14th AxionWIMP conference (Patras workshop)

17 Jun 2018, 15:00 → 22 Jun 2018, 16:00 Europe/Berlin

Auditorium (DESY in Hamburg)

The 14th Patras Workshop on Axions, WIMPs and WISPs will be held at DESY in Hamburg (Germany) from June 18 to 22, 2018.

This workshop is aiming to continue the rich and successful series, reviewing recent theoretical advances, laboratory experiments, novel ideas as well as astrophysical and cosmological results in the fields of axions, WIMPs and WISPs. Participation by young scientists is encouraged. To promote our exciting field among non-experts at DESY a "science slam" is scheduled and an award is foreseen. Applications to participate are welcome, see abstract submission (presentation type "science slam").

More details on the workshop are given on the conference webpage:
http://axion-wimp2018.desy.de/

Sunday 17 June

16:00 → 17:00 Registration

17:00 → 19:00 Reception

Monday 18 June

08:00 → 09:00 Registration

09:00 → 09:25 Opening

Convener: Prof. Konstantin Zioutas (CERN)

09:00 Welcome

Speaker: Dr Axel Lindner (DESY)

Slides Intro.pptx

09:05 Particle Physics at DESY

Speaker: Joachim Mnich (DESY)

Slides Patras-WS.Intro.v3.pdf Patras-WS.Intro.v3.pptx

09:25 → 10:00 ADMX: Recent results at the DFSZ frontier

The Axion Dark Matter eXperiment (ADMX) is conducting a search for axions trapped in the dark-matter halo of our Galaxy. ADMX employs a large-volume superconducting magnet, a high-Q tunable microwave cavity, an ultrasensitive SQUID microwave amplifier, and a high-performance dilution refrigerator to enable temperatures in the 80-200 mK range for cavity and SQUID. In the last year, this "Generation 2" ADMX detector has reached the sensitivity to detect axions even in the case where their coupling to two photons is as weak as the somewhat pessimistic DFSZ theory. The ADMX detector, located at the University of Washington, has completed its first run at this design sensitivity. There were no detections and the search continues with a second science run. The resulting limits on axion mass, the prospects for the ongoing search, and the outlook for the future will be discussed.

Speaker: David Tanner (University of Florida)

Slides Tanner-Patras18.pdf

10:00 → 11:00 Plenary presentations

Convener: Prof. Konstantin Zioutas (CERN)

10:00 Residual annihilations of asymmetric DM

Dark matter coupled to light mediators has been invoked to resolve the putative discrepancies between collisionless cold DM and galactic structure observations. However, $\gamma$-ray searches and the CMB strongly constrain such scenarios. To ease the tension, we consider asymmetric DM. We show that, contrary to the common lore, detectable annihilations occur even for large asymmetries, and derive bounds from the CMB, $\gamma$-ray, neutrino and antiproton searches. We then identify the viable space for self-interacting DM. Direct detection does not exclude this scenario, but provides a way to test it.

Speaker: Dr Iason Baldes (DESY)

Slides baldes.pdf

10:20 Axions and stars: bounds, hints and experimental potential

Stars are extremely powerful laboratories for light, weakly interacting particles. In this talk, I will give an overview of stellar bounds and hints on axions and axion like particles. In particular, I will review what we can learn from the evolution of white dwarfs, red giant and horizontal branch stars, and supernovae. I will discuss some new studies and recent advances on supernovae and red giant stars and show the hinted areas in the axion/ALP parameter space. Finally, I will consider the experimental potential to probe these areas, focusing not only on experiments sensitive to the axion-photon coupling (such as IAXO and ALPS) but to instruments sensitive to the axion coupling to other standard model fields. Some recent topics related to stellar axions, in particular their impact on the mass threshold for Carbon ignition or the problem of direct detection of supernova axions, will not be considered in this talk and will be discussed elsewhere in this workshop (see presentations by I. Dominguez and A. Mirizzi).

Speaker: Dr maurizio giannotti (Barry Universtiy)

Slides MGiannotti_Patras2018.pdf

10:40 New Probes for Ultra-Low-Mass Dark Matter

Ultra-low-mass bosonic dark matter particles produced after the Big Bang may form an oscillating classical field, which can be sought for in a variety of low-energy laboratory experiments based on spectroscopic, interferometric and magnetometric techniques, as well as in astrophysical phenomena. These bosonic particles can also mediate anomalous fifth forces between ordinary-matter particles. Recent measurements in atoms and astrophysical phenomena have already allowed us to improve on existing constraints on a broad range of non-gravitational interactions between dark bosons and ordinary-matter particles by many orders of magnitude (up to 15 orders of magnitude in the case of ultra-low-mass dark matter) [1-12]. Several other groups have recently reported new limits on ultra-low-mass dark matter from related measurements [13-17]. **References** [1] Y. V. Stadnik, V. V. Flambaum, *Phys. Rev. D* **89**, 043522 (2014). [2] B. M. Roberts, Y. V. Stadnik, V. A. Dzuba, V. V. Flambaum, N. Leefer, D. Budker, *Phys. Rev. Lett.* **113**, 081601 (2014). [3] B. M. Roberts, Y. V. Stadnik, V. A. Dzuba, V. V. Flambaum, N. Leefer, D. Budker, *Phys. Rev. D* **90**, 096005 (2014). [4] Y. V. Stadnik, V. V. Flambaum, *Phys. Rev. Lett.* **113**, 151301 (2014). [5] Y. V. Stadnik, V. V. Flambaum, *Phys. Rev. Lett.* **114**, 161301 (2015). [6] Y. V. Stadnik, V. V. Flambaum, *Phys. Rev. Lett.* **115**, 201301 (2015). [7] Y. V. Stadnik, V. V. Flambaum, *Phys. Rev. A* **93**, 063630 (2016). [8] Y. V. Stadnik, V. V. Flambaum, *Phys. Rev. A* **94**, 022111 (2016). [9] N. Leefer, A. Gerhardus, D. Budker, V. V. Flambaum, Y. V. Stadnik, *Phys. Rev. Lett.* **117**, 271601 (2016). [10] C. Abel *et al.* (nEDM collaboration), *Phys. Rev. X* **7**, 041034 (2017). [11] Y. V. Stadnik, V. A. Dzuba, V. V. Flambaum, *Phys. Rev. Lett.* **120**, 013202 (2018). [12] V. A. Dzuba, V. V. Flambaum, Y. V. Stadnik, *Phys. Rev. Lett.* **119**, 223201 (2017). [13] K. Van Tilburg, N. Leefer, L. Bougas, D. Budker, *Phys. Rev. Lett.* **115**, 011802 (2015). [14] A. Hees, J. Guena, M. Abgrall, S. Bize, P. Wolf, *Phys. Rev. Lett.* **117**, 061301 (2016). [15] P. Wcislo *et al.*, *Nature Astronomy* **1**, 0009 (2016). [16] D. Blas, D. Lopez Nacir, S. Sibiryakov, *Phys. Rev. Lett.* **118**, 261102 (2017). [17] B. M. Roberts *et al.*, *Nature Comm.* **8**, 1195 (2017).

Speaker: Dr Yevgeny Stadnik (Mainz)

Slides Stadnik_Patras_2018.pdf Stadnik_Patras_2018.ppt

11:00 → 11:30 Coffee break

11:30 → 13:10 Plenary presentation

Convener: Dr Woohyun Chung (CAPP/IBS)

11:30 Axion and hidden photon dark matter detection with multilayer optical haloscopes

A well-motivated class of dark matter candidates, including axion-like particles and dark photons, takes the form of coherent oscillations of a light bosonic field. If the dark matter couples to Standard Model states, it may be possible to detect it via absorptions in a laboratory target. Current experiments of this kind include cavity-based resonators that convert bosonic dark matter to electromagnetic fields, operating at microwave frequencies. We propose a new class of detectors at higher frequencies, from the infrared through the ultraviolet, based on the dielectric haloscope concept. In periodic photonic materials, bosonic dark matter can efficiently convert to detectable single photons. With feasible experimental techniques, these detectors can probe significant new parameter space for axion and dark photon dark matter in the 0.1 − 10 eV mass range.

Speaker: Dr Junwu Huang (Perimeter Institute of Theoretical Physics)

Slides desy.pdf

11:50 Topological Insulators as Axion Laboratories

t.b.a.

Speaker: Dr David Marsh (University of Goettingen)

Slides mev_axion_detection_marsh.pdf mev_axion_detection_marsh.pptx

12:10 Diffuse axion-like particle searches

We propose a new method to search for axion-like particles (ALPs) based on the gamma-rays produced concomitant with high-energy astrophysical neutrinos. The existence of high-energy neutrinos implies production of gamma-rays in the same sources. Photons can convert into ALPs in the sources' magnetic fields, and will travel as ALPs through extragalactic space. Back-conversion in the Milky Way's magnetic field leads to a diffuse anisotropic high-energy photon flux that existing and upcoming gamma-ray detectors, like HAWC, CTA, and LHAASO can detect. This method probes unexplored ALP parameter space, with LHAASO being realistically sensitive to couplings above 10^{−11} GeV^{−1} and masses up to 3×10^{−6} eV in ten years. Our technique also explores viable ALP dark matter parameter space.

Speaker: Dr Ranjan Laha (Johannes Gutenberg University Mainz)

Slides Patras_2018.pdf

12:30 Searching for solar KK axions with a gaseous detector

In theories with extra dimensions, the standard QCD axion has excited states with higher mass. The axion of such theories, named the Kaluza-Klein (KK) axion, would have a significantly shorter decay time for higher mass states. This would allow for axion decays on Earth, even in the absence of a strong magnetic field. It would also mean that a fraction of heavier mass axions created in the Sun would remain gravitationally trapped in the Solar System, dominating the local density of axions. NEWS-G is a dark matter direct detection collaboration that aims to detect low mass WIMPs using a gaseous target detector. The detector is a gas-filled metallic sphere with a high voltage electrode in its centre. While WIMP detection is its main purpose, it is also particularly suitable to KK axion detection. Since the rate of KK axion decays depends only on volume, not on mass, the use of a low density target is an asset: it allows to distinguish such decays from the background by identifying the separate location of the capture of the two resulting photons. In this talk, I will briefly cover the arguments in favour of the existence of (solar) KK axions. Then, I will describe the detector, and how our event discrimination works. Finally, I will present preliminary exclusion limits on KK axion coupling constant to photons, and the data and analysis leading to that limit.

Speaker: Mr Francisco Andres Vazquez de Sola (Queen's University)

