shandong University)
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Measurements of the average muon energy in inclined muon bundles in the NEVOD-DECOR experiment

One of the first setups at which an excess of muons in comparison with the expectation (“muon puzzle”) was detected and its dependence on the primary energy was measured, was the NEVOD-DECOR complex. Since various mechanisms for the appearance of an excess of multi-muon events (of cosmophysical or nuclear-physical nature) should have different effects on the muon energy, one of the possible approaches to solving the problem is the studying of the energy characteristics of EAS muon component and their changes with the energy of particles of primary cosmic rays. The average energy loss of muons in matter almost linearly depends on the muon energy. If an excess of high energy muons appears, then this should be reflected in the dependence of the muon energy deposit on the primary energy. At present, such an experiment is being carried out at the NEVOD-DECOR setup. The installation includes a Cherenkov water calorimeter and a precise coordinate-tracking detector. The energy deposit of muon bundles is measured from the response of the NEVOD calorimeter, and the coordinate-tracking detector DECOR allows one to determine the number of muons in the bundles. For the first time, experimental estimates of the average muon energy in the bundles and its dependence on zenith angle and primary energy in the range from 10 PeV to 1000 PeV have been obtained and compared with the results of calculations performed using the CORSIKA-based simulation using modern models of hadronic interactions.

Speaker: E.A. Yurina (MEPhI)
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Measurements of the charge ratio and polarization of cosmic ray muons with the Super-Kamiokande detector

Cosmic ray muons arise from the showers of secondary particles produced in the interactions of primary cosmic particles with air nuclei at the top of the atmosphere. The interaction products, pions and kaons composing showers mostly decay to muons reflect the details of the hadronic interactions depending on their energy. Measurements of the charge ratio and polarization of cosmic ray muons can be used to constrain high energy hadronic interaction models in the atmosphere. Previous measurements have been performed in various experiments. Kamiokande measured the charge ratio and polarization as 1.37+/-0.06(stat)+/-0.01(syst) and 0.26+/-0.04(stat)+/-0.05(syst), respectively, at the sea level momentum of 1.2 TeV/c. In this presentation, we will report the current status of the measurement of the charge ratio and polarization using data collected by the Super-Kamiokande detector located at a depth of 2700 m of water equivalent.

Speaker: Hussain Kitagawa (Okayama University)
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The development of hadronic cascades in extensive air-showers is modeled by hadronic interaction models based on extrapolations of collider data. The models' predictions at the highest energies are at a known tension with the description of measurements of the muonic component if the mass composition derived from the fluorescence technique is assumed. We apply an ad-hoc modification to the CORSIKA Monte-Carlo generator that allows for adjustment of features of hadronic interactions such as multiplicity, elasticity and cross-section. Compared to similar previous studies, we are now able to obtain not only information related to the longitudinal development of the shower, such as the mean depth of shower maximum, but also information about the lateral distribution of particles. Moreover, we generate a scan across the various possible combined modifications of the Sibyll 2.3d model using both protons and iron nuclei, quantify their effects on both the lateral and longitudinal features of a cosmic-ray shower and identify regions of the modification phase space which are explaining, within the stated systematics, both the ground-based and fluorescence-based measurements of cosmic rays at the highest energies.

Speaker: Jiri Blazek (FZU Prague)
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Muon deficit in simulations of air showers inferred from AGASA data

Multiple experiments reported evidences of a muon deficit in air-shower simulations with respect to data, which increases with the primary energy. In this work, we study the muon deficit using measurements of the muon density at $1000\,$m from the shower axis obtained by the Akeno Giant Air Shower Array (AGASA). The selected events have reconstructed energies in the range $18.83\,\leq\,\log_{10}(E_{R}/\textrm{eV})\,\leq\,19.46$ and zenith angles $\theta\leq 36^\circ$. We compare these muon density measurements to proton, iron, and mixed composition scenarios, obtained by using the high-energy hadronic interaction models EPOS-LHC, QGSJetII-04, and Sibyll2.3c. We find that AGASA data are compatible with a heavier composition, lying above the predictions of the mixed composition scenarios. The average muon density divided by the energy in AGASA data is greater than in the mixed composition scenarios by a factor of $1.49\pm0.11\,\textrm{(stat)}\pm0.18\,\textrm{(syst)}$, $1.54\pm0.12\,\textrm{(stat)}\pm0.18\,\textrm{(syst)}$, and $1.66\pm0.13\,\textrm{(stat)}\pm0.20\,\textrm{(syst)}$ for EPOS-LHC, Sibyll2.3c, and QGSJetII-04, respectively. We interpret this as further evidence of a muon deficit in air-shower simulations at the highest energies.

Speaker: Flavia Gesualdi (Instituto de Tecnologías en Detección y Astropartículas (CNEA, CONICET, UNSAM), and Karlsruhe Institute of Technology, Institute for Astroparticle Physics)
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Muon excess in ultra-high energy inclined EAS according to the NEVOD-DECOR data

Data of the NEVOD-DECOR experiment on investigations of inclined cosmic ray muon bundles for a long time period (May 2012 – March 2021) are presented. Their comparison with the results of calculations based on simulations of EAS hadron and muon components allows one to study the behavior of the energy spectrum and mass composition of primary cosmic rays and/or to check the validity of hadron interaction models in a wide energy range from about 10^16 to more than 10^18 eV. The analysis showed that the observed intensity of muon bundles at primary particle energies of about 10^18 eV and higher can be compatible with the expectation only under the assumption of an extremely heavy mass composition of cosmic rays. This conclusion is consistent with data of a number of other experiments investigating the muon component of air showers at ultra-high energies. On the contrary, measurements of the depth of the shower maximum in the atmosphere (Xmax) in the experiments using air fluorescence technique favor a light mass composition of primary cosmic rays at these energies. This contradiction (so-called “muon puzzle”) cannot be resolved without serious changes of the existing hadron interaction models.

Speaker: R.P. Kokoulin (MEPhI)
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On the muon scale of air showers and its application to the AGASA data

Recently, several experiments reported a muon deficit in air-shower simulations with respect to the data. This problem can be studied using an estimator that quantifies the relative muon content of the data with respect to those of proton and iron Monte-Carlo air-shower simulations. We analyze two estimators. The first one, based on the logarithm of the mean of the muon content, is built from experimental considerations. It is ideal for comparing results from different experiments as it is independent of the detector resolution. The second estimator is based on the mean of the logarithm of the muon content, which implies that it depends on shower-to-shower fluctuations. It is linked to the mean-logarithmic mass $\langle \ln A \rangle$ through the Heitler-Matthews model. We study the properties of the estimators and their biases considering the knowns and unknowns of typical experiments. Furthermore, we study these effects in measurements of the muon density at $1000$ m from the shower axis obtained by the Akeno Giant Air Shower Array (AGASA). Finally, we report the estimates of the relative muon content of the AGASA data, which support a muon deficit in simulations. These estimates constitute valuable additional information of the muon content of air-showers at the highest energies.

Speaker: Flavia Gesualdi (Instituto de Tecnologías en Detección y Astropartículas (CNEA, CONICET, UNSAM), San Martín, Argentina, and Karlsruhe Institute of Technology, Institute for Astroparticle Physics (IAP), Karlsruhe, Germany)
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