Particle Physics Challenges

25 Sept 2018, 12:45 → 28 Sept 2018, 14:00 Europe/Berlin

Main Auditorium (DESY Hamburg)

The annual DESY Theory Workshop is organized by the elementary particle physics community in Germany. The focus is on a topical subject in theoretical particle physics and related fields. This year workshop will have a focus on particle phenomenology. More details can be found on the conference homepage https://th-workshop2018.desy.de

The workshop features:

• Four half-day plenary sessions of specialized talks by invited speakers.
• Two half-days of parallel sessions, allowing young researchers to present their work (on Wednesday and Thursday afternoons).
• The DESY Heinrich-Hertz-Lecture on Physics for public outreach (on Thursday evening).

Tuesday, 25 September

12:45 → 13:50 Registration

13:50 → 14:00 Welcome

13:50 Welcome

Speaker: Christophe Grojean (DESY)

Slides Welcone_slides_TH2018.pdf

14:00 → 16:00 Plenary Session

Convener: Michael Kraemer

14:00 Gravitational waves and particle physics

Speaker: Alfredo Urbano

Slides Urbano.pdf

14:40 Astroparticles / Cosmology connections

Speaker: Licia Verde

Slides Verde.pdf

15:20 Towards BSM model building from asymptotic safety

Speaker: Astrid Eichhorn

Slides Eichhorn.pdf

16:00 → 16:30 Coffee break

16:30 → 17:50 Plenary Session

Convener: Christophe Grojean

16:30 Dark matter: beyond the vanilla case

Speaker: Kai Schmidt-Hoberg

Slides Schmidt-Hoberg.pdf

17:10 News from $\nu$'s: Hot Topics in Neutrino Physics

Speaker: Joachim Kopp

Slides Kopp.pdf

18:30 → 21:30 Welcome reception

Wednesday, 26 September

09:00 → 11:00 Plenary Session

Convener: Anna Kulesza

09:00 Precision measurements (ATLAS/CMS)

Speaker: Ulrike Blumenschein

Slides Blumenschein.pdf

09:40 Multiparticle production and automation

Speaker: Ansgar Denner

Slides Denner.pdf

Video recording https://webcast.desy.de/?p=8048

10:20 Top quark physics with high precision

Speaker: Michal Czakon

Slides Czakon.pdf

Video recording https://webcast.desy.de/?p=8050

11:00 → 11:40 Coffee break

11:40 → 13:00 Plenary Session

Convener: Gudrun Heinrich

11:40 Exploring the top-Higgs connection at colliders

Speaker: Fabio Maltoni

Slides Maltoni.pdf

Video recording https://webcast.desy.de/?p=8060

12:20 Higgs physics for the HL-LHC and beyond

Speaker: Michael Spannowsky

Slides Spannowsky.pdf

13:00 → 14:00 Lunch

14:00 → 16:00 Parallel Session: Cosmo 1: DM (axions & astrophysics)

14:00 Dark Decay of the Neutron

There is a long-standing discrepancy between the neutron lifetime measured from trapped neutrons versus those decaying in flight. In this talk, I will give an brief description of the experimental status of this puzzle and describe recent proposals to explain it by allowing the neutron to decay into hidden sector particles. In particular, I will focus on a scenario in which the neutron decays into 2 invisible particles: a dark Dirac fermion and an unstable dark photon. This setup can be consistent with all constraints if the fermion is a subdominant component of the dark matter. I will discuss the limits on the model’s parameter space that are derived from the existence of two solar mass neutron stars, direct and indirect dark matter detection, supernova observations, and cosmological considerations.

Speaker: Jonathan Cornell (University of Cincinnati)

Slides Cornell_Dark_Neutron_DESY_2018.pdf

14:20 Tricking Non-Poissonian Template Fitting: Dark Matter Hiding at the Galactic Center?

The Galactic Center GeV excess is firmly detected. While there is statistical evidence suggesting the excess originates largely from point sources, its interpretation as a signal of annihilating dark matter has not been conclusively ruled out. We examine the degree to which assumptions about the diffuse modeling and source populations could affect non-Poissonian template fitting methods that indicate a point-source origin for the excess. We find a proof-of principle example where a simulated dark matter signal can instead be attributed to point sources by the NPTF, in a simulation including unmodeled sources in the Fermi Bubbles. We confirm this effect is possible in the real Fermi data, finding that an injected dark matter signal is misattributed to point sources.

Speaker: Dr Rebecca Leane (MIT)

Slides RKLeane_DESY18.pdf

14:40 On Dark Matter Accretion in Neutron Stars

If Dark Matter (DM) interacts with nucleons and/or electrons it can be trapped in celestial bodies. For a Neutron Star (NS), DM accumulating in the center could form a core which could further gravitationally collapse into a black hole. The requirement that such collapses do not occur gives constraints on the DM mass and interactions. Such phenomena crucially depends on the amount of DM that can accumulate in NS. In this talk, we re-evaluate in detail the maximum amount of DM that could be accumulated in NS by carefully considering the fact that neutrons form a highly degenerate fermi plasma. We find that for asymmetric bosonic DM, for masses below 1 GeV constraints are significantly smaller than previously obtained in the literature.

Speaker: Dr Raghuveer Garani (Universite Libre De Bruxelles)

Slides desy2018.pdf

15:00 Global Fits of Axion Models

One of the two possible scenarios for the Peccei-Quinn symmetry is to break before the end of inflation without being restored afterwards. In this case, the axion field is homogeneous across the observable universe and its initial field value is random. A Bayesian analysis of this scenario can quantify the well-known existence of “natural” values for the initial misalignment angle and axion mass. This is particularly interesting when embedded into a consistent, global statistical analysis, including most of the known experimental constraints. We achieve this using the global fitting software GAMBIT. Finally, the predictivity of such a global fit can be improved if cooling anomalies are included.

Speaker: Mr Sebastian Hoof (Imperial College London)

Slides 2018_desy_hoof.pdf

15:15 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 of density fluctuations when vacuum re-alignment 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 under the arXiv number 1708.04466.

Speaker: Andreas Pargner (Karlsruhe Insitute of Technology)

Slides 18_DESY_theory_minicluster_slides.pdf

15:30 A Proposal to Detect Dark Matter Using Topological Insulators

Antiferromagnetically doped topological insulators (A-TI) are among the candidates to host dynamical axion fields and axion-polaritons; weakly interacting quasiparticles that are analogous to the dark axion, a long sought after candidate dark matter particle. Here we demonstrate that using the axion quasiparticle and antiferromagnetic fluctuations in A-TI's in conjunction with low-noise methods of detecting THz photons presents a viable route to detect axion dark matter with mass 0.7 to 3.5 meV, a range currently inaccessible to other dark matter detection experiments and proposals.

Speaker: Dr David Marsh (University of Goettingen)

Slides mev_axion_detection_marsh.pdf

15:50 Polarized direct detection of dark matter

Speaker: Kare Fridell

14:00 → 16:00 Parallel Session: Cosmo 2: Inflation & Early Universe

14:00 Primordial black holes from single-field inflation

I will discuss the formation of primordial black holes from single-field inflation. If time permits, I will also explain why the two-point statistics of primordial black holes is important to estimate their present merger rate

Speaker: Guillermo Ballesteros (IFT UAM-CSIC)

14:20 Gauge Field and Fermion Production during Axion Inflation

A Chern-Simons coupling with a gauge field is common in axion inflation. It is well known that this coupling leads to interesting phenomenology via the resonant production of helical gauge fields; e.g., gravitational wave, magnetogenesis, leptogenesis, etc. In this talk, we extend the previous analysis to the case where chiral fermions are charged under this gauge field which couples with the inflaton via the Chern-Simons coupling. This is the case for instance with the SM gauge group. We discuss how this coupling modifies the phenomenology by the associated production of these chiral fermions.

Speaker: Dr Kyohei Mukaida (DESY)

Slides kmukaida.pdf

14:40 Relaxion Dark Matter

I discuss a scenario in which the relaxion field, whose evolution in the early universe is responsible for the smallness of EW scale compared to the cutoff of the theory, also constitutes the Dark Matter of the Universe.