Slides PATRAS_2018_presentation.pdf

12:50 Enhanced Effects of Dark Matter

Low-mass boson dark matter particles produced after Big Bang form classical field and/or topological defects. In contrast to traditional dark matter searches, effects produced by interaction of an ordinary matter with this field and defects may be first power in the underlying interaction strength rather than the second power or higher (which appears in a traditional search for the dark matter).This may give an enormous advantage since the dark matter interaction constant is extremely small. Interaction between the density of the dark matter particles and ordinary matter produces both ‘slow’ cosmological evolution and oscillating variations of the fundamental constants including the fine structure constant alpha and particle masses. Atomic Dy, Rb and Cs spectroscopy measurements and the primordial helium abundance data allowed us to improve on existing constraints on the quadratic interactions of the scalar dark matter with the photon, electron, quarks and Higgs boson by up to 15 orders of magnitude. Limits on the linear and quadratic interactions of the dark matter with W and Z bosons have been obtained for the first time [1,2]. In addition to traditional methods to search for the variation of the fundamental constants (atomic clocks, quasar spectra, Big Bang Nucleosynthesis, etc) we discuss variations in phase shifts produced in laser/maser interferometers (such as giant LIGO, Virgo, GEO600 and TAMA300, and the table-top silicon cavity and sapphire interferometers) [3,4]. Corresponding measurements which have significantly improved limits on the topological defect dark matter have been performed in [5]. Dark matter may produce changes in pulsar rotational frequencies (which may have been observed already in pulsar glitches), non-gravitational lensing of cosmic radiation and the time-delay of pulsar signals [6]. Other effects of dark matter and dark energy include apparent violation of the fundamental symmetries: oscillating or transient atomic electric dipole moments, precession of electron and nuclear spins about the direction of Earth’s motion through an axion dark matter (the axion wind effect), and axion-mediated spin-gravity couplings [7-9], violation of Lorentz symmetry and Einstein equivalence principle [10]. Recent measurements by nEDM collaboration [11] improved the limits on interaction of the low-mass axion with gluons and nucleons up to 3 orders of magnitude. Recently we investigated possibilities to detect linear effects in the axion interaction constants using interference between axion and photon atomic capture amplitudes [12] and coherent axion-photon transformations in the forward scattering on atoms [13]. Effects of scalar field produced by massive bodies on atomic transition frequencies have been experimentally investigated in [14]. Improved limits on the axions and low mass Z’- bosons have been derived from the measurements of atomic and molecular electric dipole moments [15] and parity violating effects [16]. We explore a possibility to explain the DAMA collaboration claim of dark matter detection by the dark matter scattering on electrons. We have shown that the electron relativistic effects increase the ionization differential cross section up to 3 orders of magnitude [17,18]. Recent results of ZENON collaboration [19] based on our calculations contradict to DAMA results. We investigated possible effect of finite photon mass due to magnetic interaction in plazma on galaxy rotation curve [20]. Slowly varying vector potential A of a low-mass photon field provides negative pressure P=-E/3 in the electromagnetic stress tensor (E is the magnetic field energy density), imitates gravitational pull and may provide observed distribution of the rotational velocities in the Galaxy (without dark matter!). References. [1] Can dark matter induce cosmological evolution of the fundamental constants of Nature? Y. V. Stadnik and V. V. Flambaum. Phys. Rev. Lett. 115, 201301 (2015). [2] Improved limits on interactions of low-mass spin-0 dark matter from atomic clock spectroscopy, Y. V. Stadnik, V. V. Flambaum, Phys. Rev. A 94, 022111, (2016). [3] Searching for Dark Matter and Variation of Fundamental Constants with Laser and Maser Interferometry. Y. V. Stadnik and V. V. Flambaum. Phys. Rev. Lett. 114, 161301 (2015). [4] Enhanced effects of variation of the fundamental constants in laser interferometers and application to dark matter detection, Y. V. Stadnik, V. V. Flambaum, arXiv:1511.00447 [5] P. Wcislo et al. Nature Astronomy1, 0009 (2016). [6] Searching for Topological Defect Dark Matter via Nongravitational Signatures. Y. V. Stadnik and V. V. Flambaum. Phys. Rev. Lett. 113, 151301 (2014). [7] Axion-induced effects in atoms, molecules and nuclei: Parity nonconservation, anapole moments, electric dipole moments, and spin-gravity and spin-axion momentum couplings. Y. V. Stadnik and V. V. Flambaum. Phys. Rev. D 89, 043522 (2014). [8] Limiting P-odd Interactions of Cosmic Fields with Electrons, Protons and Neutrons. B. M. Roberts, Y. V. Stadnik, V. A. Dzuba, V. V. Flambaum, N. Leefer and D. Budker. Phys. Rev. Lett. 113, 081601 (2014). [9] Parity-violating interactions of cosmic fields with atoms, molecules and nuclei: Concepts and calculations for laboratory searches and extracting limits. B. M. Roberts, Y. V. Stadnik, V. A. Dzuba, V. V. Flambaum, N. Leefer and D. Budker. Phys. Rev. D 90, 096005 (2014). [10] Enhanced violation of the Lorentz invariance and Einstein equivalence in atoms and nuclei, V.V. Flambaum. Phys. Rev. Lett. 2016. [11] C. Abel et al. (nEDM collaboration), Phys. Rev. X7, 041034 (2017). [12] Interference-assisted resonant detection of axion-like particles. H. B. Tran Tan, V. V. Flambaum, I. B. Samsonov, Y. V. Stadnik, D. Budker, arxiv: 1803.09388, [13] Coherent axion-photon transformations in the forward scattering on atoms. V.V. Flambaum, I. Samsonov, D. Budker. [14] Search for the effect of massive bodies on atomic spectra and constraints on Yukawa-type interactions of scalar particles, N. Leefer, A. Gerhardus, D. Budker, V. V. Flambaum, Y. V. Stadnik, Phys. Rev. Lett. 117, 271601 (2016). [15] Improved limits on axion-like-particle-mediated P,T-violating interactions between electrons and nucleons from electric dipole moments of atoms and molecules, Y. V. Stadnik, V. A. Dzuba, V. V. Flambaum, Phys. Rev. Lett. 120, 0132024 (2018) [16] Probing low-mass vector bosons with parity nonconservation and nuclear anapole moment measurements in atoms and molecules. V. A. Dzuba, V. V. Flambaum, Y. V. Stadnik, Phys. Rev. Lett. 119, 223201 (2017) [17] Ionization of atoms by slow heavy particles, including dark matter. B. M. Roberts, V. V. Flambaum, and G. F. Gribakin, Phys. Rev. Lett. 116, 023201 (2016). [18] Dark matter scattering on electrons: Accurate calculations of atomic excitations and implications for DAMA signal. B.M. Roberts, V.A. Dzuba, V.V. Flambaum, M. Pospelov, Y.V. Stadnik, Phys. Rev.D93, 115037 (2016). [19] E. Aprile et al (XENON collaboration) Search for Electronic Recoil Event Rate Modulation with 4 Years of XENON100 Data. Phys. Rev. Lett. 118, 101101 (2017) [20] A hypothetical effect of the Maxwell-Proca electromagnetic stresses on galaxy rotation curves. D.D. Ryutov, D. Budker, V. V. Flambaum, arxiv:1708.09514

Speaker: Prof. Victor Flambaum (University of New South Wales)

Slides FlambaumPatras2018.ppt

13:10 → 14:30 Lunch break

14:30 → 15:50 Plenary presentations

Convener: Dr maurizio giannotti (Barry Universtiy)

14:30 The Klash Proposal: Status and Perspectives

We recently proposed [arXiv:1707.06010] a search of galactic axions with mass about 0.2 $\mu$eV using a large volume resonant cavity, tens of cubic meters, cooled down to 4 K and immersed in a moderate axial magnetic field of about 0.6 T generated inside the superconducting magnet of the KLOE experiment located at the National Laboratory of Frascati of INFN. This experiment, called KLASH (KLoe magnet for Axion SearcH), has a potential sensitivity on the axion-to-photon coupling, $g_{a\gamma\gamma}$, of about $6\times10^{-17}$ $\mbox{GeV}^{-1}$, reaching the region predicted by KSVZ and DFSZ models of QCD axions. We will present the results of detailed mechanical and electromagnetic simulations of the cryostat and resonant cavity and improved studies of the Squid amplifier and of the tuning system. We will then discuss the discovery potential of axions and other light particles with this realistic setup and the strategies to extend the bandwith from 50 MHz foreseen in the original proposal to hundreds MHz.

Speaker: Dr Claudio Gatti (INFN)

Slides Patras2018GattiKlash.pdf

14:50 Search for dark matter induced neutrinos with the Super-Kamiokande detector

Indirect searches for dark matter are performed based on atmospheric neutrino data collected with the Super-Kamiokande (SK) detector in years 1996-2016. The excess of neutrinos from possible dark matter sources such as Sun, Earth and Galactic Center, compared to the expected atmospheric neutrino background is searched. Angular distributions and energy spectra as expected for signal and background are taken into account and various dark matter annihilation channels are considered. All event samples (fully-contained, partially-contained along with upward-going muons), including both electron and muon neutrinos, covering a wide range of neutrino energies (GeV to TeV) are used. The allowed number of dark matter induced neutrinos which can be contained in SK data so far is estimated. Obtained limits on dark matter induced neutrino flux are related to the limit on spin-dependent (for the Sun) and spin-independent (for the Sun and the Earth's core) WIMP-nucleon scattering cross section and compared against the results of direct detection experiments. In case of the Galactic Center analysis, the upper limit on the dark matter self-annihilation cross-section is derived.

Speaker: Ms Katarzyna Frankiewicz (National Centre for Nuclear Research)

Slides Frankiewicz_PATRAS2018.pdf

15:10 Ultra-light axions and the CMB

Ultra-light axions arise generically in string compactifications and furnish an attractive possibility for dark matter and dark energy in the universe. I'll review the cosmological implications of ultra-light axions, covering phenomenology ranging from CMB power spectra to galaxy weak-lensing observations. After summarizing current constraints, I'll discuss the exciting axionic sensitivity of future surveys and experiments like the Large Synoptic Survey Telescope and CMB-SIV. I'll close by discussing a variety of open theoretical problems, ranging from an accurate treatment of the axion sound speed to a proper treatment of nonlinear collapse and structure formation in ultra-light axion scenarios.

Speaker: Prof. Daniel Grin (Haverford College)

Slides grin_patras_2018c.pdf

15:30 Axion-plasmon polariton in stronlgy magnetized plasmas: a novel way to probe axions

Axions are hypothetical particles related to the violation of the charge-parity symmetry within the strong sector of the Standard Model, being one of the most prone candidates for dark matter. Multiple attempts to prove their existence are currently performed in different physical systems. Here, we predict that axions may couple to the electrostatic (Langmuir) modes of a strongly magnetized plasma, and show that a new quasi-particle can be defined, the {\it axion-plasmon polariton}. The excitation of axions can be inferred from the pronounced modification of the dispersion relation of the Langmuir waves, a feature that we estimate to be accessible in state-of-the-art plasma-based experiments. We discuss possible experimental setups where the axion-plasmon polariton method can probe or exclude axions and anticipate some astrophysical implications of the axion-plasmon coupling.

Speaker: Dr Hugo Terças (Instituto Superior Técnico, University of Lisbon)

Slides PATRAS_2018_TERCAS.pdf

15:50 → 16:20 Coffee break

16:20 → 17:30 Plenary short presentations

Convener: Dr Axel Lindner (DESY)

16:20 Axion effect on the minimum stellar mass that experiences central carbon burning

We study the effect of axions in the evolution of stars that are close to the minimum stellar mass that experiences central carbon burning, called Mup. This mass limit is a fundamental property in astrophysics as it defines which stars end their evolution as carbon-oxygen white dwarfs (CO WDs) and which ones as oxygen-neon white dwarfs, electron-capture supernovae and normal core collapse supernovae (CCSNe). We consider DFSZ axions produced by Primakoff, Compton and Bremsstrahlung processes, adopting for the coupling constants to photons and electrons a set of values from zero (no axions) to maximum values that take into account updated constraints derived from Globular Cluster properties, as the luminosity of the RGB tip and the R parameter. Our results show that axions may increase Mup to values that are in tension with the observationaly derived minimum mass of CCSNe progenitors and with the maximum stellar mass that produces a CO WD.

Speaker: Prof. Inma Dominguez (Universidad de Granada)

Poster Axions_InmaDominguez_poster.pdf

Slides Axions_InmaDominguez_5minutes.pdf

16:25 The Higgs boson can delay reheating after inflation

We show that fluctuations of the Standard Model Higgs boson field yield large particle masses dur- ing inflation and reheating, and in turns to a temporary blockage of the reheating process and a lower reheat temperature after inflation. We study the effects on the multiple stages of reheating: resonant particle production (preheating) as well as perturbative decays from coherent oscillations of the inflaton field. The reheat temperature can decrease by up to an order of magnitude due to this effect. In the case of gauge-reheating, Higgs-generated masses of the gauge fields can suppress preheating even for large inflaton-gauge couplings. In extreme cases, preheating can be shut down completely and must be substituted by perturbative decay as the dominant reheating channel. Finally, we discuss the distribution of reheat temperatures in different Hubble patches, arising from the stochastic nature of the Higgs VEV during inflation and its implications for the generation of both adiabatic and isocurvature fluctuations.

Speaker: Dr Luca Visinelli (Stockholm University)

Slides Visinelli_Patras2018.pdf

16:30 Dilute and dense axion stars

Axion stars are hypothetical objects formed of axions, obtained as localized and coherently oscillation solution to the classical equation of motion. I will discuss the family of axion star solutions for QCD axions. Depending on the value of the field amplitude at the core $\theta_0$, the equilibrium of the system arises from the balance of kinetic pressure and either self-gravity or axion self-interactions. I will show how the usual non-relativistic approximation breaks down for field values approaching $\mathcal{O}(\theta_0) = 1$. This *dense* regime can be described using a multi-harmonic expansion to solve the relativistic equation; we find that in this regime the life-time of the axion star is much shorter than any timescale relevant for cosmology.

Speaker: Sebastian Baum (OKC & Stockholm University)

Poster 18Patras_Poster.pdf

Slides SB_Patras.pdf

16:35 Exchange-Correlation Effects in Axion Structure Formation

The search for QCD axion dark matter is well underway. Many of these searches require detailed knowledge of the axion's cosmological distribution. However, our understanding of axion structure formation is far from complete, due largely to the candidate's highly-degenerate state. This talk presents a new model of axion structure formation that includes the quantum nature of condensed Bose fluids. Theory and preliminary simulations show notable deviations from mean field approaches.

Speaker: Dr Erik Lentz (University of Goettingen)

Slides EWL_Patras_2018_Talk.pdf

16:40 Changes in effective points of reflection in the ALPS II regeneration cavity

**ALPS II** The Any Light Particle Search (ALPS) II is a Light-Shining-Through-a-Wall type experiment which will consist of two optical resonators to enhance the rates of 1064 nm photons oscillating into Axion-like-particles (ALPs) and vice-versa. [1] **Dichroic locking scheme** Both cavities have to be resonant for the same spatial mode and their lengths need to be controlled so that photons of the same frequency are resonant in both cavities. Frequency locking of the regeneration cavity will be done with a second laser of different wavelength to easily seperate this control beam from regenerated photon signals. For this purpose, ALPS II will use the frequency double of the ALPs producing beam, a 532 nm control beam. [1] **Effective points of reflection** To make two different wavelengths resonant at the same time in the regeneration cavity, the involved mirror coatings have to be specified for both wavelengths accordingly. This is typically done by adding two different coating stacks on top of each other, thus, the two different wavelengths have different penetration depths into the coatings and see different optical lengths of the cavity. [2] The differential frequency shift between the two beams can be anywhere between zero and one full free spectral range of the cavity. In ALPS II, this shift, once it is known, can be easily compensated by the control electronics of the frequency stabilization. [3] **Change of effective points of reflection over time** A challenge for ALPS II is the possibility of a temperature-induced change of the difference in the effective points of reflection over time. The control electronics can only compensate for constant frequency differences between the two beams. If there is a drift in the effective points of reflection on the mirror coatings it will translate into a frequency mismatch between the control beam and the signal beam in the regeneration cavity, spoiling the enhancement factor of photon regeneration and thus, limiting the overall sensitivity of ALPS II. **Mirror-coating test bed at AEI in Hannover** To minimize the change in effective points of reflection specific coatings were designed, fabricated and need to be tested. For this purpose, a test experiment is set-up at AEI in Hannover to monitor the difference frequencies in a high finesse Fabry-Pérot cavity over different temperatures. The objective is to find mirror coatings with small enough temperature dependence of the effective point of reflection not to limit the ALPS II sensitivity. **References** [1] R. Bähre et al., Any light particle search II – Technical Design Report, IOP Publishing, 2013 [2] R. Bähre, Design and setup of an optical experiment for searching for weakly interacting sub-eV particles (WISPs) that couple to an electro-and/or magnetic field, Dissertation, Leibniz Universität Hannover, 2016 [3] A. D. Spector, J. H. Pöldet al., Characterization of optical systems for the ALPS II experiment, arXiv:1609.08985v2, Nov. 2016

Speaker: Mr Dennis Schmelzer (AEI Hannover)

Poster Changes in effective points of reflection in the ALPS II regeneration cavity

Slides Changes in effective points of reflection in the ALPS II regeneration cavity Backup slides in 4:3 scale. Do not use if 16:9 is working!