Speaker: Enrico Morgante (DESY)

Slides Morgante-RelaxionDM.pdf

15:00 Gravitational Waves from Sub-MeV Cosmolocial Phase Transitions

The next generation of gravitational-wave (GW) observatories will cover a vast array of frequencies, enabling us to probe astronomical and cosmological phenomena in a way complementary to current and future collider experiments. One such phenomenon is a cosmological first-order phase transition (PT) driven by the temperature dependence of the effective potential in the expanding and cooling universe. The transition proceeds by the nucleation of bubbles, which expand and finally collide, thereby sourcing gravitational radiation. In our work we focus on the detection capabilities of pulsar timing arrays (PTAs), which are sensitive to PTs around the keV to MeV scale. Light relics in this mass range can easily come in conflict with cosmological bounds, which I will also discuss. I will further present two toy models featuring first-order transitions, induced at tree-level and at one-loop level respectively.

Speaker: Mr Moritz Breitbach (Johannes Gutenberg University Mainz)

Slides Breitbach_DESY2018.pdf

15:15 Consistent early and late time cosmology from the RG flow of gravity

The compatibility of cosmological constraints on inflation and the cosmological constant with the asymptotic safety scenario of quantum gravity is discussed. The effective action is taken to be of $f(R)$ form, truncated to second order. The flow generated by the Functional Renormalisation Group Equation is analysed and it is found to allow for trajectories that are compatible with the observational constraints on the parameters of the action, both at early and late cosmological times. In particular, the gravitational effective dynamics generated in the trans-Planckian regime flows to Starobinsky inflation at early times and to standard Einstein Gravity with a cosmological constant at late times. Moreover, the cosmological constant acquires an energy dependence at $10^{−2}$ eV, increasing from its current value of $10^{−66}$ eV$^2$ on Hubble scale to a value of $10^{30}$ eV$^2$ at inflation scale.

Speaker: Mr Chris Ripken (Radboud University, Nijmegen)

15:30 Primordial Gravitational Waves and the Swampland

The swampland conjectures seek to distinguish effective field theories which can be consistently embedded in a theory of quantum gravity from those which can not (and are hence referred to as being in the swampland). We consider two such conjectures, known as the Swampland Distance and de Sitter Conjectures, showing that taken together they place bounds on the amplitude of primordial gravitational waves generated during single field slow-roll inflation. The bounds depend on two parameters which for reasonable estimates restrict the tensor-to-scalar ratio to be within reach of future surveys.

Speaker: Dr Ander Retolaza (DESY)

Slides retolaza.pdf

15:50 Cosmological aspects of Multifield NMSSM-inspired Higgs Inflation

Speaker: Michael Matlis

14:00 → 16:00 Parallel Session: Pheno 1: BSM I

14:05 Heavy Neutrinos and Safe Jet Vetoes in Hadron Collisions

Heavy neutrinos $(N)$ are a common prediction in low-scale neutrino mass models and may be accessible at experiments such as LHC, or its potential successors like the 27 TeV HE-LHC or 100 TeV VLHC. We show how collider searches for such objects employing an usual jet veto scheme can radically improve signal and background separation, and hence greatly improve sensitivity to EW- and TeV-scale heavy $N$. QCD properties of this veto scheme and anticipated sensitivities at future facilities are also presented.

Speaker: Richard Ruiz (Durham University)

Slides rruiz_HeavyNVeto_DESY_TH_2019.pdf

14:25 Walking Technicolor in light of Z' searches at the LHC

In the post-Higgs era of particle physics there remain many open questions requiring physics Beyond the Standard Model. Minimal Walking Technicolor (WTC) theory provides an alternative to the SM Higgs mechanism of mass generation, where a new strong force with 'walking' (slowly running) coupling breaks electroweak symmetry dynamically. This resolves the hierarchy problem as well as providing a composite Higgs boson that is consistent with observation. The phenomenology of WTC includes two triplets of heavy vector bosons (Z',Z''). We interpret the limits from Run 2 LHC data on neutral Drell-Yan processes in the WTC parameter space, where the Z' and Z'' provide complementary exclusions on WTC. We also evaluate the potential of the LHC to probe the WTC parameter space at future upgraded energy and higher luminosities.

Speaker: Azaria Coupe (University of Southampton)

Slides DESY_particle_physics_challenges.pdf

14:42 Exploring CPT violation in B-Bbar oscillation.

CPT is presumed to be one of the fundamental symmetry of nature. Lorentz invariance of the quantum field theories and CPT symmetry are intertwined with each other. With the advent of high precision experimental era, we should test these fundamental symmetries whose violations can have profound impact on our understanding of the physical laws. In this talk, I will talk about observing CPT violations of a non-dynamical origin in $B^0-\bar{B}^0$ mixing.

Speaker: Abinash Kumar Nayak (IMSc, HBNI, Chennai)

Slides CPT-DESY.pdf

14:59 Five-particle contributions to the inclusive rare $\bar B \to X_{s(d)}\ell^+\ell^-$ decays

We calculate tree-level contributions to the inclusive rare $\bar B \to X_{s(d)} \, \ell^+\ell^-$ decays. At the partonic level they stem from the five-particle process $b \to s(d) \, q \bar q \, \ell^+\ell^-$, with $q \in \{u,d,s\}$. While for $b \to d$ transitions such five-body final states contribute at the same order in the Wolfenstein expansion compared to the three-body partonic decay, they are CKM suppressed in $b \to s$ decays. In the perturbative expansion, we include all leading-order contributions, as well as partial next-to-leading order QCD and QED effects. In the case of the differential branching ratio, we present all results completely analytically in terms of polylogarithmic functions of at most weight three. We also consider the differential forward-backward asymmetry, where all except one interference could be obtained analytically. From a phenomenological point of view the newly calculated contributions are at the percent level or below. A phenomenological update on $\bar B \to X_{s(d)}\ell^+\ell^-$ results will also be presented.

Speaker: Qin Qin (University of Siegen)

Slides Qin-DESY.pdf

15:19 Hunting All the Hidden Photons - and more?

I want to shed some light on the full constraining power of experimental bounds derived for hidden photons by applying them to gauge bosons of a weakly coupled $U(1)_{B-L}$, $U(1)_{L_\mu-L_e}$, $U(1)_{L_e-L_\tau}$ and $U(1)_{L_\mu-L_\tau}$. In contrast to a hidden photon that acquires universal couplings to charged SM particles through kinetic mixing with the photon, several SM particles are uncharged under these gauge groups. Also taking into account loop-induced kinetic mixing the hidden photon bounds are drastically altered for the different gauge groups. As the associated gauge bosons of these anomaly-free groups are well-motivated mediators to a dark sector I further want to discuss some interesting dark matter phenomenology of a light thermal relic charged under the new symmetry.

Speaker: Patrick Foldenauer (Institut für Theoretische Physik, Heidelberg University)

Slides HP+DM_PF_short.pdf

15:36 B+L violation at colliders and new physics

Chiral electroweak anomalies predict baryon (B) and lepton (L) violating fermion interactions, which can be dressed with large numbers of Higgs and gauge bosons. The estimation of the total B + L-violating rate from an initial two-particle state — potentially observable at colliders — has been the subject of an intense discussion, mainly centered on the resummation of boson emission, which is believed to contribute to the cross-section with an exponential function of the energy, yet with an exponent (the “holy-grail” function) which is not fully known in the energy range of interest. In this article we focus instead on the effect of fermions beyond the Standard-Model (SM) in the polynomial contributions to the rate. It is shown that B + L processes involving the new fermions have a polynomial contribution that can be several orders of magnitude greater than in the SM, for high centre-of-mass energies and light enough masses. We also present calculations that hint at a simple dependence of the holy grail function on the heavy fermion masses. Thus, if anomalous B + L violating interactions are ever detected at high-energy colliders, they could be associated with new physics.