16:45 Photon-Axion Conversion and Magnetic Field Configuration

Cosmological magnetic field can induce conversion between photon and axion. The origin of cosmological magnetic field is still outstanding problem, and its actual configuration is not well known. However, most previous studies on conversion have been carried out in one simple magnetic configuration. In this talk, I will discuss photon-axion conversion process in another magnetic configuration, assuming that its origin is primordial. In particular, we investigate the evolution of photon polarization during conversion process and show similarities and differences between different magnetic configurations.

Speaker: Ms Emi Masaki (Kobe University)

Poster PATRAS2018.pdf

Slides PATRAS_5min.pdf

16:50 Cosmological Simulations with Ultralight Axion Dark Matter

Dark matter consisting of ultralight axions gives rise to a unique density structure on galactic scales. Insight to these processes can be gained by numerical simulations. I will give an overview of simulation results and their implications for observational probes.

Speaker: Mr Jan Veltmaat (Göttingen)

Slides presentation.odp presentation.pdf

16:55 Constraints on Fuzzy Dark Matter Models from Planck 2015 Data

An ultralight scalar field is a viable candidate for dark matter (fuzzy dark matter), which could resolve the so-called small-scale problems accompanying the standard cold dark matter model. The fuzzy dark matter has quantum pressure arising from the gradient energy of the field, and behaves differently from the cold dark matter on small scales. The quantum pressure affects various observations, e.g., cosmic microwave background (CMB) and large scale structure of the universe. In this talk, I will discuss constraints on the fuzzy dark matter models from CMB observation using the Planck 2015 data.

Speaker: Mr Arata Aoki (Kobe University)

Poster aoki_poster.pdf

Slides aoki_slides.pdf

17:00 Millicharged fermion vacuum polarization and superluminal photon propagation.

In this talk I discuss the possibility of vacuum polarization due to millicharged fermions in a gravitational field and the possibility of superluminal photon propagation in an expanding universe. Vacuum polarization in a graviational field is known to generate photon superluminal propagation in many situations such as in the metric of a black hole, in an expanding universe etc. Based on the recent observations made by LIGO/VIRGO, I discuss the implications that millicharged fermion vacuum polarization has on the velocity of photons from astrophysical sources such as that of GW170817. In addition, I discuss some constraints on the millicharged fermion parameter space based on the electromagnetic counterpart of the GW170817 source detected by the FERMI-GMB collaboration.

Speaker: Dr Damian Ejlli (Novosibirsk State University)

17:05 New Limits on Axion-Photon Coupling Constant for Solar Axions.

A search for resonant excitation of the first nuclear level of $^{83}\rm{Kr}$ (9.4 keV) by axions formed in the Sun due to the Primakov effect have been carried out. To register the $\gamma$ and X-ray quanta, conversion and Auger electrons arising from the discharge of the nuclear level, we used a gas proportional counter located in a low-background setup in the Baksan underground laboratory of INR RAS. As a result, a new constraint on the coupling constant of the axion with the photon and the mass of the axion $|g_{A\gamma}\times m_A|\leq 6.3 \times 10^{-17}$, which in the KSVZ hadronic axion model corresponds to a new limit on the mass of the axion $m_A \leq 12.7$ eV for 95 \% c.l.

Speaker: Mr Evgeniy Unzhakov (Petersburg Nuclear Physics Institute)

Slides Unzhakov_Patras_2018.pdf

17:10 High energy resolution metallic magnetic calorimeters for the IAXO experiment

The International Axion Observatory (IAXO) will be a fourth generation axion helioscope, for the search of axions generated at the core of the Sun. The detection principle used for the IAXO experiment is based on the Primakoff effect. Solar axions reaching the Earth could be converted into photons while passing through a volume under high and static magnetic field. The expected photon spectrum has a continuum shape which is peaked at about 4 keV. IAXO is therefore characterized by three main components: a long and strong magnet pointing towards the Sun, x-ray optics and high resolution and low background x-ray detectors. Low temperature metallic magnetic calorimeters (MMCs) are one of the detector technologies selected for IAXO. MMCs are energy dispersive detectors operated at temperatures below 0.1 K. In MMCs, the magnetization of the sensor is used to monitor the temperature change of the detector upon the interaction of a particle. This temperature change is proportional to the absorbed energy. Low-noise high-bandwidth dc-SQUIDs read out small changes in magnetization. The resolving power approaching 5000, the intrinsic response time well below 1 µs and the excellent linearity make MMCs very attractive for IAXO. In particular, the very good energy resolution of MMCs will increase the sensitivity of the experiment on the axion-electron coupling. We present the development of a $64\times64$-pixel array covering a relatively large surface, $45\times45$ mm$^2$ and characterized by a moderate energy resolution of about 200 eV which is suitable for the search of solar axion signals. A second design, a 64-pixel array covering a surface of about 4 mm$^2$, optimized for high resolution x-ray spectroscopy and able to reach energy resolution smaller than 2 eV will be discussed for investigating axion-electron coupling. Both proposed arrays will be read out by 32 double stage SQUID channels, allowing for the development of a common detector platform for the operation of the detectors in a movable cryostat.

Speaker: Dr Loredana Gastaldo (Kirchhoff-Institut für Physik, Universität Heidelberg)

Poster Poster_template_v2.pdf

Slides PATRAS_Gastaldo_slides.pdf

17:15 SMASH-ing Vacuum Metastability

Five fundamental problems - neutrino oscillations, baryogenesis, dark matter, inflation, strong CP problem - are solved at one stroke in a model, dubbed as "SM-A-S-H" (Standard Model-Axion-Seesaw-Higgs portal inflation) by Andreas Ringwald et. al. The Standard Model (SM) particle content is extended by three right-handed SM-singlet neutrinos $N_i$, a vector-like color triplet quark $Q$, a complex SM-singlet scalar field $\sigma$ that stabilises the Higgs potential, all of them being charged under a global lepton number (hyper-charge) and Peccei-Quinn (PQ) U(1) symmetry, the vacuum expectation value $v_\sigma \sim 10^{11}$ GeV breaks the lepton number and the Peccei-Quinn symmetry simultaneously. We found that numerically SMASH model not only solves five fundamental problems but also the sixth problem "Vacuum Metastability" through the extended scalar sector.

Speaker: Dr Chitta Ranjan Das (Bogoliubov Laboratory of Theoretical Physics (BLTP), Joint Institute for Nuclear Research (JINR), Dubna, Russian Federation)

Slides SMASH-ing Vacuum Metastability

17:20 Extragalactic photon--axion-like particle oscillations up to 1000 TeV

Axion-like particles (ALPs) are very light, neutral, pseudo-scalar bosons which are supposed to interact with two photons. They can give rise to very interesting astrophysical effects taking place in the very-high energy band and above ($10 \, {\rm GeV}-1000 \, {\rm TeV}$) when an external magnetic field is present. So far, the extragalactic magnetic field $B_{\rm ext}$ has been generally modeled as a domain-like network with ‘sharp edges’: all domains have the same size $L_{\rm dom}$ and $B_{\rm ext}$ has the same strength, but the direction of $B_{\rm ext}$ changes randomly and abruptly from one domain to the next. While this model has repeatedly been used so far, it is a mathematical idealization wherein the components of $B_{\rm ext}$ are discontinuous across the edges. Still, it gives correct results under the unstated assumption that the photon-ALP oscillation length $l_{\rm osc}$ is much larger than $L_{\rm dom}$. However, for the new generation of $\gamma$-ray observatories like CTA, HAWC, GAMMA-400, LHAASO and TAIGA-HiSCORE things are different: photon dispersion on the CMB implies $l_{\rm osc} < L_{\rm dom}$, which occurs just above the TeV scale. In such a situation the above model breaks down and must be replaced by one in which $B_{\rm ext}$ is continuous across the edges. We describe such a new model and apply it to a sample of mock blazars at different $z$ and at energy $E$ up to $1000 \, \rm TeV$. We analyze the propagation of the photon-ALP beam generated as pure photons at the jet base of a BL Lac, we study the photon-ALP oscillations during its path up to us while crossing the BL Lac magnetic field, the extragalactic magnetic field which we describe by means of our new model and the Milky Way magnetic field.

Speaker: Dr Giorgio Galanti (INAF, Osservatorio Astronomico di Brera)

Poster Galanti-ALPs-poster-hamb.pdf

Slides Galanti-ALPs-slides-hamb.pdf

17:30 → 18:30 Drinks at the posters

17:30 Contributions: see previous session

Tuesday 19 June

09:00 → 09:35 Gravitational waves and modified gravity

I will discuss the implication of the recent measurement by LIGO of the speed of gravitational waves on models of modified gravity, mainly for mechanisms for acceleration but also for alternatives to dark matter. I will discuss the remaining parameter space and the sort of physics we might still expect to see in the upcoming generation of cosmological surveys focused on measuring the properties of the dark sector.

Speaker: Dr Ignacy Sawicki (CEICO, Institute of Physics, Czech Academy of Sciences)

Slides Sawicki_DESY.pptx

09:35 → 10:55 Plenary presentations

Convener: Prof. Yannis Semertzidis (CAPP/IBS and KAIST)

09:35 Results from NA62

The decay K+→π+νν, with a very precisely predicted branching ratio of less than 10^{-10}, is one of the best candidates to reveal indirect effects of new physics at the highest mass scales. The NA62 experiment at CERN SPS is designed to measure the branching ratio of the K+→π+νν with a decay-in-flight technique, novel for this channel. NA62 took data in 2016, 2017 and another year run is scheduled in 2018. Statistics collected in 2016 allows NA62 to reach the Standard Model sensitivity for K+→π+νν, entering the domain of 10-10 single event sensitivity and showing the proof of principle of the experiment. The analysis data is reviewed and the preliminary result from the 2016 data set presented. In addition, owing to the high beam-energy and a hermetic detector coverage, NA62 also has the opportunity to directly search for a plaethora of long-lived beyond-the Standard Model particles, such as Axion-like Particles and Dark Photons. W will review the status of this searches and give prospects for future data taking at NA62.

Speaker: Döbrich Babette (CERN)

Slides bd_PATRAS_2018.pdf

09:55 Directional axion detection

I will discuss how to extend existing axion haloscope designs into specialised modes that are sensitive to the directionality of the axion signal. This is particularly advantageous if one wants to probe the structure our local velocity distribution of dark matter. A directional experiment can grant us a three-dimensional view of this distribution and allow the discovery of the network of tidal streams and phase space substructure likely to be present in our halo.

Speaker: Dr Ciaran O'Hare (Universidad de Zaragoza)

Slides OHare-fv.pdf

10:15 Axion emissitivity and detectability from supernove

I present a re-evaluation of the emissivity of axions from core-collapse supernvae based on state-of-the art simulations. I also discuss the perspective of detection of an axion signal in large underground neutrino detectors.

Speaker: Dr Alessandro Mirizzi (University of Bari)

Slides SN_patras_mirizzi.pdf

10:35 Axions and the white dwarf luminosity functions of the galactic disks and halo

The evolution of white dwarfs is a simple gravothermal process of cooling. Since the shape of their luminosity function is sensitive to the characteristic cooling time, it is possible to use its slope to test the existence of additional unexpected sources or sinks of energy. The aim of this paper is to study if the changes in the slope of the white dwarf luminosity function around bolometric magnitudes ranging from 8 to 10 previously attributed to axion emission are, effectively, caused by an intrinsic property or they are just an artifact introduced by the star formation rate. In this talk we compute theoretical luminosity functions of the thin and thick disks, and of the stellar halo and we compare them with the presently observed luminosity functions. Since these stellar populations have different star formation histories, the change of slope should be present at the same place in all of them if it is due to an intrinsic cooling mechanism like axions. Our results suggest that effectively, this signature is present in all the luminosity functions and, therefore, has an intrinsic character. This additional cooling is compatible with axion emission and gives support to the possible existence of DFSZ axions with masses in the range of 4 to 10~meV. If this were the case, these axions could be detected by the future solar axioscope IAXO.

Speaker: Prof. Jordi Isern (ICE,CSIC/IEEC)

Slides Isern_patras18.pdf

10:55 → 11:30 Coffee break

11:30 → 13:10 Plenary presentations

Convener: Dr Loredana Gastaldo (Kirchhoff-Institut für Physik, Universität Heidelberg)

11:30 Illuminating axion stars

t.b.a.

Speaker: Dr David Marsh (University of Cambridge)

Slides Illuminating_axion_stars.pptx

11:50 BRASS: Broadband Radiometric Axion SearcheS

We present here a modification of the spherical reflector approach proposed for broadband searches for axion dark matter. The new concept foresees the use of a permanently magnetized surface ({\em magnetized converter}) employed for axion/ALP$-$photon conversion. The magnetized converter comprises a two-dimensional Halbach array providing a sufficiently homogeneous magnetic field with a $B_{||}\sim$$1\,$T component parallel to the surface and concentrated within about 1$\,$cm height above it. This enables effective conversion of dark matter axions and ALPs with masses above $\approx $$80\,\mu$eV (20 GHz). Based on this modification, a conceptual design for broadband radiometric axion searches (BRASS) has been developed, aiming at providing an experimental facility for WISP dark matter searches in the 20$\,$GHz$-$1$\,$THz (0.08$-$4 meV) range. Details of the experiment design, expected sensitivities to WISP dark matter, and present plans for constructing the first prototype setup will be discussed.