Speaker: Carlos Tamarit (Technische Universität München)

Slides BL.pdf

14:00 → 16:00 Parallel Session: String 1

14:00 Scattering Amplitudes from Geometry at Infinity

Speaker: Song He

Slides 1_Song_He.pdf

14:30 Elliptic polylogarithms for the next generation of Feynman integrals

Speaker: Johannes Brödel

Slides 2_Johannes_broedel.pdf

15:00 Conformal Symmetry and Feynman Integrals

Speaker: Simone Zoia

Slides 3_Simone_Zoia.pdf

15:20 Analytical properties of scattering amplitudes from multiple polylogarithms

Speaker: Vsevolod Chestnov

Slides 4_Seva_Chestnov.pdf

15:35 New relations for graviton-matter amplitudes

Speaker: Wadim Wormsbecher

Slides 5_Wadim_Wormsbecher.pdf

16:00 → 16:30 Coffee break

16:30 → 19:00 Parallel Session: Cosmo 3: DM (particle physics)

16:30 Higgs enhancement and bound state formation in coannhilation scenarios

Given the growing constraints on WIMP dark matter, coannihilation scenarios are gaining more and more interest. However, in order to theoretically predict the relic density with a certain precision for a specific model, different effects have to be taken into account. We introduce a so far neglected effect - Higgs enhancement - that significantly alters the prediction of the dark matter abundance. While the importance of long-range interactions mediated by vector bosons is well established, the Higgs is usually thought to transmit contact interactions only. We show however that the Higgs can lead to similarly striking effects. Furthermore, we will demonstrate the significant impact of bound state formation via emission of a gauge boson in coannihilation scenarios featuring non-Abelian long-range interactions. While its impact was previously disregarded in the literature, we will show examples in which the dark matter density prediction would be off by up to 240% when neglecting radiative formation and decay of particle-antiparticle bound states.

Speaker: Dr Julia Harz (LPTHE / ILP Paris)

Slides DESYTheoryWorkshop2018.pdf

16:50 VERY supersymmetric dark sectors

If supersymmetry exists at any scale, it may be a preserved symmetry in the dark sector enforcing a degeneracy between its lowest lying fermions and bosons. In this talk I explore the plausibility of this scenario, the implications for the early universe, and the corresponding signatures. As I will show this completely changes the thermal history of the dark sector resulting in the sector to undergo "codecay" in the bulk of the parameter space. This results in new phenomenological signatures and presents a new way to discover (potentially high scale) supersymmetry.

Speaker: Mr Jeff Dror (Lawrence Berkeley National Laboratory)

Slides WorkshopTalk_v2.pdf

17:10 Dynamic Freeze-In: Impact of Thermal Masses and Cosmological Phase Transitions on Dark Matter Production

The cosmological abundance of dark matter can be significantly influenced by the temperature dependence of particle masses and vacuum expectation values. In the paper we illustrate this point in three simple freeze-in models. The first one, which we call kinematically induced freeze-in, is based on the observation that the effective mass of a scalar temporarily becomes very small as the scalar potential undergoes a second order phase transition. This opens dark matter production channels that are otherwise forbidden. The second model we consider, dubbed vev-induced freeze-in, is a fermionic Higgs portal scenario. Its scalar sector is augmented compared to the Standard Model by an additional scalar singlet, S, which couples to dark matter and temporarily acquires a vacuum expectation value (a two-step phase transition or “vev flip-flop”). While $\langle S\rangle \neq 0$, the modified coupling structure in the scalar sector implies that dark matter production is significantly enhanced compared to the $\langle S\rangle = 0$ phases realised at very early times and again today. The third model, which we call mixing-induced freeze-in, is similar in spirit, but here it is the mixing of dark sector fermions, induced by non-zero hSi, that temporarily boosts the dark matter production rate. For all three scenarios, we carefully dissect the evolution of the dark sector in the early Universe. We compute the DM relic abundance as a function of the model parameters, emphasising the importance of thermal corrections and the proper treatment of phase transitions in the calculation.

Speaker: Mr Lukas Mittnacht (Johannes-Gutenberg University)

Slides LMittnachtDynamicFreezeIn.pdf

17:25 BBN constraints on MeV-scale dark sectors

We study constraints from Big Bang Nucleosynthesis on inert particles in a dark sector which contribute to the Hubble rate and therefore change the predictions of the primordial nuclear abundances. We pay special attention to the case of MeV-scale particles decaying into dark radiation, which are neither fully relativistic nor non-relativistic during all temperatures relevant to Big Bang Nucleosynthesis. As an application we discuss the implications of our general results for models of self-interacting dark matter with light mediators.

Speaker: Mr Marco Hufnagel (DESY Hamburg)

Slides DTW_2018_Marco_Hufnagel.pdf

17:40 Consequences of a XENONnT/LZ signal for the LHC and thermal dark matter production

The discovery of dark matter (DM) at XENONnT or LZ would place constraints on DM particle mass and coupling constants. It is interesting to ask when these constraints can be compatible with thermal production of DM. We address this question within the most general set of renormalizable models that preserve Lorentz and gauge symmetry, and that extend the standard model by one DM candidate of mass $m_{DM}$ and one particle of mass $M_{med}$ mediating DM-quark interactions. We find that for most of the models considered here, O(100) signal events at XENONnT/LZ and the DM thermal production are only compatible for resonant DM annihilations. Furthermore, we develop a method to forecast the outcome of the LHC Run 3 based on the same hypothetical detection of O(100) signal events at XENONnT. Applying our analysis to simulated data, we find that at the end of the LHC Run 3 only two mutually exclusive scenarios would be compatible with the detection of O(100) signal events at XENONnT, depending on the detection or lack of detection of a monojet signal. This would significantly narrow the range of possible dark matter–nucleon interactions. Finally, we want to present an outlook on how this analysis can be extended to inlcude dijet-searches for the mediator particle at the LHC.

Speaker: Martin B. Krauss (Chalmers University of Technology)

Slides presentation_krauss.pdf

18:00 Is self-interacting dark matter with no light mediator viable?

Self-interacting dark matter is a well-motivated solution to the core-vs-cusp and the too-big-to-fail problems of the ΛCDM model. In this scenario, a light particle mediating the self-interactions is typically invoked in order to achieve velocity-dependent effects. In this talk, I will argue that a light mediator is not the only possible way to do that. In particular, I will discuss two new ideas: dark matter scenarios with self-heating as well as dark matter resonant scattering.

Speaker: Dr Camilo Alfredo Garcia Cely (DESY)

Slides TalkGarciaCely.pdf

18:20 Self-interacting dark matter with a stable vector mediator

Light vector mediators can naturally induce velocity-dependent dark matter self-interactions while at the same time allowing for the correct dark matter relic abundance via thermal freeze-out. If these mediators subsequently decay into Standard Model states such as electrons or photons however, this is robustly excluded by constraints from the Cosmic Microwave Background. We study to what extent this conclusion can be circumvented if the vector mediator is stable and hence contributes to the dark matter density while annihilating into lighter degrees of freedom. We find viable parts of parameter space which lead to the desired self-interaction cross section of dark matter to address the small-scale problems of the collisionless cold dark matter paradigm while being compatible with bounds from the Cosmic Microwave Background and Big Bang Nucleosynthesis observations.

Speaker: Dr Sebastian Wild (DESY)

Slides Talk_SebastianWild.pdf

18:40 Cooling self-interacting dark matter halos

Dark sector models with light or massless mediators naturally introduce elastic and inelastic self-interactions of dark matter. The heat exchange induced by the elastic scattering permits the gravothermal evolution of the halo. Through the evolution, a halo with a cuspy density profile develops a core first but ultimately collapses to a cuspy density profile. We find that a mild inelastic scattering can significantly accelerate this evolution process. Constraints on the inelastic scattering cross section and the dissipated energy per collision can be inferred from the density cores of dwarf galaxies with low baryonic contents.