Speaker: Dr Andrei Lobanov (MPIfR Bonn / Universität Hamburg)

Slides Lobanov

12:10 Axion monodromy dark matter and fluctuations

Axion-like particles (ALP), produced via the misalignment mechanism are interesting candidates for cold dark matter, both from the theoretical as well as the experimental perspective. The standard potential of ALPs is periodic and bounded from above. Recently interest has grown towards situations where the periodicity is broken, giving rise to a potential with many non-degenerate minima. For example in string theory such scenario can be realized using the phenomenon of monodromy. Importantly, this extends the range of viable ALP dark matter models towards larger experimentally more accessible couplings. At the same time the structure of the potential with many minima results in a non-trivial time evolution and a growth of fluctuations. In this talk we consider the case of breaking with a quadratic monomial, which corresponds to the massive Sine-Gordon model. We perform an analysis of the full nonlinear dynamics and discuss how the instabilities of the coherent oscillations trigger the growth of quantum fluctuations, which can lead to significant deviations from an expected matter-like equation of state. We discuss the effects of the complex structure of the potential, such as the averaging out of the interactions and the transitions between local minima.

Speaker: Mr Aleksandr Chatrchyan (Heidelberg University, Institute for theoretical physics)

Slides monodromy-patras.pdf

12:30 ALPS II: Overview and Status Report

ALPS II is a light shining through a wall style experiment that will use optical cavities to resonantly enhance the coupling between photons and axion-like particles in the mass range below 1 meV. In the last year there has been significant experimental progress in the development of the optical system and the single photon detection schemes, as well as progress related to the preparation of the magnets and the on site infrastructure. An overview of the experiment and its current status will be discussed.

Speaker: Dr Aaron Spector (DESY)

Slides PATRAS_2018.pdf

12:50 Search for gamma-ray spectral modulations in Galactic pulsars as a result of photon-ALPs mixing.

Well-motivated extensions of the standard model predict ultra-light and fundamental pseudo-scalar particles (e.g., axions or axion-like particles: ALPs). Similarly to the Primakoff-effect for axions, ALPs can mix with photons and consequently be searched for in laboratory experiments and with astrophysical observations. Here, we search for energy-dependent modulations of high-energy gamma-ray spectra which are the evidential signatures of photon-ALPs mixing. To verify this, we analyze the data recorded with the Fermi-LAT from Galactic pulsars selected to have a line of sight crossing spiral arms at a large pitch angle. For the six selected Galactic pulsars, the energy spectrum is well described by a smooth model spectrum (a power-law with a sub-exponential cut-off) while a common fit of the ALPs parameters improves the goodness of fit in comparison to a smooth model spectrum with a significance of 4.6 σ. We determine the most-likely values for ALPs mass and photon-ALPs coupling constant which are by a factor of ≈ 3 larger than the current best limit on solar ALPs generation obtained with the CAST helioscope, although known modifications of the photon-ALP mixing in the high density solar environment could provide a plausible explanation for the apparent tension between the helioscope bound and the current indication for photon-ALPs mixing.

Speaker: Ms Jhilik Majumdar (PhD student in UniHH)

Slides presentation_PATRAS.pdf

13:10 → 14:30 Lunch break

14:30 → 16:30 Plenary presentations

Convener: Andreas Ringwald (DESY)

14:30 QCD Axion from Flavour Symmetry

We show how an accidental U(1) Peccei-Quinn symmetry can arise in a realistic Pati-Salam unified theory of flavour. A QCD axion arises from a linear combination of A4 triplet favons, which are responsible for fermion flavour structures and thus specific favour-violating couplings of the axion are predicted. We discuss the prospect of probing such a flavourful axion in future experiments.

Speaker: Prof. Eung Jin Chun (Korea Institute for Advanced Study)

Slides 180619-PATRAS-Chun.pdf

14:50 CAPP’s pilot axion experiment with a target mass range around 10 µeV

CAPP’s flagship axion experiment, CULTASK, employs dilution refrigerators to lower the physical temperature of resonant cavities to less than 40 mK - the coldest ever for axion search. We prepared a complete experimental setup (CAPP-PACE) equipped with an 8 T superconducting magnet with 12 cm inner bore in order to search for axions with mass around 10 µeV. The frequency tuning system installed in a split-design resonant cavity with a high Q-factor utilizes piezoelectric actuators with interchangeable sapphire and copper rods and performs flawlessly in searching a wide range of axion mass. The feeble signal (~10^-24 W) from the cavity is amplified and transmitted through the RF receiver chain, specially designed to minimize the noise temperature of the system employing an 1 K HEMT or a quantum-limited SQUID (Superconducting Quantum Interference Device) amplifier, which eventually raise the sensitivity and speed up the axion search. I will present the results from the CAPP’s first physics data in the axion mass range from 9.83 to 11.38 µeV and discuss our future plans.

Speaker: Dr Woohyun Chung (CAPP/IBS)

Slides Woohyun_Chung_PATRAS_2018_final.pdf

15:10 MADMAX: A new road to axion dark matter detection

The Axion is the hypothetical low-mass boson predicted by the Peccei-Quinn mechanism solving the strong CP problem. It is naturally also a cold dark matter candidate, thus it could simultaneously solve two major problems of nature. Up to recently there was no existing experimental effort aiming to detect QCD axions in the mass range around 100 ueV, preferred by models in which the Peccei-Quinn symmetry was broken after inflation. The MADMAX project is designed to be sensitive for axions with masses 40ueV – 400 ueV. The experimental design is based on the idea of enhanced axion photon conversion in a system with several layers with alternating dielectric constants inside a ~10T dipole magnet. The experimental idea and the proposed design of the MADMAX experiment will be discussed. Some results from proof of principle measurements and magnet design studies will be shown. The status of R&D towards realization of the MADMAX experiment will be discussed and the prospects for reaching sensitivity enough to cover the parameter space predicted for QCD dark matter axions with mass in the range 40-400 µeV will be presented.

Speaker: Dr Bela Majorovits (MPI für Physik)

Slides presentation_patras_2018_MADMAX.pptx

15:30 Rare Low-Energy Event Searches with the MAJORANA DEMONSTRATOR

The MAJORANA DEMONSTRATOR is currently searching for neutrinoless double-beta decay in $^{76}$Ge and will demonstrate the feasibility to deploy a tonne-scale experiment in a phased and modular fashion. It consists of two modular arrays of natural and $^{76}$Ge-enriched germanium detectors totaling 44.1 kg, of which 29.7 kg is enriched, located at the 4850' level of the Sanford Underground Research Facility in Lead, South Dakota, USA. The low-backgrounds and low thresholds (< 1 keV) achieved by the DEMONSTRATOR allow for additional rare-event searches at low-energies, e.g. searches for low-mass WIMPs, bosonic dark matter, and solar axions. In this work, we will present results and ongoing efforts related to these rare-event searches and discuss the future reach of MAJORANA.

Speaker: Gulden Othman (University of North Carolina at Chapel Hill)

Slides GOthman_patras_final.pdf

15:50 Axion predictions in GUT

Non-supersymmetric Grand Unified $SO(10)\times U(1)_{\rm PQ}$ models have all the ingredients to solve several fundamental problems of particle physics and cosmology -- neutrino masses and mixing, baryogenesis, the non-observation of strong CP violation, dark matter, inflation -- in one stroke. The axion - the pseudo Nambu-Goldstone boson arising from the spontaneous breaking of the $U(1)_{\rm PQ}$ Peccei-Quinn symmetry - is the prime dark matter candidate in this setup. In this talk I will present how the axion mass can be determined in terms of the relevant gauge symmetry breaking scales in various $SO(10)\times U(1)_{\rm PQ}$ models and which constraints can be placed on these models from the requirement of gauge coupling unification. Finally I will present the steps we have taken in order towards an anlysis of the stability of the electroweak vacuum in our model.

Speaker: Anne Ernst (Desy)

Slides Patras_ERNST.pdf

16:10 The Stochastic Axion Scenario

For the minimal QCD axion model it is generally believed that overproduction of dark matter constrains the axion mass to be above a certain threshold, or at least that the initial misalignment angle must be tuned if the mass is below that threshold. We demonstrate that this is incorrect. During inflation, if the Hubble scale is low, the axion tends toward an equilibrium. This means the minimal QCD axion can naturally give the observed dark matter abundance in the entire lower part of the mass range, down to masses $\sim 10^{-11}$ eV (or $f_a$ up to the Planck scale). The axion abundance is generated by quantum fluctuations of the field during inflation. This mechanism generates cold dark matter with negligible isocurvature perturbations. In addition to the QCD axion, this mechanism can also generate a cosmological abundance of axion-like-particles and other light fields.

Speaker: Adam Scherlis (Stanford)

Slides Use if other file breaks Use this file!

16:30 → 16:45 Coffee break

16:45 → 18:10 WIMP-WISP slam

Conveners: Mr Johannes Kaub, Mrs Reinhard Teresa (MPSD)

poster Science_Slam_WIMPs,_WISPs_&.jpg

16:45 Introduction

16:50 Looking for the brightness of dark matter

We can state one thing with confidence: there's more *stuff* in our galaxy than we can see. If the galaxy were only made up of what we see, its gravity would not be strong enough to keep the outer stars from flying away as the galaxy rotates. Therefore, there is plenty of matter that is in our galaxy that we cannot see -- we call it dark matter. To find dark matter, we must create devices that are extremely sensitive to this matter that interacts so weakly with our world. In HAYSTAC, we use strong magnetic fields to convert a type of dark matter called axions into light. But just how a guitar without a body will not be loud, a photon without a resonator will not produce a strong signal. Our work requires us to create devices that resonate loudly to create a bright photon but also amplifiers that pick up weak signals, so we can know that we can see the axion signal if it is there. If we are able to observe this particle, we might be able to state that we went from understanding 5% of our universe to 30% percent!

Speaker: Nicholas Rapidis (UC Berkeley)

Slides ScienceSlam_Rapidis_Patras.pptx

17:00 Audience voting

17:02 Vacuum Magnetic Birefringence in high static magnetic fields

Overview of possible techniques to measure Vacuum Magnetic Birefringence in high static magnetic fields as LHC or Hera magnets. Heterodyne ellipsometry techniques in absence of magnetic field rotation or modulation will be presented.

Speaker: Stepan Kunc (Technical University of Liberec)

Slides PATRAS_2018_science_slam__VMB.pdf

17:12 Audience voting

17:14 On Safari in the Milky Way

We often talk about how a large chunk of our Universe is ‘missing’ in the form of the mysterious dark matter. Indeed it is true that we know very little about the identity of the elusive dark matter particle. But these days thanks to simulations we know a surprising amount about how these particles behave collectively inside galaxies and the strange shadowy creatures they like to form. By trying to catch some of these objects in the laboratory we can not only learn about the fundamental nature of dark matter but also unveil the blueprints for the Milky Way to understand how our own galaxy was built.

Speaker: Dr Ciaran O'Hare (University of Zaragoza)

Slides Slam.key

17:24 Audience voting

17:26 Here Be Dragons

The Dark Universe promises uncharted territories with wonders only limited by our imagination.

Speaker: Rafael Lang (Purdue University)

Slides rafael_here_be_dragons.pptx

17:36 Audience voting

17:38 Fractional photons

While we interact with them every day, there’s still a lot we don’t know about photons. Most light sources we deal with emit an enormous number of photons per second. But what if we were able to reduce this down to 1 photon per week? Then what if we start cutting it up into fragments? We take a look at the techniques used to not only produce fractions of photons, but also detect them in the laboratory.

Speaker: Mr Zachary Bush (Graduate Student - UF)

Slides Fractional_Photons_V4.pptx

17:48 Audience voting

18:00 Award ceremony

Wednesday 20 June

09:00 → 09:35 Small scales, big differences: nonlinear structures beyond cold dark matter

The cold dark matter (CDM) paradigm of gravitational structure formation faces its strongest challenges on small, nonlinear scales where deviations from interactions, initial conditions, or bosonic effects can become pronounced. At the same time, the growing importance of baryons makes a clear identification of beyond-CDM phenomena difficult. I will present a short overview of the existing hints for possible bCDM physics and upcoming opportunities for probing the small-scale structure of dark matter.

Speaker: Prof. Jens Niemeyer (University of Goettingen)

Slides Niemeyer_Patras_18.pdf

09:35 → 10:55 Plenary presentations

Convener: Prof. Marc Schumann (Univertity of Freiburg)

09:35 ABRACADABRA: A New Approach to the Search for Axion Dark Matter

The evidence for the existence of Dark Matter is well supported by many cosmological observations. Separately, long standing problems within the Standard Model point to new weakly interacting particles to help explain away unnatural fine-tunings. The axion was originally proposed to explain the Strong-CP problem, but was subsequently shown to be a strong candidate for explaining the Dark Matter abundance of the Universe. ABRACADABRA is a proposed experiment to search for ultralight axion Dark Matter, with a focus on the mass range $10^{-14} < m_a < 10^{-6}$ eV. We search for these axions and other axion like particles (ALPs) through a modification to Maxwell's equations, which cause strong magnetic fields to source weak oscillating electrical currents parallel to the field. In this talk, I will describe the working principle behind the ABRACADABRA experiment as well as the prototype that we are running at MIT called ABRACADABRA-10 cm.

Speaker: Prof. Lindley Winslow (MIT)

Slides Conference_PATRAS2018.key Conference_PATRAS2018.pdf

09:55 Broadband Electric-field Axion Sensing Technique (BEAST)

The mass of axion dark matter is only weakly bounded by cosmological observations, necessitating a variety of detection techniques and experiments at many different mass ranges. Axions are calculated to convert to photons via the inverse Primakoff effect and cryogenic resonant cavities are often proposed as a tool for detecting these photons. However, such structures are inherently narrowband and the range of possible axion dark matter masses spans several orders of magnitude. On the other hand broadband low-mass particle haloscopes have been proposed using inductive magnetometer sensors and a solenoid magnet of gapped toroidal geometry. In this work we propose an alternative approach, which uses a capacitive sensor in a conventional solenoidal magnet with the magnetic field aligned in the laboratory z-axis, as implemented in standard haloscope experiments. In the presence of a large DC magnetic field, the inverse Primakoff effect causes a time varying electric field (or equivalent displacement current) in the z-direction to oscillate at the axion Compton frequency. We propose non-resonant techniques to detect this electric field by implementing capacitive electric field sensors coupled to a low noise amplifier. We present the theoretical foundation for this proposal, and the first experimental results. Preliminary results constrain $g_{a\gamma\gamma} >\sim2.35\times10^{-12}$ $\text{GeV}^{-1}$ in the mass range of $2.08\times10^{-11}$ to $2.2\times10^{-11}$ eV, and demonstrate potential sensitivity to axion like dark matter with masses in the range of $10^{-12}$ to $10^{-8}$ eV.