Speaker: Yiming Zhong (Boston University)

Slides Yiming_Zhong_DESY.pdf

16:30 → 19:00 Parallel Session: Pheno 2: Higgs physics + SUSY

16:30 NLO Higgs boson pair production in the ElectroWeak Chiral Lagrangian framework

We will discuss Higgs Boson pair production at full NLO including deviations from the Standard Model arising in an Effective Field Theory framework, the Electro-weak chiral Lagrangian (EWChL). We will briefly review the calculation and then show results for some benchmark points in the BSM parameter space. Subsequently we will discuss how to write the cross section as a function of the 5 anomalous couplings arising in the Higgs sector. We will show iso-countours and 3-D plots based on this parametrization, which illustrate the behaviour of the total and differential cross sections in terms of the anomalous couplings.

Speaker: Mr Matteo Capozi (MPI)

Slides Capozi_Particle_Physics_Challenges.pdf

16:47 Role of the Z polarization in the pp > ZH, H > bb measurement.

In this talk I show that the Z boson polarization has relevant information to distinguish the signal $pp\to ZH$, $H\to b\bar{b}$ from the dominant irreducible background $Zb\bar{b}$, and can help us to observe the largest Higgs boson branching ratio in this channel.

Speaker: Junya Nakamura (Universität Tübingen)

Slides nakamura.pdf

17:07 Electroweak Phase Transition in the N2HDM

The generation of the observed matter-antimatter asymmetry in the universe through baryogenesis cannot be explained in the Standard Model. We therefore investigate the possibility of a strong first order electroweak phase transition in the Next-to-Two-Higgs Doublet model (N2HDM) where we extended the CP-conserving Two-Higgs-Doublet model with an additional real singlet. The type I and II of the N2HDM are considered where one of the three neutral CP-even Higgs bosons can be the SM-like Higgs boson. After imposing theoretical and experimental constraints, the requirement of the strong phase transition leads to testable implications for the searches at the LHC. We find preferred mass configurations for the non SM-like Higgs bosons and show the implications on the signal rates of the SM-like Higgs boson decay channels. We also use our results to investigate the interplay between a strong phase transition and the size of the trilinear Higgs self-couplings.

Speaker: Mr Jonas Mueller (ITP-KIT)

Slides Talk_JonasM.pdf

17:24 Mixed QCD-electroweak corrections to Higgs gluon fusion

The study of the Higgs boson properties is one of the main tasks of contemporary high-energy physics. Among Higgs properties, its interaction with gluons is interesting since it can be facilitated by yet unknown elementary particles. One of the major sources of uncertainty in the theoretical description of $ggH$ coupling originates from mixed QCD-electroweak contributions. The NLO QCD corrections to these contributions were evaluated in the approximation where electroweak boson masses were considered to be significantly larger than the mass of the Higgs boson and it is desirable to compute these corrections for physical masses of the gauge bosons and the Higgs boson. I will present a major step towards this goal and describe first the analytic evaluation of NLO mixed QCD-EW three-loop virtual corrections to $gg \to H$, and then their implementation in the evaluation of the total cross section for $gg \to H$ in the soft-gluon approximation for real corrections.

Speaker: Mr Marco Bonetti (TTP KIT)

Slides BONETTI_DESY.pdf

17:41 Higgs Inflation and the NMSSM

In the context of canonical superconformal supergravity, Higgs inflation can be elegantly incorporated with a non-minimal Higgs coupling to supergravity. Such a conformal candidate model can be the Next-to-Minimal Supersymmetric Standard Model. Superconformal breaking induces extra terms in the effective Superpotential at low scales. We study the phenomenology of this model at the electroweak scale and show how the Higgs spectrum differs from the model with minimal coupling and how the branching fractions of the Standard Model-like Higgs boson can be affected by the non-minimal coupling to supergravity.

Speaker: Dr Wolfgang Gregor Hollik (DESY)

Slides NMSSMinflation.pdf

18:01 The prediction of the W boson mass in an R-symmetric SUSY model

SUSY continues to elude direct searches at Run 2 of the LHC. Hence, indirect probes like electroweak precision observables are relevant to explore the parameter space of a model. The mass of W boson is such an observable where the LHC experiments are on their way improve on the uncertainties of the experimental result. The prediction for $M_W$ has been studied in depth in the MSSM and NMSSM. Here, we show the implementation of an on-shell calculation for $M_W$ in the Minimal R-symmetric Supersymmetric SM (MRSSM) extending previous work. This also includes a comparison of the use of different renormalisation schemes and their respective uncertainties when applying them to the calculation of $M_W$ in a BSM model.

Speaker: Mr Philip Dießner (DESY)

Slides PDiessner.pdf

18:21 Toward a reconstruction of the lightest squark flavour structure

We investigated different methods for the reconstruction of the lightest up-type squark flavour structure in the framework of the MSSM with non minimal flavour violation.

Speaker: Mr Jordan BERNIGAUD (LAPTh)

18:38 The fate of the Littlest Higgs Model with T-parity under 13 TeV LHC Data

We scrutinize the allowed parameter space of Little Higgs models with the concrete symmetry of T-parity by providing comprehensive LHC analyses of all relevant production channels of heavy vectors, top partners, heavy quarks and heavy leptons and all phenomenologically relevant decay channels. Constraints on the model will be derived from the signatures of jets and missing energy or leptons and missing energy by using the collider phenomenology tool CheckMATE which exploits all available LHC BSM searches at center-of-mass energies of 8 and 13 TeV. Besides the symmetric case, we also study the case of T-parity violation.

Speaker: Dr Daniel Dercks (University of Hamburg)

Slides Dercks_DESY.pdf

16:30 → 19:00 Parallel Session: Pheno 3: QCD and precision tests

16:30 Analytic Resummation for multi-differential cross sections at the LHC

We present work on analytically resummed predictions for two classes of multi-differential observables at the LHC, namely (1) the simultaneous measurement of the transverse momentum of a Drell-Yan pair with event shapes like beam thrust and (2) 0-jet cross sections with realistic jet selection criteria that are relaxed beyond a certain jet rapidity cut. Common to both observables is their intricate all-order structure in the soft-collinear limit. This structure is reflected in the multi-scale extensions of Soft-Collinear Effective Theory (SCET) which we employ to achieve their resummation. Generic features that arise in both calculations include the presence of multi-differential soft and collinear matrix elements and their refactorization in kinematic limits. These features make the resummation more challenging than the single-differential case or the well-known joint resummation with threshold effects (where the threshold limit simplifies the calculation). We also discuss technical challenges such as ensuring that integrals of the double spectrum recover the resummed single-differential result. We will close by presenting resummed predictions for the double-differential Drell-Yan spectrum at NNLL and for 0-jet cross sections with a jet rapidity cut at NLL$'$.

Speaker: Mr Johannes Michel (DESY)

Slides Michel_DESY_T_Workshop.pdf

16:45 Soft factorization in multi-parton scattering

Multi-parton interactions in proton-proton scattering are processes in which two or more pairs of partons undergo a hard interaction. In order to rigorously describe multi-parton scattering in perturbative QCD, one needs to prove a factorization theorem that allows one to separate the hard interactions from the collinear and soft ones, in a similar way as has already been done for single-parton scattering. We introduce the strategy applied in the proof of the decoupling of soft gluons from the collinear sub-processes, which is based on a recursive application of Ward identities, and give a sketch of the procedure leading to the final formula.

Speaker: Mr Riccardo Nagar (DESY)

Slides nagar_soft_factorization.pdf

17:00 Next to Leading Power Corrections: Resummation and Improving Fixed Order Subtractions

In this talk I will present some recent developments in the computation of LHC observables at next to leading power in SCET. I will explain why the analytical computation of power corrections are important for fixed order calculations via subtraction methods and show the first all order resummation of logarithms at subleading power for an event shape.

Speaker: Mr Gherardo Vita (MIT)

Slides Vita_DESY_2018.pdf

17:18 s-channel Single Top Quark Production and Decay at NNLO in QCD

We report on a fully differential next-to-next-to-leading order (NNLO) calculation of s-channel single top (anti-)quark production with a semi-leptonic decay at the LHC, neglecting the color correlation between the light and heavy quark lines and in the narrow width approximation. The NNLO corrections can increase the cross section by about 10% in the low transverse momentum region of the top quark and reduce scale variation uncertainty. In order to compare with experimental results without unfolding procedures, we also present theoretical predictions with fiducial cuts, including total cross sections and distributions of observables used in the experimental multivariate analysis. The NNLO corrections are found to be about -8% for fiducial cross sections.

Speaker: Dr Ze Long Liu (Johannes Gutenberg University Mainz)

Slides s-top_Liu.pdf

17:36 Associated production of a top quark pair with a W or Z boson at the LHC at NNLL+NLO

The measurements of associated production of a vector boson with a top-antitop quark pair provide an important test for the Standard Model at the LHC. These are not only key processes to measure the top quark properties but also are very relevant in searches for new physics, both as being directly sensitive to it and as providing an important background. While NNLO calculations for this particular type of 2 to 3 processes are currently out of reach, a class of corrections beyond NLO can be taken into account with the help of resummation methods. In this talk we consider an application of soft gluon resummation in Mellin space to these processes at hadron colliders and discuss numerical predictions at NNLL matched to NLO precision for the LHC.

Speaker: Mr Daniel Schwartländer (Institut für theoretische Physik, Universität Münster)

Slides Talk.pdf

17:51 Precise tests of the Standard Model with QED bound states.

Measurements of lepton magnetic moments provide important tests of the Standard Model and may lead to an indirect discovery of new physics. In my talk, I will discuss bound electron g-factor and recent progress in the computation of the higher order corrections to the magnetic moment of an electron in hydrogen-like ions. I demonstrate a modern effective field theory approach to bound state QED and show how the state-of-the-art experiments, combined with precise theoretical predictions, lead to the most accurate determination of the fundamental constants. I will present prospects for future improvements and discuss the connection with the free electron and muon anomaly.

Speaker: Dr Robert Szafron (Technical University of Munich)

Slides DESY.pdf

18:09 Resummed PT spectrum for Drell-Yan including massive bottom quark effect

We study the resummed transverse momentum spectrum for Drell-Yan production including the bottom mass effect. The pt-distribution of DY or Z boson is very important observable at the LHC, particularly to the ratio of W boson and Z boson spectrum to precisely measure of the W boson mass. The presence of an extra mass scale namely the bottom mass along with the Hard scale and the pt-scale makes it very difficult to study within QCD. The three different mass scales give rise to several mass hierarchies leading to large logarithms which needs to be resummed at all orders to get a meaningful result. Moreover the different regions have to be properly matched to get a smooth distribution avoiding double counting or gaps. For these kind of problem, effective theories show a better grasp onto the problem. Using SCET based factorisation we resum these large logarithms in a systematic way upto NNLLp accuray. We discuss different theoretical issues namely order counting, rapidity divergences etc. We identify two different kind of contributions namely the primary effect where bottom quark initiates the hard process and the secondary effect where bottom quark contributes through loop. Both these contributions are included into our calculation. Finally we present properly matched pt-distribution which will be useful at the LHC to the measurement of Z boson and W boson properties.

Speaker: Dr Goutam Das (DESY)

Slides desytheory18.pdf

18:27 Quasi Transverse Momentum Dependent PDFs from Lattice QCD

Transverse-momentum dependent PDFs (TMDPDFs) are an important ingredient for high-precision measurements of transverse momentum distributions, e.g. of the Higgs boson, and an interesting probe of the proton structure itself. So far, they have only been poorly extracted from measurement. Recently, much progress has been made in calculating PDFs from lattice QCD using the so-called quasi PDF approach. I will briefly review quasi PDFs and discuss the construction of quasi TMDPDFs and to what extent they can be used to directly calculate TMDPDFs with Lattice QCD. In particular, complications arising from combining soft and collinear matrix elements are pointed out and possible solutions are suggested.

Speaker: Markus Ebert (MIT)

Slides Ebert_DESY2018.pdf

18:45 Resummation at next-to-leading power

In the last few years, the resummation of large logarithmic contributions up to next-to-next-to-next-to-leading logarithm has been performed for a number of observables within Soft Collinear Effective Theory (SCET). This formalism has been successful at improving theoretical predictions for several important observables in collider physics. One of the first examples is threshold resummation in Drell-Yan production and more recently N-jettiness. In this talk, the framework for threshold resummation in Drell-Yan production at subleading power within the position space SCET formalism will be demonstrated. I will present the general factorisation formula and explain the contributing ingredients focusing on the power suppressed effects and new features which enter the factorisation at next-to-leading power. I will also discuss the resummation of power suppressed logarithms.

Speaker: Mr Sebastian Jaskiewicz (Technische Universität München)

Slides SJ_DESY_talk.pdf

16:30 → 19:00 Parallel Session: String 2

16:30 Mellin Amplitudes for Fermionic Correlators

Speaker: Josua Faller

Slides 1_Josua_Faller.pdf

16:50 Interactions of arbitrary spin gauge fields and special dimensions

Speaker: Karapet Mkrtchyan

Slides 2_Karapet_Mkrtchyan.pdf

17:10 Intersecting branes, Higgs sector, and chirality from N = 4 SYM with soft SUSY breaking

Speaker: Harold Steinacker

Slides 3_Harold_Steinacker.pdf

17:40 Twist fields and moduli space of D-branes

Speaker: Luca Mattiello

Slides 4_Luca_Mattiello.pdf

18:00 Global tensor-matter transitions in F-theory

Speaker: Markus Dierigl

Slides 5_Markus_Dierigl.pdf

18:20 Strongly deformed N=4 SYM in the double scaling limit as an integrable CFT

Speaker: Michelangelo Preti

Slides 6_Michelangelo_Preti.pdf

18:40 Integrability in N = 1 gauge theories

Speaker: Jan-Peter Carstensen

Slides 7_Jan-Peter_Carstensen.pdf

Thursday, 27 September

09:00 → 11:00 Plenary Session

Convener: Gudrid Moorgat-Pick

09:00 Direct searches for new physics at the LHC (ATLAS/CMS)

Speaker: Filip Moortgat

Slides Moortgat.pdf

09:40 New solutions to hierarchy problems

Speaker: Nathaniel Craig

Slides Craig.pdf

Video recording https://webcast.desy.de/?p=7848

10:20 The $\sigma_8$ and $H_0$ problems and BSM of Cosmology

Speaker: Martin Schmaltz

Slides Schmaltz.pdf

Video recording https://webcast.desy.de/?p=8065

11:00 → 11:40 Coffee break

11:40 → 13:00 Plenary Session

Convener: Frank Tackmann

11:40 QCD at high precision for the LHC

Speaker: Lorenzo Tancredi

Slides Tancredi.pdf

Video recording https://webcast.desy.de/?p=8068

12:20 Jet substructure and machine learning

Speaker: Ian Moult

Slides Moult.pdf

Video recording https://webcast.desy.de/?p=8070

13:00 → 14:00 Lunch

14:00 → 15:45 Parallel Session: Cosmo 4: PBH and GW

14:00 Gravitational wave cosmology with LISA

In this talk I will present the current status of cosmological forecasts for the Laser Interferometric Space Antenna (LISA). I will show that LISA will constitute a unique cosmological probe able to measure the expansion of the universe from low redshifts (z=0.01) up to very large redshifts (z=10). This is made possible by the use of different gravitational wave sources as standard sirens: stellar origin black hole binaries (low redshift), extreme mass ratio inspirals (intermediate redshift) and massive black hole binaries (high redshift). I will discuss the methodologies used to obtain cosmological constraints and present the latest cosmological forecasts based on state of the art simulated catalogues of gravitational wave sources.

Speaker: Dr Nicola Tamanini (Max Planck Institute for Gravitational Physics (AEI))

Slides Talk.pdf

14:20 Cuckoo's Eggs in Neutron Stars: Can LIGO Hear Chirps from the Dark Sector?