Speaker: Prof. Michael Tobar (The University of Western Australia)

Slides Patras2018.pdf Patras2018.pptx

10:15 Status and plans of the International Axion Observatory

Axions are a natural consequence of the Peccei-Quinn mechanism, the most compelling solution to the strong-CP problem. Similar axion-like particles (ALPs) also appear in a number of possible extensions of the Standard Model, notably in string theories. Both axions and ALPs are very well motivated candidates for the Dark Matter, they appear in other cosmological scenarios involving inflation, dark radiation or even dark energy, and could also solve some long-standing anomalous astrophysical observations. If they exist, they would be copiously produced at the sun’s interior. A relevant effort during the last decade and a half has been the CAST experiment at CERN, the most sensitive axion helioscope to-date. The International Axion Observatory (IAXO) will be a fourth generation axion helioscope, born as a large-scale ambitious follow-up of CAST. As its primary physics goal, IAXO will look for solar axions or ALPs with a signal to background ratio of about 5 orders of magnitude higher than CAST. For this, IAXO envisions a large multibore superconducting magnet designed to optimize the axion helioscope figure of merit, extensive use of x-ray focusing optics and low background x-ray detectors. IAXO will venture deep into unexplored axion parameter space, thus having discovery potential. The first step of the project, called BabyIAXO, features a scaled-down system (but of dimensions representative of the full infrastructure), with a single-bore magnet and one full scale detection line. BabyIAXO will already enjoy competitive sensitivity (of about 2 orders of magnitude in signal-to-noise-ratio better than CAST) and will deliver relevant physics outcome. BabyIAXO and IAXO have also potential to host additional detection setups. Most interestingly, the large magnetic volume available could be used to host haloscope-like setups to detect relic axion or ALPs potentially composing the galactic halo of Dark Matter. IAXO has the potential to serve as a multi-purpose facility for generic axion and ALP research in the next decade.

Speaker: Dr Igor Irastorza (Universidad de Zaragoza)

Slides IAXO_Irastorza_PatrasDESY_.pptx

10:35 Searching for the neutrinoless double beta decay with GERDA

Neutrinoless double beta (0$\nu\beta\beta$) decay is a lepton-number violating process which is predicted by many extensions of the Standard Model. It could be the key to understand the nature of the neutrino. If observed, it would prove its Majorana nature and the half-life of the decay would be a direct measure of the yet unknown absolute scale of the neutrino-mass, assuming the massive neutrino exchange as the dominant process. The GERmanium Detector Array (GERDA) experiment at the INFN, Gran Sasso Laboratory, Italy, is searching for the 0$\nu\beta\beta$ decay of the isotope $^{76}$Ge. High-purity germanium crystals enriched in $^{76}$Ge are the source and the detector simultaneously. The key design feature of GERDA is that detectors are deployed directly into an ultrapure cryogenic liquid (liquid argon), acting both as cooling medium and radiation shield against the external radiation. After a major detector upgrade a second Phase (Phase II) of the experiment started in December 2015. Newly developed, custom-made BEGe-type germanium detectors made out of enriched material were deployed in the setup, allowing for a superior background rejection by pulse shape discrimination. The background suppression was further improved thanks to an active veto which detects the liquid argon scintillation light. This presentation will summarize the basic concept of the GERDA design, the recent physics results from Phase II, the status and future perspectives of the 0$\nu\beta\beta$ decay search using $^{76}$Ge.

Speaker: Prof. Riccardo Brugnera (Padova University and INFN Padova)

Slides brugnera_gerda_patras2018_v2.pdf

10:55 → 11:05 Workshop photo

11:05 → 11:25 Coffee break

11:25 → 12:30 Plenary short presentations

Convener: Babette Doebrich (DESY)

11:25 A global study of the extended scalar singlet model

We perform a global study of the extended scalar singlet model with a fermionic dark matter (DM) candidate. Using the most up-to-date results from the Planck measured DM relic density, direct detection limits from the PandaX-II experiment, electroweak baryogenesis (EWBG), electroweak precision observables (EWPO) and Higgs searches at colliders, we constrain the 7-dimensional model parameter space. We also find regions in the model parameter space where a successful EWBG is viable. This allows us to compute the gravitational wave (GW) signals arising from the phase transition and discuss the potential discovery prospects of the model at current or future GW experiments. Our global fit places an upper limit on the second scalar mass, the fermion DM mass and the scalar-fermion DM coupling. We also show that the GW spectra of viable points are often within reach of future GW experiments such as LISA, DECIGO and BBO.

Speaker: Mr Ankit Beniwal (Oskar Klein Centre, Stockholm University)

Poster Poster

Slides Slides

11:30 Axions from Strings: the Attractive Solution

The axion solution to the strong CP problem also provides a natural dark matter candidate. If the PQ symmetry has ever been restored after inflation, topological defects of the axion field would have formed and produced relic axions, whose abundance is in principle calculable. Using numerical simulations I will present a detailed study of the evolution of axion strings and the resulting spectrum of axion produced. The features found are important for a correct estimate of the total DM abundance. Work to appear in collaboration with Edward Hardy and Giovanni Villadoro

Speaker: Mr Marco Gorghetto (SISSA)

Slides axionStringPoster.pdf axionString.pptx

11:35 Dark matter axion search experiments using 18T HTS magnet at CAPP/IBS in KAIST

The presence of dark matter had profound consequences on the evolution of the Universe. The Standard Model does not accommodate a suitable dark matter candidate. Therefore, the existence of dark matter is a crucial phenomenological evidence for physics Beyond the Standard Model. The pressing goal of current and future dark matter experiments is to answer the question of whether dark matter interacts with normal matter other than gravity; i.e. if dark matter is detectable. Among the plethora of dark matter candidate particles, the Weakly Interacting Massive Particles (WIMPs) and the Axions are the most outstanding contender. In this talk, we will discuss about the dark matter axion search projects at the Center for Axions and Precision Physics Research at CAPP/IBS in KAIST, especially focused on the CAPP18T axion dark matter search experiment which utilizes a 18T High Temperature Superconducting solenoid magnet, resonant cavity, dilution refrigerator and linear amplifier system.

Speaker: Dr Jingeun Kim (Center for Axion and Precision Physics Resarch, Institute for Basic Science)

Slides jkim16

11:40 Numerical Simulation of the Axion Field through the QCD Phase Transition

We perform a full (3+1)-dimensional numerical simulation of the axion field around the QCD epoch. Our aim is to fully resolve large dynamical non-linear effects in the inhomogenous axion field. These effects are important as they lead to large overdensities in the field at late times. Those overdensities will eventually evolve into axion minicluster, which have various phenomenological implications like microlensing events. It is therefore important to have a reliable estimate of the number of overdensities and their mass relation.

Speaker: Malte Buschmann (University of Michigan)

Slides talk2.pdf

11:45 Effective Approximation of Electromagnetism for Axion Haloscope Searches

An effective approximation is applied to Maxwell’s equations with an anomalous axion interaction. A new set of Maxwell’s equations acquired from this approximation describes only reacted fields generated by the anomalous interaction. Unlike other approaches, this set of Maxwell’s equations inherently satisfies the boundary condition for haloscope searches. The electromagnetic field solutions are evaluated for both cylindrical and toroidal cavity geometries. A small but non-zero difference between electrically and magnetically stored energies appears in both cases. The difference may come from an anomalous non-dissipating current induced by oscillating axions.

Speaker: Mr Youngeun Kim (IBS/CAPP, KAIST)

Slides PATRAS_POSTER.pdf PATRAS_presentation.pdf

11:50 Velocity effects in dielectric haloscopes

We study the effect of the axion dark matter velocity in the recently proposed dielectric haloscopes, a promising avenue to search for well-motivated high mass (40−400 μeV) axions. We describe non-zero velocity effects for axion-photon mixing in a magnetic field and for the phenomenon of photon emission from interfaces between different dielectric media. As velocity effects are only important when the haloscope is larger than about 20% of the axion de Broglie wavelength, for the planned MADMAX experiment with 80 dielectric disks the velocity dependence can safely be neglected. However, a search experiment using more than $\sim 400$ dielectric disks will suffer from significant systematic uncertainties from the unknown velocity distribution. Conversely, an augmented MADMAX or a second generation experiment would be directionally sensitive to the axion velocity in the event of a discovery, and thus a sensitive measure of axion astrophysics.

Speaker: Mr Alexander Millar (Max Planck Institute for Physics)

Poster Poster_for_DESY_2.pdf

Slides DESY_PATRAS_ALEX_MILLAR.pdf

11:55 Standard Model thermodynamics and primordial gravitational waves

In this talk, we discuss the role of Standard Model thermodynamics in cosmology and identify how it affects the spectrum of primordial gravitational waves. By collecting recent results of perturbative and non-perturbative analysis of thermodynamic quantities in the Standard Model, we obtain the effective degrees of freedom including the corrections due to non-trivial interaction properties of particles in the Standard Model for a wide temperature interval. Applying them to the estimation of the spectrum of gravitational waves originated from inflation, we find that there exist several corrections overlooked in previous studies, and that some of them are relevant to future high-sensitivity gravitational wave experiments. There would also be a potential application of the equation of state in the Standard Model obtained in this work to several other topics in cosmology.

Speaker: Dr Ken'ichi Saikawa (Max Planck Institute for Physics)

Poster patras2018_poster.pdf

Slides patras2018_talk.pdf

12:00 Global network of optical magnetometers for exotic physics search

The global network of optical magnetometers for exotic physics search (GNOME) is currently being set-up internationally. More than 10 highly-sensitive, shielded magnetometers are synchronized via GPS and look for global transient spin-interacting events as a signature for new physics. As a model we consider interactions with axion-like particle domain walls that transverse the Earth. We present the network, discuss its characterization and demonstrate some data Analysis techniques of the recent scienctific runs.

Speaker: Dr Arne Wickenbrock (JGU)

Slides wickenbr@uni-mainz.de

12:05 Magnets for ALPS II at DESY

The procedures used to increase the aperture of HERA dipoles for the ALPS II experiment in preparation at DESY are described. The results achieved up to now for 10 out of the required 20 dipoles for ALPS II are presented as well as the maximum obtained currents of the magnets.

Speaker: Dieter Trines (DESY)

Slides PATRAS_2018_Praesentation_aktuell.pptx poster.pdf

12:10 Axion minicluster power spectrum and mass function

We present a semi-analytical method to calculate the average axion energy density, as well as the power spectrum, from the re-alignment mechanism in a scenario where the Peccei-Quinn symmetry breaking happens after inflation. Furthermore, we develop a modified Press & Schechter approach, suitable to describe the collapse of non-linear density fluctuations during radiation domination. This allows us to make a prediction for the distribution of mass and size of axion miniclusters. The presentation is based on the work published with the arXiv number 1708.04466.

Speaker: Andreas Pargner (Karlsruhe Institute of Technology)

Poster 18patras_minicluster.pdf

Slides 18patras_minicluster_slides.pdf

12:15 Conceptual design of the Superconducting magnet for teh Madmax experiemnt

Madmax (Magnetized Disc and Mirror Axion Experiment) is newly started project aiming to verify the existence of dark matter axions. The experiment takes advantage of the axions ability to generate a weak electric field when immersed in a static magnetic field. In order to operate with the required sensitivity a figure of merit of 100 T2m2 in the experimental volume is necessary. This goal is achieved by taking advantage of superconductivity, which allows manufacturing magnets reaching fields in excess of 16 T. This contribution describes the results of a conceptual design of the Madmax superconducting magnet with particular focus on the optimization of the magnetic design aiming to achieve the figure of merit while using the commercially available and well-developed NbTi technology.

Speaker: Cristian Boffo (Babcock Noell GmbH)

Slides Patras_MMaX_Magnet_Noell_20062018.pptx

12:20 Experimental bounds for a two particle hidden sector with alp and hidden photon

I will introduce a model for the dark sector that contains axion-like particles and hidden photons. In this model, both particles can couple to photons. We provide bounds for the couplings versus the mass, using current results from ALPS-I and PVLAS.

Speaker: Dr Pedro Alvarez (Universidad de Antofagasta)

Slides 20180620_hidden_photon_alp_talk.pdf

12:25 KWISP - Hunting Chameleons with the CAST Experiment at CERN

The KWISP (Kinetic Weakly Interacting Slim Particle) detector is part of the CAST experiment at CERN exploring the dark sector. It utilizes an ultra-sensitive opto-mechanical force sensor for the search for solar chameleons. A chameleon is a hypothetical scalar particle postulated as dark energy candidate, which has a local density-dependent direct coupling to matter. Considering this characteristic a flux of solar chameleons hitting a solid surface at a grazing incidence angle will, under certain conditions, reflect and exert the equivalent of a radiation pressure. To exploit this trait the KWISP sensor consists of a thin and rigid dielectric membrane placed inside a resonant optical Fabry-Perot cavity utilizing an active electrooptical feedback system to keep the laser frequency-locked. The reflection of the chameleons off the membrane surface causes a displacement from its equilibrium position, which again will cause cavity mode frequencies to experience a shift. This shift is then sensed in the feedback correction signal. The sensitivity of the detector is determined by the finesse of the cavity and can be enhanced by exploiting the property of the membrane as a mechanical resonator and cooling it down to sub-K temperatures resulting in a projected force sensitivity as low as ~ 8.0*10^(-18) N/Hz^(1/2), yielding various possible applications for the study of new physics.

Speaker: Justin Baier (University of Freiburg)

Poster Patras_poster_KWISP.pdf

Slides Patras_Workshop_KWISP.pdf

12:30 → 13:30 Lunch at the posters

12:30 Contributions: see previous session

13:30 → 15:35 Plenary presentations

Convener: Oliver Keith Baker (Yale University)

13:30 The status of the Lambda Cold Dark Matter model

I will discuss how the identity of the dark matter is reflected in properties of small galaxies such as the satellites of the Milky Way. I will present a test, base on gravitational lensing, that can unambiguously distinguish between cold dark matter and other possibilities such as sterile neutrino dark matter. This test could, in principle, rule out one or the other.

Speaker: Prof. Carlos Frenk (nstitute for Computational Cosmology, Durham University)

13:50 Cosmological axion field and quark nugget dark matter model

I overview the dark matter model offering a very natural explanation of 3 (naively unrelated) problems in cosmology: the observed relation $\Omega_{\rm DM}\sim\Omega_{\rm visible}$, the observed asymmetry between matter and antimatter in the Universe, known as the ``baryogenesis" problem, and also, the so called "Solar Corona Mystery". In this framework, both types of matter (dark and visible) have the same QCD origin, form at the same QCD epoch, and both proportional to one and the same dimensional parameter of the system, $\Lambda_{\rm QCD}$, which explains how the two, naively distinct, problems could be intimately related, and could be solved simultaneously within the same framework. The 80 years old "Solar Corona Mystery" also finds its natural resolution in this framework. The talk is based on two recent preprints: 1. ``Solar Corona Heating by the Axion Quark Nugget Dark Matter,'' arXiv:1805.01897 [astro-ph.SR], written in collaboration with astro people 2. "New mechanism producing axions and how CAST can discover them" arxiv:1805.05184[hep-ph], written in collaboration with particle physics experimentalists.

Speaker: Prof. Ariel Zhitnitsky (University of British Columbia)

Slides PATRAS-2018.pdf

14:10 Non-minimally coupled scalar dark matter from inflationary fluctuations

It is well known that light scalar fields present during inflation are coherently excited. We show that if the field couples to gravity in a non-minimal way, the fluctuations at large scales are suppressed with respect to the small scales ones. This fact allows for the field excitations to make a sizeable contribution to the energy density of the universe without generating too large isocurvature fluctuations at observable scales. We show that this mechanism could generate all the observable dark matter and study the main cosmological implications of this setup.

Speaker: Mr Gonzalo Alonso Álvarez (Heidelberg University)

Slides Gonzalo_Alonso_Alvarez_Patras_18.pdf

14:30 A Fresh Look at Solar Axions and ALPs using the Nuclear Spectroscopic Telescope Array (NuSTAR)

While the discovery of the Higgs boson at the LHC experimentally confirms the widely successful Standard Model (SM) of particle physics, the theory still falls short of explaining several fundamental features of our Universe. A major shortcoming is the SM’s silence on the nature of Dark Matter (DM). Currently, axions and WIMPs are the leading DM candidates with axions simultaneously addressing an additional weakness of the SM, i.e. its inability to explain why strong interactions do not violate charge-parity symmetry as expected from theory. Non-QCD axions on the other hand appear naturally in extensions of the SM, e.g. string theory. If axions exist, they will be created in great numbers in the solar core by the Primakoff effect, via the interaction of a photon from the core’s radiation field with a virtual photon in a nucleus. By the inverse mechanism, one can generate an X-ray flux beyond the solar core. Extensive ground-based searches, notably the CAST experiment at CERN and the proposed next generation helioscope IAXO, use laboratory magnets for the reverse conversion. We employ a novel approach using solar observations of NASA’s hard x-ray astrophysics mission NuSTAR (Nuclear Spectroscopic Telescope Array) to search for the same process via magnetic fields in the solar corona, which, although weaker than those of laboratory magnets, are much more extensive in scale. We will report on the latest results of our research. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 (LLNL-ABS-751151).

Speaker: Dr Julia Vogel (LLNL)

Slides Patra2018_DESY_jkvogel_NuSTAR_Finalized.pdf

14:50 NA64 searching for hidden sectors at the CERN SPS

NA64 is a fixed target experiment at the CERN SPS to search for hidden sectors. In this talk, we will present our latest results on the search for a new sub-GeV vector gauge boson (A′) mediated dark matter (χ) production. The A′, called dark photon, could be generated in the reaction e−Z→e−ZA′ of 100 GeV electrons dumped against an active target which is followed by the prompt invisible decay A′→χχ. The experimental signature of this process would be a clean event with an isolated electron and large missing energy in the detector. This allows us to set new limits on the γ−A′ mixing strength and constrain models with light thermal dark matter or light scalar, Majorana or pseudo-Dirac thermal dark matter. Preliminary results on the search for the X→e+e− decay of a new light X boson which could explain a recently observed anomaly in the 8Be transitions will be also discussed.

Speaker: Mr Emilio Depero (ETH)

Slides Patras_NA64.pdf

15:10 Status of PICO: Searching for WIMPs with Bubble Chambers

We report on recent results from the PICO program to search for WIMPs using bubble chambers and plans for future experiments. Our most recent results come from the operation of the PICO-60 detector, which operated in the SNOLAB underground laboratory and contained a 52-kg target volume of liquid C3F8 . This chamber exhibits exhibits excellent electron recoil and alpha decay rejection, and the observed multiple-scattering neutron rate indicates a single-scatter neutron background of less than 1 event per month. A blind analysis of an efficiency-corrected 1167-kg-day exposure at a 3.3-keV thermodynamic threshold reveals no single-scattering nuclear recoil candidates, consistent with the predicted background. These results set the most stringent direct-detection constraint to date on the WIMP-proton spin-dependent cross section at 3.4 × 10−41 cm2 for a 30-GeVc−2 WIMP, a factor of 17 improvement over previous results. We are conducting R&D on new type of bubble chamber for WIMP searches that has the potential to scale to very large target sizes. Construction is starting this year on the PICO-500 experiment, which will have an order of magnitude larger target volume than PICO-60.

Speaker: Andrew Sonnenschein (Fermilab)

Slides Powerpoint pptx

15:30 Patras 2019

Speaker: Prof. Marc Schumann (Univertity of Freiburg)

Slides patras2019.pdf

15:35 → 16:00 Coffee break

16:00 → 23:15 Excursion and conference dinner

16:15 1st bus transport to "devils bridge" (Elbe river)

16:45 2nd bus transport to "devils bridge" (Elbe river)

17:15 Harbor boat trip

19:00 Dinner at the brewery "ÜberQuelll"

22:00 1st bus transport back to DESY

22:30 2nd bus transport back to DESY

23:00 3rd bus transport back to DESY

Thursday 21 June

09:00 → 09:35 WIMP Searches 2018

This talk will summarize the current status of direct WIMP searches, from old time favorites such as liquid xenon experiments to new ideas which are pushing our technologies into the sub-GeV mass range.

Speaker: Rafael Lang (Purdue University)

Slides rafael_wimpdetection.pdf

09:35 → 10:55 Plenary presentations

Convener: Geraldine Servant (DESY and U. hamburg)

09:35 PandaX status and prospect

The PandaX dark matter experiment searches for Weakly interacting massive particles (WIMPs) in the China Jinping Underground Laboratory (CJPL). PandaX-II, with a 580-kg liquid xenon TPC currently under operation, is one of the leading WIMP direct detection experiments. In this talk, I will present an overview of the project, discuss recent results from PandaX-II, and give an outlook into the future.

Speaker: Dr Pengwei Xie (Tsung-Dao Lee Institute)

Slides PandaX_PATRAS_2018.pdf

09:55 Bose Condensation by Gravitational Interactions

We study Bose condensation and formation of Bose stars in the virialized dark matter halos/miniclusters by universal gravitational interactions. We prove that this phenomenon does occur and it is described by kinetic equation. We give expression for the condensation time. Our results suggest that Bose stars may form in the mainstream dark matter models such as invisible QCD axions and Fuzzy Dark Matter.

Speaker: Dmitry Levkov (Institute for Nuclear Research RAS)

Slides Bose star formation - movie talk.pdf

10:15 Search for solar chameleons with a GridPix detector at the CAST experiment

Dark Energy can be explained by modifying General Relativity introducing a new scalar field with a coupling to matter. To avoid unnatural effects, a screening mechanism can be utilized. In case of the chameleon screening this gives rise to a new particle, the chameleon, featuring an effective mass depending on the local energy density as well as an effective coupling to photons. Chameleons can be produced similar to axions by converting photons inside strong electromagnetic fields through the Primakoff effect. Therefore the Sun can act as a chameleon source and axion helioscopes such as the CERN Axion Solar Telescope (CAST) can be utilized as chameleon helioscopes. In contrast to axions, chameleons are produced not in the solar core but in the tachocline, a region of high differential rotation inside the Sun providing strong magnetic fields. Therefore the X-ray photons resulting from solar chameleons (re)converting to photons inside a helioscope are in the energy range of below 2 keV, thus requiring X-ray detectors sensitive to low energy X-ray photons for a solar chameleon search with an axion helioscope. In October 2014 a low energy X-ray detector developed at Bonn was installed behind one of the X-ray telescopes of CAST. This detector utilizes a 'GridPix' device, a Micromegas stage created on top of a pixelized readout ASIC by means of photolithographic postprocessing. Due to the readout's high granularity, this technology allows for an energy threshold of a few hundred eV and in addition for a topological background suppression resulting in background rates of less than $10^{-4}\,\mathrm{/keV/cm²/s}$ below 2 keV. After successful operation until December 2015 the recorded data has been analysed. With respect to CAST's previous search for solar chameleons using a silicon drift detector, the sensitivity to the chameleon photon coupling could be increased by a factor of two for the first time allowing to probe the parameter space below the solar luminosity bound.

Speaker: Christoph Krieger (University of Bonn)

Slides hamburg2018patras-ws.pdf

10:35 Dark Matter implications of DAMA/LIBRA-phase2 results

This presentation will examine the dark matter interpretation of the DAMA/LIBRA-phase 2 results. Canonical spin-independent, isospin violating spin-independent and spin-dependent interactions will all be discussed.

Speaker: Prof. Chris Kelso (University of North Florida)

Slides PATRAS-2018-Kelso.pdf

10:55 → 11:30 Coffee break

11:30 → 13:10 Plenary presentations

Convener: Dr Claudio Gatti (INFN)

11:30 The Storage-Ring proton EDM potential sensitivity to the axion dark matter background field

The axion dark matter background field can induce electric dipole moment (EDM) oscillations to nuclei via its coupling to the gluon fields. The frequency of oscillations corresponds to the axion mass. The amplitude of the oscillation is at the $10^{-34}$ $e\cdot$cm level for the standard local dark matter density, and it is proportional to the square root of its value. The storage ring EDM method is designed to probe the proton and deuteron permanent (DC) EDM at the $10^{-29}$ $e\cdot$cm level by freezing the spin direction along the momentum direction of a longitudinally polarized beam in a storage ring. Nonetheless, it can also be sensitive to the oscillating EDM by running the experiment so that the particle $g-2$ frequency coincides with the axion oscillation frequency. It turns out that the systematic errors are easier to handle than in the frozen spin EDM method and for the higher frequency range the sensitivity can be much larger. I will explain the details of the method and its prospects.

Speaker: Prof. Yannis Semertzidis (CAPP/IBS and KAIST)

Slides YkS_Patras2018_Axion_EDM_2018_0621.ppt

11:50 The mass of the neutrino - truly

Precision measurements of the kinematics of the weak beta decay processes are a model independent and direct approach to determine the absolute neutrino mass. This presentation reviews the current status of direct neutrino mass searches. The KArlsruhe TRItium Neutrino experiment (KATRIN) is commencing data taking and will be discussed in detail. Future experiments and prospects to detect spectral features from beyond standard model particles and effects will be assessed.

Speaker: Klaus Helbing (University of Wuppertal)

Slides KATRIN-PATRAS-2018-Helbing_v2.pdf

12:10 Exploring high mass regions for axion dark matter at IBS/CAPP

The Center for Axion and Precision Physics Research (CAPP) of the Institute for Basic Science (IBS) in Korea has completed the construction of the infrastructure for axion dark matter search experiments. An experiment utilizing a 9 T superconducting magnet with a 127 mm bore diameter placed in a He-3 cryogenic system is currently under preparation. This experiment will employ a new cavity design, dubbed ‘pizza-cylinder cavity’, which provides various benefits in searching for high frequency axion dark matter. We desire to probe a broad frequency range of 2.8 to 7.0 GHz (equivalent axion mass range of roughly 10 to 30 μeV) with a target sensitivity of 10 times KSVZ. We present the status of the experiment and discuss the future prospects.

Speaker: SungWoo YOUN (CAPP/IBS)

Slides Patras2018_YOUN.pptx

12:30 Completion of Phase I and Preparation for Phase II of the HAYSTAC Experiment

The Haloscope At Yale Sensitive To Axion CDM (HAYSTAC) utilizes a tunable resonant microwave cavity to search for dark matter axions. In this talk, we will present an overview of the operational details and results from Phase I of the HAYSTAC experiment. This phase relied on a 9.4 T magnet, Josephson parametric amplifiers, and a dilution refrigerator for the operation of the experiment. Axion models with two photon coupling $g_{a\gamma\gamma}\geq 2\times 10^{-14}\ \text{GeV}^{-1}$ were excluded in the $ 23.15 < m_a<24.0\ \mu\mathrm{eV}$ mass range. Improvements for Phase II of the experiment will also be presented, which include upgrades to the cryogenics system, a new squeezed-state receiver system. Finally, work on multi-rod cavities and photonic band gap resonators for higher frequency operation will be discussed. This work was supported by the National Science Foundation, under grants PHY-1362305 and PHY-1607417, by the Heising-Simons Foundation under grants 2014-181, 2014-182, and 2014-183, and by the U.S. Department of Energy through Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Nicholas Rapidis is supported by the Haas Scholars Program.