We explore in detail the possibility that gravitational wave signals from binary inspirals are affected by a new force that couples only to dark matter particles. We discuss the impact of both the new force acting between the binary partners as well as radiation of the force carrier. We identify numerous constraints on any such scenario, ultimately concluding that observable effects on the dynamics of binary inspirals due to such a force are not possible if the dark matter is accrued during ordinary stellar evolution. Constraints arise from the requirement that the astronomical body be able to collect and bind at small enough radius an adequate number of dark matter particles, from the requirement that the particles thus collected remain bound to neutron stars in the presence of another neutron star, and from the requirement that the theory allows old neutron stars to exist and retain their charge. Thus, we show that any deviation from the predictions of general relativity observed in binary inspirals must be due either to the material properties of the inspiraling objects themselves, such as a tidal deformability, to a true fifth force coupled to baryons, or to a non-standard production mechanism for the dark matter cores of neutron stars. Viable scenarios of the latter type include production of dark matter in exotic neutron decays, or the formation of compact dark matter objects in the early Universe that later seed star formation or are captured by stars.

Speaker: Dr Ranjan Laha (Johannes Gutenberg University Mainz)

Slides DESY_Theory_workshop_2018.pdf

14:40 Leptophilic dark matter from gauged lepton number: Phenomenology and gravitational wave signatures

In this work, we consider a model in which the SM is extended by a lepton number gauge group $U(1)_\ell$. The arising gauge anomalies are canceled by adding two sets of SM vector-like leptons. We further add a scalar field that spontaneously breaks $U(1)_\ell$. A residual global symmetry ensures the stability of the lightest additional lepton, thus providing a dark matter candidate. We investigate current and future constraints on the model from collider searches as well as dark matter experiments. We further study the lepton number breaking phase transition, particularly focusing on its potential to generate a stochastic gravitational wave background accessible to GW interferometry as a complementary way to probe the model.

Speaker: Mr Eric Madge (Johannes Gutenberg University Mainz)

Slides DM_from_gauged_L.pdf

14:55 Gravitational Wave Constraints on Clustered Primordial Black Hole Dark Matter

Primordial black holes (PBHs) are a well-motivated candidate for dark matter that regained research interest after the first detections of gravitational waves by LIGO. PBHs can form binaries in the early universe. Due to the production process of PBHs, e.g. by large and rare density perturbations, clustering of PBHs can become important. This is used in the literature to avoid current exclusion limits. However, we point out that once the clustering is high enough such that the merger time for typical PBH binaries is sufficiently less than the age of the universe, multiple successive mergers, i.e. merging of binaries consisting of previously merged PBHs, can occur and gain importance. This has been neglected up to now. We present a simple cascading model taking into account this effect and show that it enhances existing constraints due to the observed binary black hole merger rate, the stochastic gravitational wave background, the effective number of additional neutrino species, and the conversion of PBHs as dark matter to gravitational waves as dark radiation.

Speaker: Mr Paul Frederik Depta (DESY)

Slides PBHlimits_DTW_2018_FDepta.pdf

15:10 Gravitational waves produced by compressible MHD turbulence from cosmological phase transitions

We discuss the gravitational wave spectrum produced by magneto-hydrodynamic turbulence in a first order phase transitions. In particular, we discuss the impact of the rate of turbulent decorrelation on the spectrum of gravitational waves and how this can impact future constraints on cosmological first order phase transitions. Additionally, we discuss how "sound-wave" driven turbulence can transform into vortically driven turbulence in the presence of magnetic fields, some inital vorticity or due to a non-barotropic flow. This leads to important changes of an initially sound-wave driven gravitational wave spectrum at later times in the evolution affecting both the amplitude and the shape of the spectrum.

Speaker: Peter Niksa (Uni HH II. Institut für Theoretische Physik)

Slides Niksa_DesyTheory2018.pdf

15:25 Black Holes' Dark Dress: The impact of local Dark Matter halos on the mergers of primordial black hole binaries

The observation of gravitational waves from binary black hole mergers has renewed interest in the possibility of primordial black holes (PBHs) that are around 10 to 100 times more massive than the Sun. Such PBHs may form large numbers of binaries before matter-radiation equality and, if these binaries survive until today, they may contribute to the merger rate observable by LIGO and Virgo. However, if PBHs are a sub-dominant fraction of the Dark Matter (DM), they will be dressed in local DM halos which may disrupt the binaries through dynamical friction. I will present the results of N-body simulations and analytic estimates, studying the impact of this 'dark dress'. While the size and shape of PBH binaries is dramatically altered by local DM halos, there is a surprisingly subtle effect on the rate of mergers expected today. Limits on the merger rate observed by LIGO-Virgo may be translated into bounds on the fraction of DM in the form of PBHs. I will argue that our calculations place such bounds on a more solid footing, constraining the fraction of DM in the form of 10-300 solar mass PBHs to be around $10^{-3}$ or less. The techniques I present also pave the way for future studies of DM halos around astrophysical black holes and their impact on gravitational wave signals.

Speaker: Dr Bradley Kavanagh (GRAPPA, University of Amsterdam)

Slides KAVANAGH-DESY2018.pdf

14:00 → 15:34 Parallel Session: Pheno 4: Ions and other topics

14:00 The Heavy Metal Path to New Physics

We explore the potential to test weakly coupled New Physics in heavy ion collisions. We find that the data from heavy ion collisions at the HL-LHC can yield constraints that are only an order of magnitude weaker than those expected from proton-proton collisions for generic parameter choices in well-motivated New Physics scenarios, and that they may even achieve the same sensitivity in some corners in the parameter space.

Speaker: Jan Hajer

Slides jan_hajer.pdf

14:20 Four-jet and three-jet plus gamma DPS production in pp and pA collisions at the LHC

In spite of the recent progress in both theoretical and experimental studies many aspects of $\textit{multiple parton interactions}$ (MPI) still require a detail investigation. In particular, $\textit{double parton scattering}$ (DPS) processes can play a dominant role for some specific kinematic regions of multi-jet production, especially in $\textit{proton-nucleus}$ (pA) collisions where the total DPS cross section is approximately $\sim$3A times bigger as the corresponding total DPS cross section in $\textit{proton-proton}$ (pp) collisions. In this talk I will discuss the DPS in the four-jet and three-jet plus gamma production processes in pp and pA collisions. Specifically the impact of parton shower effects on predictions for DPS sensitive observables, the role of nuclear effects and the dependence of the DPS cross sections on different kinematical cuts and phenomenological assumptions.

Speaker: Mr Oleh Fedkevych (Institute of Theoretical Physics, Münster)