Speaker: Nicholas Rapidis (UC Berkeley)

Slides Rapidis_Patras.pptx

12:50 The ORGAN Experiment

We discuss the current status of the ORGAN experiment, a high mass axion haloscope. The goal of ORGAN is to search the promising high axion mass regime, covering the range of masses proposed by the SMASH model. This talk will include a review of progress and results to date, then cover developments in cavity design and R&D, and the next science run of the primary haloscope experiment. Cavity R&D builds on our work on tunable super-mode dielectric resonators [1], with applications to the high-mass regime. These resonators can be designed to have scan rates improved by 1 to 2 orders of magnitude over traditionally tuned haloscope resonators. The plans for the next experiment, which will operate in a new dedicated dilution refrigerator with a base temperature of 7 mK and a 14 T superconducting solenoid, will be discussed. We will also give an overview of some complementary experiments that are under development at UWA to operate alongside ORGAN, including wide mass range searches for axion-like particles. 1. Ben T. McAllister, Graeme Flower, Lucas E. Tobar, Michael E. Tobar, “Tunable Super-Mode Dielectric Resonators for Axion Haloscopes”, Phys. Rev. Applied 9, 014028 (2018)

Speaker: Mr Ben McAllister (University of Western Australia)

Slides McAllister2018.pdf

13:10 → 14:30 Lunch break

14:30 → 15:50 Plenary presentations

Convener: Prof. Gondolo Paolo (University of Utah)

14:30 Radio-line signatures from conversion of axion-like particles to photons

Axion-like particles (ALPs) can convert into photons in several different ways: in an external magnetic field (known as the Primakoff effect), by decay into two photons, or through parametric amplification of incoming radio photons in an oscillating ALP field within a narrow frequency range. For non-relativistic ALPs all three effects can give rise to radio lines, in particular from astrophysical objects with strong magnetic fields or from regions with ALP over-densities, such as ALP stars. We give a short overview over estimated intensities and prospects for detectability of such radio lines.

Speaker: Prof. Guenter Sigl (University of Hamburg)

Slides haloscopes.pdf

14:50 Constraints On Bosonic Dark Matter From Ultralow-Field Nuclear Magnetic Resonance (CASPEr)

The nature of dark matter, the invisible substance that makes up over $80$% of the matter in the universe, is one of the most intriguing mysteries of modern physics. Elucidating the nature of dark matter would profoundly impact our understanding of cosmology and particle physics, providing key insights into physics beyond the Standard Model. Recent theories of couplings between dark matter and nuclear spins have opened the possibility of directly detecting axion, axion-like and dark-photon dark matter via NMR spectroscopy [1]: as nuclear spins move through the galactic dark-matter halo, the spins couple to dark-matter particles and behave as if they were in an oscillating magnetic field, potentially generating a dark-matter-driven NMR signal. The Cosmic Axion Spin Precession Experiment (CASPEr) is multi-faceted NMR search for such particles [2]. Here, we will review a CASPEr experiment based on zero- to ultralow-field NMR (ZULF NMR [3]). We first review the physical principles enabling the detection of dark-matter via ZULF NMR and introduce the off-resonance-based measurement scheme used for such detection [4]. We expect dark-matter particles to induce modulation of the $J$-coupling energy levels of the NMR sample. Axions and dark-photons could then be detected by searching for frequency-modulation induced sidebands in the well-defined ZULF NMR spectrum of labelled formic acid. We then describe the current ZULF NMR apparatus and present an exotic data processing scheme, which enables the possibility to perform coherent averaging of transient NMR signals induced by sources of unknown frequencies such as dark matter. Finally, we present our latest results on ultralight-axion dark-matter acquired through this search. [1] P. W. Graham and S. Rajendran, Phys. Rev. D, (88), 035023 (2013) [2] D. Budker et al., Phys. Rev. X, (4), 1-10 (2014) [3] J.W. Blanchard, D. Budker, eMagRes, (5), 5-3 (2016) [4] A. Garcon et al., IOP Quantum Science and Technology, (3), 1 (2017)

Speaker: Mr Antoine Garcon (Helmholtz Institute Mainz)

Slides CASPEr-ZULF-Results

15:10 Proposal of new LHC searches for ALPs

ALPs that couple to gluons are predicted both to solve the strong CP problem as well as in composite Higgs models (Higgs pseudo-Goldstone partners) and in Supersymmetry (R-axion). I will discuss unexplored avenues in the LHC phenomenology resulting from such gluon-ALP couplings. I will derive a new LHC bound on ALPs from diphoton cross-section measurements, and show it is the strongest existing limit in the mass window 10-65 GeV. I will then propose new ALP searches at ATLAS, CMS and the LHCb.

Speaker: Filippo Sala (DESY Hamburg)

Slides FSala_PATRAS18.pdf

15:30 Search for dark matter in the form of axion-like particles and hidden photons in the XMASS detector

XMASS is an experiment to search for dark matter (DM) using a single-phase liquid-xenon scintillator at the Kamioka Observatory in Japan which is located 2700 m.w.e. underground. With its low background environment, the XMASS detector has sensitivity not only for standard WIMPs which produce a xenon nuclear recoil in the detector, but also for various types of DM, for example, DM inducing an electron recoil. In this talk, we will report results of searches for axion-like particles and hidden photons as candidates for cold DM. These bosons are expected to induce an electron recoil through an interaction analogous to photoelectric effect with a xenon atom. Analysing 800 live-days of XMASS data with 327 kg liquid xenon in the fiducial volume, we set most stringent upper limits on the coupling constant $g_{Ae}$ of axion-like particles and the parameter for kinetic mixing $\alpha’/\alpha$ of hidden photons in the mass range from 40 to 120 keV/$c^2$.

Speaker: Dr Kazufumi Sato (ICRR, The University of Tokyo)

Slides 180621-sato-AxionWIMP2018-draft-XMASS.pdf

15:50 → 16:20 Coffee break

16:20 → 17:30 Plenary short presentations

Convener: Prof. Peter Quinn (ICRAR)

16:20 Resonant and broadband haloscope searches for hidden photon dark matter using the HERA resonant cavity at frequencies below 500 MHz

The microwave cavity experiment WISPDMX is a haloscope type experiment sensitive to hidden photon and possible light dark matter candidates in a wide mass range below 2 $\mu$eV. The flexible broad-band read-out of WISPDMX provides simultaneous sensitivity to multiple resonant modes as well as to off-resonant frequencies corresponding to particle masses as low as $\sim 10^{-12}$ eV. After completing the construction of a fully tunable WISPDMX setup, the first science run was carried out from 23rd October 2017 to 2nd November 2017 and accumulated a total acquisition time of 61.1 hours with the lowest detectable power of $\sim 10^{-18}$ Watt and sensitivity of $\chi \sim 10^{-14}$ to kinetic mixing of hidden photon dark matter. In this talk, we will present the general developments and the first results from WISPDMX.

Speaker: Mr Le Hoang Nguyen (Uni Hamburg)

Poster Le_Hoang_Nguyen_Poster_-__Patras_2018.pdf

Slides Le_Hoang_Nguyen_Slide_-_Patras_2018.pdf

16:25 Simulation studies for the MADMAX Axion direct detection experiment

Axions are hypothetical particles introduced to solve the strong CP problem of the Standard Model. In addition axions can resolve the dark matter mystery. Axions with masses in the range of a few tens of µeV up to a few hundreds of µeV are furthermore motivated by the scenario in which the Peccei-Quinn symmetry is broken after inflation. This motivates the development of new techniques to become sensitive to this specific axion mass region, which cannot be explored with existing direct axion dark matter experiments. One option is the dielectric haloscope, which utilizes dielectric media and a 10 T magnet to enhance the signal of photon converted axions. This talk will focus on the simulation of the MADMAX dielectric haloscope. The MADMAX prototype experiment is expected to be operated at DESY 2019-2021.

Speaker: Mr Jan Schütte-Engel (Uni Hamburg)

Slides Patras2018_SchuetteEngel.pdf poster_patras_SchuetteEngel.pdf

16:30 Search for Axion Dark Matter in a Mass Range of 6.62 to 7.04 μeV with a Tunable Microwave Resonant Cavity

Since P. Sikivie had introduced an experimental technique for detection of the axion dark matter with a microwave resonant cavity, a number of experiments have attempted to search for it using this haloscope technique in various mass ranges, but no axion signal has been seen so far. Although those excluded mass regions with certain sensitivities in terms of axion-photon coupling constant ($g_{a\gamma\gamma}$), broad mass regions still need to be explored with a good sensitivity. To unveil one of those regions, a yet another attempt to search a mass range of 6.62 to 7.04 $\mu$eV is being made at IBS/CAPP employing a new locomotive frequency tuning mechanism. The experiment aims the most sensitive axion dark matter search in this axion mass range, where the sensitivity could reach the QCD axion band. In this presentation, the configurations and technical details of the experiment are discussed.

Speaker: Dr Soohyung Lee (IBS/CAPP)

Slides Slides_SoohyungLee.pdf

16:35 Status of the Cosmic Axion Spin Precession Experiment (CASPEr)

The Cosmic Axion Spin Precession Experiment (CASPEr) is a multi-faceted research program using nuclear magnetic resonance (NMR) techniques to search for dark-matter-driven spin-precession. CASPEr is naturally divided into two main research directions, based on two possible couplings to the Standard Model. - CASPEr-Wind searches for spin precession induced by the coupling between ultralight bosons and the axial nuclear current (the so-called ``axion wind'' coupling). The interaction that drives the spin precession may be treated as a pseudo-magnetic field where the nuclear spin couples to the relative momentum of the local dark matter field. - The coupling of axions to the gluon field of quantum chromodynamics (QCD) is explored by CASPEr-Electric, which searches for the effect of an oscillating nuclear electric dipole moment. In the presence of an electric field, this electric dipole moment generates a toque that drives spin precession. The combined experiment searches for dark matter composed of axions, axion-like particles, or dark/hidden photons with boson masses from $\sim 6\times 10^{-17}$ to $\sim 6\times 10^{-7}$ eV. We will report on the current status and describe recent progress in the construction of the assorted CASPEr apparatus.

Speakers: Dr John Blanchard (Helmholtz-Institut Mainz), Marina Gil (Mrs.)

Poster https://files.slack.com/files-pri/TARL1DS9H-FB7TNRLTW/casper_overview_2018-150dpi-01.png

Slides NMR_Meets_Dark_Matter.pdf NMR_Meets_Dark_Matter.ppt

16:40 Status report of the QUAX R&D activity

The QUAX project is an R&D activity aimed at demonstrating the feasibility of an axion haloscope exploiting the axion electron coupling. To this end, a ferrimagnetic material is coupled to a microwave resonant cavity and a sensitive detector looks for excess power released into the system by an axion wind. In this talk I will present the latest results obtained by the QUAX collaboration in the last year, including the performances of a small scale prototype of a complete detector. Limits on the axion electron coupling, though very weak, are given for an axion mass of about 58 microeV. These limits are the first of this type obtained by using an haloscope.

Speaker: Dr Claudio Gatti (INFN - LNF)

Slides QUAX_PATRAS2018_Gatti.pdf

16:45 Laser effect for cosmic axions

We study parametric resonance of photons in cosmic Bose stars formed by light bosonic (axion-like) dark matter. We argue that this effect may lead to powerful bursts of maser radiation during the Bose star collapse or its collision with compact astrophysical object like black hole or neutron star. This may explain fast radiobursts (FRB) and some other observational anomalies.

Speaker: Dr Alexander Panin (INR RAS, Moscow)

Poster poster_v5.pdf

Slides talk.pdf

16:50 New results on the anomalous transparency of the Universe for very-high-energy gamma rays

Unphysical distance dependence in convex features of deabsorbed blazar spectra (upward breaks), reported in 2014, suggested incorrect model of absorption of E>100 GeV gamma rays due to e+e- pair production on the extragalactic background light (EBL). We present results of the new study aimed to review previous findings, making use of an updated clean source sample, new gamma-ray data and most recent absorption models.

Speaker: Alexandr Korochkin (INR RAS)

Slides PatrasPoster.pdf PatrasPresent.pdf

16:55 Introduction to the RADES project at CAST, an axion detector using microwave filters

The Relic Axion Detector Experimental Setup (RADES) is an axion search project that uses a microwave filter as a detector. This type of filters allow the search for dark matter axions of masses in the decade 10-100 $\mu$eV. This presentation will focus on the proposal, design, construction and first tests of the RADES microwave filter. The filter consists of 5 stainless steel sub-cavities joined by rectangular irises. The size of the sub-cavities determines the working frequency, the amount of sub-cavities determine the working volume. A theoretical model was built in order to describe the detection properties of the cavity. Simulations were done to establish the optimal design of the microwave filter. The first cavity prototype was built to work at a frequency of $\sim$ 8.4 GHz and it was placed at the 9 T CAST dipole magnet at CERN. A description of the theoretical framework, the simulations, the construction, the data acquisition system and some preliminary results of the electromagnetic properties of the cavity are going to be presented. The results show the potential of this type of filter to reach QCD axion sensitivity at X-Band frequencies.

Speaker: Sergio Arguedas Cuendis (CERN)

Slides Presentation-Introduction_to_the_RADES_project_at_CAST.pdf

17:00 Constraints on Axion-Like Particles from X-ray Point Sources

Axion-like particles (ALPs) can induce localised oscillatory modulations in the spectra of photon sources passing through astrophysical magnetic fields. Chandra and Persesus observations of quasars or AGNs located in or behind galaxy clusters represent a dataset of extraordinary quality for ALP searches. We use this dataset to search for X-ray spectral irregularities in the point source spectra. The absence of irregularities allows us to place leading constraints on the ALP-photon mixing parameter $g_{a\gamma\gamma} < 10^{-12}$ GeV$^{-1}$ at 95% confidence for ALP masses $m_a < 10^{-12}$ eV. We also comment on expected bounds from future missions such as Athena.

Speaker: Dr Markus Rummel (Perimeter Institute / McMaster University)

Slides AxionWimp2018_5minTalk.pdf

17:05 Heterodyne detection in ALPS II

The ALPS II experiment searches for axion-like particles (ALPs) using the “light shining through a wall” technique. The collaboration is currently developing two different detection methods both targeting sensitivities to photon levels as low as a few photons per week. One approach, based on photon counting, uses a Transition Edge Sensor while the other involves heterodyne interferometry. Heterodyne detection takes advantage of the coherent nature of the regenerated photon signal. However, it also relies on the ability to track precisely the phase of the expected signal with a precision better than 0.1 cycles over integration times of several weeks. I will report on the design and measurements of the planned heterodyne optical setup.

Speaker: Dr Giuseppe Messineo (University of Florida)

Poster HET_for_ALPSII-poster.pdf

Slides HET_for_ALPSII-Messineo.pdf

17:10 Velocity dependence of dark matter annihilation for indirect detection.

The p-wave annihilation of the dark matter particle has recently gained wider interest. Generically, the expected annihilation cross section estimated from the required relic density is considerably smaller than the value of < \sigma v >≈ 3.0*10^{-26}cm^{3}s^{-1}) for a pure s-wave annihilation channel scenario. In this work, we provide expected annihilation rates from the dynamics of dSphs galaxies and galaxy clusters using the N-dimension Particle Swarm Optimization (PSO) scanning method. We introduce and calculate a velocity-dependent J-factor, which in turn allows us to find the effective annihilation cross section for different interactions. The result demonstrates that a family of WIMP-type dark matter models exist, which can not be detected in indirect searches. In specific cases however, Sommerfeld enhancement could boost the annihilation by a sufficiently large factor to become observable again. We finally consider additional and recent constraints from direct dark matter search experiments.

Speaker: Mr Chao Zhang (Institut für Experimentalphysik, Univetsitaet Hamburg)

Slides PATRAS2018_talk_ChaoZhang.pdf

17:15 Precision Frequency Measurement Approach to Axion Detection

We propose a new approach to axion detection based on precision frequency measurements as opposed to the traditional power detection approach. The approach utilises a high Quality Factor cavity supporting two mutually orthogonal modes. We demonstrate how axion modified Maxwell equations lead to either a beam splitter or parametric interaction terms in the axion up- or downconversion cases respectively. The term couples two modes of different frequencies with the axion frequency (mass) being either the difference (upconversion) or sum (downconversion) of the frequencies of the modes. The derivation introduces a unitless two-mode geometric coefficient characterising the coupling between two particular modes. The Hamiltonian term in the rotating wave approximation is propositional to axion complex amplitude and the axion-photon coupling constant. The double mode cavity could be used for the traditional power detection when one or both modes are strongly pumped. Although such a method would be inefficient compared to the common DC magnet technique. On the other hand a possibility to employ a highly sensitive cross correlation technique may lead to comparable results. Instead of measuring tiny amounts of power deposited in the cavity modes, we propose to measure frequency shifts associated with the axion coupling Hamiltonian terms. Based on the equation of motion of axion coupling modes, we calculate frequencies shifts of the modes that can be observed with one of a few frequency control techniques. We predict both real and imaginary parts of the resonance frequency to be sensitive to axions depending on the type of coupling. In our work, we consider a double oscillator approach. We consider a simple cavity architecture based on a copper cylindrical cavity and TM020 and TE011 modes. The TM020 mode is at 9 GHz, and the TE011 mode is tunable in the 6-9 GHz range. Both modes have Quality factors on the order of 5,000-10,000. Mode overlap coefficients are on the order of unity. Building a loop oscillator based on this cavity would allow axion sensitivities approaching popular axion model bands. The power of the new approach relies on the fact that unlike in the power detection method where the sensitivity is limited by the thermal (or quantum) noise in the readout, the frequency sensing is limited by resonator linewidths and their internal fluctuations. For modern cryogenic resonators, Quality factors exceed 109 giving fractional frequency stability better than 10-16 have been demonstrated. If implemented, such systems could exclude axion-photon couplings below the predicted DFSZ coupling.

Speaker: Dr Maxim Goryachev (University of Western Australia)

Paper http://arxiv.org/abs/1806.07141

Poster AxionWIMP-2018.pdf

Slides goryachev_2018.pdf

17:20 Experimental Status of the Cosmic Axion Spin Precession Experiment (CASPEr-Wind)

The Cosmic Axion Spin Precession Experiment (CASPEr), particularly the CASPEr-Wind, is a detection scheme searching for particles with a coupling to nuclear spin; some examples being dark matter candidates like the axion/axion-like particles, hidden photons, or any pseudo-Goldstone boson [1,2,3]. The coupling induces precession of the nuclear spin about the axion momentum which will be detected using nuclear magnetic resonance (NMR) techniques. In this talk, current experimental progress will be presented for the various components involved. The sample for CASPEr-Wind is hyperpolarized liquid xenon, which preparation of is a critical part of the experiment. We will report on our spin-exchange optical pumping cell, unique in design, for the hyperpolarization of gaseous xenon including it's accompanying diagnostics. The hyperpolarized xenon is condensed in a spherical sapphire cell held at liquid temperature inside of a superconducting magnet within the `variable temperature unit' probe (VTI). This VTI utilizes temperature controlled nitrogen gas and insulation to maintain the $\sim$170 K differential. We will discuss it's design and prototyping, including initial tests of our superconducting quantum interference devices (SQUIDs) used to detect the NMR signal induced by the dark matter. [1] D. Budker et al., Phys. Rev. X 4, 021030 (2014). [2] P. W. Graham and S. Rajendran, Phys. Rev. D 88, 035023 (2013). [3] P. W. Graham et al., Annu. Rev. Nucl. Part. Sci. 65, 485–514 (2015).

Speakers: Mr Gary Centers (Johannes Gutenberg Universitaet), Mr Nataniel Figueroa (Johannes Gutenberg Universitaet)

Poster Figueroa_Centers_Poster_PrintInA0.pdf

Slides CentersSlides_PATRAS2018.pdf

17:25 Axion Isocurvature Perturbations in Low-Scale Models of Inflation

Quantum fluctuations of the axion field during inflation easily result in dark matter isocurvature perturbations that exceed the upper bound from observations of the cosmic microwave background. This problem is solved in models of low-scale inflation where axion fluctuations are suppressed by the small value of the Hubble rate. In this talk, I review the resulting constraints on models of low-scale inflation in supergravity. I focus on different supergravity models of hybrid inflation and demonstrate how the nonobservation of axion isocurvature perturbations can be used to derive useful bounds on the gravitino mass. This results in testable relations between the physics of axion dark matter and the spontaneous breaking of supersymmetry in the hidden sector.

Speaker: Dr Kai Schmitz (MPIK Heidelberg)

Poster patras_2018_poster_kai_schmitz.pdf

Slides patras_2018_talk_kai_schmitz.pdf

17:30 → 18:30 Drinks at the posters

17:30 Contributions: see previous session

Friday 22 June

09:00 → 09:35 Dark matter axion mass

Speaker: Dr Javier Redondo Martin (Zaragoza U / MPP Munich)

Slides mypres.pdf

09:35 → 11:15 Plenary presentations

Convener: Joerg Jaeckel (ITP Heidelberg)

09:35 Probing axion-photon coupling from the resonant conversion of QCD axion and ALP dark matter

We have revisited the resonant conversion of the QCD axion and an axion-like particle (ALP), where the condition of the level crossing between the QCD axion and ALP is strictly defined. We perform the numerical calculations to comoving axion numbers, by which the adiabatic condition of the resonant conversion of the QCD axion and ALP is revised. We find a parameter space where the ALP can contribute to the right amount of dark matter relic abundance, and its decay constant can be much smaller than the one associated with the QCD axion. As a consequence, the axion coupling to photons can be enhanced by about a factor of 10 -100, which could be probed potentially by the undergoing and future-operating axion detection experiments.

Speaker: Mr Shu-Yu Ho (Tohoku University, Japan)

Slides Axion_Wimps_2018_SYH.pdf Axion_Wimps_2018_SYH.pptx

09:55 Searches for Dark Matter beyond the WIMP with SuperCDMS Technology

The Super Cryogenic Dark Matter Search (SuperCDMS) is a direct Dark Matter search experiment designed to observe nuclear recoils induced by WIMPs. However, it is also sensitive to Dark Matter particle candidates beyond the standard WIMP paradigm, which could create electron recoil signals in the cryogenic silicon and germanium detectors. The pool of candidates is rich and includes light Dark Photons, light Axions and sub-GeV WIMP-like particles. This talk will give an overview of the respective interaction channels, and will highlight first search results using a new generation SuperCDMS detector with single electron-hole-pair resolution. The talk will also discuss the prospects of searches for Dark Matter beyond the WIMP with the upcoming SuperCDMS SNOLAB experiment.

Speaker: Dr Belina von Krosigk (University of British Columbia)

Slides 2018_PATRAS_BvKrosigk.pdf

10:15 Optical Ring Cavity Search for Axion Dark Matter

We propose a novel experiment to search for axion dark matter which differentiates the phase velocities of the left and right-handed polarized photons. Our optical cavity measures the difference of the resonant frequencies between two circular-polarizations of the laser beam. The design of our cavity adopts double-pass configuration to realize a null experiment and give a high common mode rejection of environmental disturbances. We estimate the potential sensitivity to the axion-photon coupling constant gaγ for the axion mass m≲10−10 eV. In a low mass range m≲10−15 eV, we can achieve gaγ≲3×10−16 GeV−1 which is beyond the current bound by several orders of magnitude.This presentation is based on our recent paper https://arxiv.org/abs/1805.11753 .

Speaker: Dr Ippei Obata (ICRR, University of Tokyo)

Slides Obata_Patras18.pdf

10:35 The status of supersymmetry by GAMBIT

Is supersymmetry losing ground as a compelling extension of the Standard Model? Or is there still enough experimental evidence to support our faith in it? In search of quantitative answers, I review the latest GAMBIT results for various supersymmetric models covering the CMSSM, NUHM1 and 2, MSSM7 and MSSM9.

Speaker: Csaba Balazs (Monash University)

Slides DM_by_GAMBIT.pdf

10:55 Update on the LUX/LZ experiments

The Large Underground Xenon (LUX) experiment operated at the Sanford Underground Research Facility from 2013 to 2016. The detector was instrumented as a dual-phase xenon time projection chamber (TPC), providing energy measurement, position information in 3D, and single-scatter event identification. After decommissioning the instrument, the collaboration continues to exhaustively exploit the existing calibration and WIMP-search data aiming for a better understanding of the Liquid Xenon (LXe) physics and also to perform searches of dark matter candidates beyond the standard WIMP paradigm. For WIMPs, a profile likelihood analysis using a total exposure of $129\,\text{kg.yr}$ (runs $3+4$) set a $90$% CL upper limit on the spin-independent (SI) cross section of $1.1\times10^{-46}\,\text{cm}^{2}$ at $M_{WIMP}=50\,\text{GeV.c}^{-2}$. For spin-dependent (SD) interactions, cross sections above $\sigma_{n}^{SD}=1.6\times10^{-41}\,\text{cm}^{-2}$ ($\sigma_{p}^{SD}=5\times10^{-40}\,\text{cm}^{2}$) are also excluded at $M_{WIMP}=35\,\text{GeV.c}^{-2}$ ($90$% CL). For axion and axion-like particles, a double-sided profile likelihood analysis using an exposure of $38.4\,\text{kg.yr}$ (run $3$ only) excluded $g_{Ae}$ larger than $3.5\times10^{-12}$ ($90$% CL) for solar axions. This limit on the coupling corresponds to an upper limit on the axion mass of $0.12\,\text{eV.c}^{-2}$ or $36.6\,\text{eV.c}^{-2}$, depending on the theoretical model assumed. For galactic axion-like particles, values of $g_{Ae}$ larger than $4.2\times10^{-13}$ are excluded for particle masses in the range $1-16\,\text{keV.c}^{-2}$. These are the most stringent constraints to date for these interactions. Besides detailing the calibrations and analysis leading to the LUX results, we will also present the LUX-ZEPLIN (LZ) detector, a LXe dark matter detector featuring more than $5\,\text{tons}$ of target material in the fiducial region (from a total of $10\,\text{tons}$ of xenon). It will be installed at the same facility used by LUX. With a projected exposure of $1000\,\text{days}$ (commissioning starts in 2020), LZ aims to exclude the WIMP-neutron (-proton) SD cross-sections down to $2.7\times10^{-43}\,\text{cm}^{2}$ ($8.1\times10^{-42}\,\text{cm}^{2}$) for a $40\,\text{GeV.c}^{-2}$ WIMP. For the WIMP-nucleon SI interactions, a best sensitivity of $1.6\times10^{-48}\,\text{cm}^{2}$ ($90$% CL, $M_{WIMP}=40\,\text{GeV.c}^{-2}$) is expected. This represents a factor of $10$ improvement when compared to the expected sensitivities of currently running LXe dark matter experiments.

Speaker: Dr Francisco Neves (LIP - Laboratorio de Instrumentacao e Fisica Experimental de Particulas)

Slides LUX-LZ-PATRAS2018-FNeves.pdf

11:15 → 11:45 Close-out

11:45 → 12:45 Farewell coffee

14:00 → 16:00 DESY-Tour: (with registration only)