Slides DESY_Fedkevych_pp_pA.pdf

14:37 Probing of XYZ meson structure with near threshold pp and pA collisions

The spectroscopy of charmonium-like mesons with masses above the 2mD open charm threshold has been full of surprises and remains poorly understood [1]. The currently most compelling theoretical descriptions of the mysterious XYZ mesons attribute them to hybrid structure with a tightly bound cc\bar diquark [2] or cq(cq')\bar tetraquark [3 - 5] core that strongly couples to S-wave DD\bar molecular-like structures. In this picture, the production of a XYZ particle in high energy hadron collisions and its decays into light hadron plus charmonum final states proceed via the core component of the meson, while decays to pairs of open charmed mesons proceed via the DD\bar component. These ideas have been applied with some success to the X(3872) [2], where a detailed calculation finds a cc\bar core component that is only above 5% of the time with the DD\bar component (mostly D^0D^0\bar) accounting for the rest. In this picture, the X(3872) is compose of three rather disparate components: a small charmonium-like cc\bar core with r_rms < 1 fm, a larger D^+D^- component with r_rms = ħ/\sqrt(2µ+B+) ≈ 1.5 fm and a dominant component D^0D^0\bar with a huge, r_rms = ħ/\sqrt(2µ0B0)> 9 fm spatial extent. Here µ+(µ0) and B+(B0) denote the reduced mass for the D^+D^- (D^0D^0\bar) system and the relevant binding energy |mD + mD - MX(3872)| (B+ = 8.2 MeV, B0 < 0.3 MeV). The different amplitudes and spatial distributions of the D^+D^- and D^0D^0\bar components ensure that the X(3872) is not an isospin eigenstate. Instead it is mostly I = 0, but has a significant (~ 25 %) I = 1 component. In the hybrid scheme, an X(3872) is produced in high energy pA collisions via its compact (r_rms < 1 fm) charmonium-like structure and this rapidity mixes in a time (t ~ ħ/δM) into a huge and fragile, mostly D^0D^0\bar, molecular-like structure. δM is the difference between the X(3872) mass and that of the nearest cc\bar mass pole core state, which we take to be that of the χ_c1(2P) pure charmonium state which is expected to lie about 20 ~ 30 MeV above M_X(3872) [6, 7]. In this case, the mixing time, cτ_mix 5 ~ 10 fm, is much shorter than the lifetime of X(3872) which is cτ_X(3872) > 150 fm [8]. The experiments with proton-proton (pp) and proton-nuclear (pA) collisions with momentum up to 26 Gev/c and luminosity up to 10^32 cm^-2s^-1 are well suited to test this picture for the X(3872) and, possibly, other XYZ mesons. In near threshold production experiments in the √SpN ≈ 8 GeV energy range, X(3872) mesons can be produced with typical kinetic energies of a few hundred MeV (i.e. with γβ ≈ 0.3). In the case of X(3872), its decay length will be greater than 50 fm while the distance scale for the cc\bar → D^0D^0*\bar transition would be 2 ~ 3 fm. Since the survival probability of an r_rms ~ 9 fm “molecular” inside nuclear matter should be very small, X(3872) meson production on a nuclear target with r_rms ~ 5 fm or more (A ~ 60 or larger) should be strongly quenched. Thus, if the hybrid picture is correct, the atomic number dependence of X(3872) production at fixed √SpN should have a dramatically different behavior than that of the ψ', which is long lived compact charmonium state. The current experimental status of XYZ mesons together with hidden charm tetraquark candidates and present simulations what we might expect from A-dependence of X(3872) mesons in pp and pA collisions are summarized. References [1] S. Olsen, Front. Phys. 10 101401 (2015) [2] S. Takeuchi, K. Shimizu, M. Takizawa, Progr. Theor. Exp. Phys. 2015, 079203 (2015) [3] A. Esposito, A. Pilloni, A.D. Poloza, arXiv:1603.07667[hep-ph] [4] M.Y.Barabanov, A.S.Vodopyanov, S.L.Olsen, A.I.Zinchenko, Phys. Atom. Nuc. 79, 1, 126 (2016) [5] M.Yu. Barabanov, A.S. Vodopyanov, S.L. Olsen, Phys. Scripta 166 014019 (2015) [6] N. Isgur, Phys. Rev. D 32, 189 (1985) [7] K. Olive et al. (PDG), Chin. Phys. C 38, 090001 (2014) [8] The width of X(3872) is experimentally constrained to be Г X(3872) < 1.2 (90% CL) in S.-K. Choi et al (Belle Collaboration), Phys. Rev. D 84, 052004 (2011)

Speaker: Prof. Mikhail Barabanov (JINR)

14:57 The Lund Jet Plane

Lund diagrams, a representation of the phase space within jets, have long been used in discussing parton showers and resummations. We point out here that they can also serve as a powerful tool for experimentally characterising the radiation pattern within jets. We briefly comment on some of their analytical properties and highlight their scope for constraining Monte Carlo simulations. We then examine the use of the Lund plane for boosted electroweak boson tagging. When used as an input to deep-learning methods it yields high performance. Furthermore, much of that performance can be reproduced by using the Lund plane as an input to simpler log-likelihood type discriminators. This suggests a potential for unique insight and experimental validation of the features being used by machine-learning approaches. In the context of our discussion, we also highlight the importance of accounting for detector effects when considering the performance of machine-learning approaches.

Speaker: Mr Frederic Dreyer (Oxford)

Slides talk_desy18.pdf

15:17 Combining WHIZARD and Pythia 8

`WHIZARD` is a multi-purpose event generator for hadron and lepton colliders. Support for lepton beam spectra (`CIRCE1` and `CIRCE2`), polarization, initial-state radiated photons and the equivalent-photon approximation make `WHIZARD` suitable for lepton-collider physics simulations. We have added support for `Pythia 8` on an event-per-event basis, enabling the transformation from the hard process to fully showered and hadronized events while accounting for resonances and spin correlations. We compare simulated data using the new interface to results from the standard `PYTHIA6` interface and to available $\mathrm{e}^{+}\mathrm{e}^{-}$ data.

Speaker: Simon Braß (Theoretial Particle Physics - University Siegen)

Slides readme.pdf

14:00 → 15:30 Parallel Session: String 3

14:00 Inversion formula for Defects I: Defect Channel

Speaker: Pedro Liendo

Slides 1_Pedro_Liendo.pdf

14:20 Inversion formula for Defects II: Bulk Channel

Speaker: Yannick Linke

Slides 2_Yannick_Linke.pdf

14:35 4d N = 3 indices via discrete gauging

Speaker: Alessandro Pini

Slides 3_Alessandro_Pini.pdf

14:55 Deconstructing Little Strings with N = 1 Gauge Theories on Ellipsoids

Speaker: Rodolfo Panerai

Slides 4_Rodolfo_Panerai.pdf

15:15 Instanton counting for Class S_k

Speaker: Thomas Bourton

Slides 5_Thomas_Bourton.pdf

15:30 → 16:00 Coffee break

15:35 → 16:00 Coffee break

15:45 → 16:15 Coffee Break

16:00 → 17:30 Parallel Session: Pheno 5: BSM II (Dark Matter and Neutrinos)

16:00 Energetic $\gamma$-rays from TeV scale dark matter\\[0.1cm] annihilation resummed

The annihilation cross section of TeV scale dark matter particles $\chi^0$ with electroweak charges into photons is affected by large quantum corrections due to Sudakov logarithms and the Sommerfeld effect. We calculate the semi-inclusive photon energy spectrum in $\chi^0\chi^0\to \gamma+X$ in the vicinity of the maximal photon energy $E_\gamma = m_\chi$ with NLL' accuracy in an all-order summation of the electroweak perturbative expansion adopting the pure wino model. This results in the most precise theoretical prediction of the annihilation rate for $\gamma$-ray telescopes with photon energy resolution of parametric order $m_W^2/m_\chi$ for photons with TeV energies.

Speaker: Mr Caspar Hasner (Technical University Munich)

Slides desy2018_HASNER.pdf

16:17 Constraining MSSM Benchmark Scenarios through Vacuum Stability

Since the LHC has not provided us with any hints towards new physics, it is ever more interesting to constrain BSM theories from purely theoretical considerations. Requiring that the electroweak vacuum in any BSM model is at least metastable, can lead to stringent constraints on the parameter space of the model. Many popular extensions of the SM, such as supersymmetry, feature greatly extended scalar sectors. In the resulting high dimensional scalar potential, vacuum decay can happen in many different field directions. Constraints from vacuum decay thus rely on finding all minima of multidimensional scalar potentials which is a nontrivial task even at tree-level. We study the impact of these constraints on the newly proposed benchmark scenarios for the MSSM.

Speaker: Jonas Wittbrodt (DESY)

Slides VacStab_Wittbrodt.pdf

16:34 Dark matter pair-production in the MSSM and simplified dark matter models at the LHC

Dark matter (DM) makes up around 25% of the matter-energy content of our universe today. However, no evidence for a DM particle has been found so far. Supersymmetry adds an ideal candidate, a Weakly Interacting Massive Particle. To avoid its large parameter space with many parameters being unrelated to DM, such as in the Minimal Supersymmetric Standard Model (MSSM), simplified DM models (SDMMs) offer a way to describe only the DM phenomenology while other effects from new particles are neglected. If the DM particle is light enough, it can be produced at particle colliders to study its properties in a controlled way. Thus, for experimental searches to be as efficient as possible, a proper description of these models is required. In my talk, I will present a comparison of DM pair-production at the LHC in the MSSM and SDMMs with s- and t-channel mediators. The comparison involves a scan over the MSSM parameter space, where the differences of the total cross sections and typical kinematical distributions between the different models are studied. All calculations are done at NLO QCD accuracy and the results for the distributions include parton showering in the POWHEG formalism.

Speaker: Dr Christoph Borschensky (Eberhard Karls Universität Tübingen)

Slides Borschensky_DESY2018.pdf

16:54 High Multiplicity Amplitudes and Anharmonic Oscillators

Calculations of multiparticle scattering amplitudes in scalar field theories at high multiplicities exhibit an extremely rapid growth with increasing number of final state particles. This either indicates an end of perturbative behaviour, or possibly even a breakdown of the theory itself. With the discovery of a scalar Higgs boson this has also turned into a problem of the Standard Model. To shed some light on this question we consider the quantum mechanical analogue of the scattering amplitude for multiparticle production in scalar quantum field theory, which corresponds to transitions in the anharmonic oscillator. For potentials both with and without degenerate vacua we show that the amplitude can be written as an exponential. This allows us to study its behaviour at large excitation number where tree-level perturbation theory violates unitarity constraints. We finally discuss possible generalisations to a broader class of quantum mechanical potentials governed by non-perturbative effects.

Speaker: Sebastian Schenk (Heidelberg University)

Slides DESY2018_SS_highmultqm.pdf

17:12 Composite pNGB Dark Matter

Non-minimal composite Higgs (CH) models, with additional Goldstone bosons (GB) beside the Higgs, do not only present a solution to the hierarchy problem but could also shed light on the dark matter (DM) puzzle. A realization of this scenario was presented in (arXiv:1707.07685): The symmmetry breaking structure is $SO(7)/SO(6)$ and the DM is a complex GB, stabilized by an exact $U(1)_{\rm DM}$. The couplings of the top quark break explicitly both the Higgs and the DM shift symmetries, linking the DM and Higgs potentials and predicting direct detection signals of the size currently tested by XENON1T. In this talk we shortly review the main results of (arXiv:1707.07685) and present a new class of CH models, where the main breaking of the DM shift symmetry comes either from the light quarks or from the gauging of the stabilizing $U(1)_{\rm DM}$ symmetry. This naturally explains the null results of direct detection experiments, while featuring an interesting complementary phenomenology.

Speaker: Mr Maximilian Ruhdorfer (Technical University of Munich)

Slides ruhdorfer_DESY_2018.pdf

16:00 → 17:30 Parallel Session: String 4

16:00 A Non-Unitary Surprise

Speaker: Zoltan Laczko

Slides LACZKO_talk.pdf

16:20 Non-perturbative dualities between 6d circular quiver gauge theories

Speaker: Brice Bastian

Slides Bastian-talk.pdf

16:40 Integrable spin chain for stringy Wess-Zumino-Witten models

Speaker: Andrea Dei

Slides DEI_andrea.pdf

17:00 N = 2 AdS_4 backgrounds of massive type IIA

Speaker: Daniel Prins

Slides prins_-_ads4.pdf

16:15 → 17:45 Parallel Session: Cosmo 5: Leptogenesis

16:15 Low-scale leptogenesis with 3 right-handed neutrinos

We provide the first systematic study of the low-scale leptogenesis scenario in the minimal Standard Model extended with 3 right-handed neutrinos having masses at the GeV scale. We highlight and discuss the differences between the 2- and the 3-right-handed neutrino cases, the major qualitative distinction being the possibility, in the latter scenario, of probing part of the parameter space at the LHC. Moreover, 3-right-handed neutrinos allow for the generation of a CP-asymmetry already in the oscillating sterile sector, without the need of relying on flavour asymmetric washout. We quantitatively study the differences between the parameter space of solutions in the two scenarios, highlighting the viability of the models and their testability in current and future experiments, as well as the different impact of the identified solutions in neutrino observables, as for instance in the neutrinoless double beta decay expected rate.

Speaker: Dr Michele Lucente (CP3 - UCLouvain)

Slides DESY2018_Lucente.pdf

16:35 Leptogenesis and light DM in the Scotogenic Model

This talk is based on [arXiv:1806.06864][1]. We will present an extension of the Standard Model, including three right-handed neutrinos $N_i$ and a new Higgs doublet $\Sigma$, all charged under a exact $Z_2$ parity symmetry. This framework is also known as the "Scotogenic model". We will discuss how one can realize the SM neutrino masses + mixing angles and also generate the observed DM density and the baryon asymmetry of the universe (BAU) in this model framework. The DM is suppossed to be a keV right-handed neutrino which is mainly produced via a freeze-in mechanism given by decays of the new scalars. The BAU is generated via Leptogenesis, which relies on two CP violating mechanisms: 1) Oscillations among the RH neutrinos 2) Heavy scalar decays $\Sigma \to N L$ Combining everything, we found a quite constraint parameter region which places an upper bound on the allowed DM mass of $\mathcal{O} (20)\,\mathrm{keV}$ at most. [1]: https://arxiv.org/abs/1806.06864 "arXiv:1806.06864"

Speaker: Mr Sven Baumholzer (Johannes Gutenberg-Universitaet Mainz)

Slides DESY_TH_18_Baumholzer.pdf

16:50 Testable scenarios for leptogenesis

The simplest extension of the SM that can account for neutrino masses consists in the addition of 2 right-handed neutrinos to the SM field content. In addition to the generation of the light neutrino mass and mixing pattern measured in neutrino oscillations, the low scale realization of the model provides an explanation for the matter-antimatter asymmetry of the Universe via ARS leptogenesis, with right-handed neutrino masses in the range [0.1-100] GeV. The heavy states can thus be produced and searched for in neutrinoless double beta decay searches, beam dump experiments, as SHiP or DUNE, and collider experiments as FCC-ee. I will show that for O(GeV) scale right-handed neutrinos, future experimental data can provide sufficient information to predict the matter asymmetry of the universe. Furthermore, the flavor structure of the minimal model is extremely constrained and shows a very interesting correlation with the PMNS CP-phases which opens a new window for leptonic CP violation.

Speaker: Jacobo Lopez Pavon (CERN)

17:10 Low-scale leptogenesis and dark matter

I will discuss extension of the ARS mechanism which can explain dark matter

Speaker: Mr Andrea Caputo (University of Valencia and IFIC)

Slides CaputoDESY2018.pdf

17:25 Thermal DM beyond 100 TeV and Cosmic Rays

Constraining thermal DM above 100 TeV using Indirect Detection experiments is generally accepted to be either irrelevant or technically challenging. Irrelevant, because the unitarity of the S-matrix implies an upper bound on the thermal DM mass of order 100 TeV. Technically challenging, because the electroweak radiative corrections become non-perturbative above 100 TeV. We consider the class of models in which thermal DM annihilates into lighter mediators, themselves decaying into SM particles. In these models, not only the entropy dilution which results from the mediator decay can evade the unitarity bound on the DM mass but also the scaled-down electroweak radiative corrections allow to reliably compute the energy spectra of the SM final states. Considering for definiteness a model of dark U(1) DM, we compute the Indirect Detection constraints coming from various high-energy telescopes observing gamma-rays, neutrinos and charged cosmic-rays, taking into account the full Sommerfeld effects with a finite mediator mass.

Speaker: Yann Gouttenoire (DESY)

18:00 → 19:00 Hertz Lecture

Convener: Markus Diehl

18:00 Imaging Fundamental Processes: Thought, experiment and the accessible universe

Speaker: George Sterman

Slides Sterman.pdf

Video recording https://webcast.desy.de/?p=7196

19:20 → 22:20 Conference dinner

Friday, 28 September

09:00 → 11:00 Plenary Session

Convener: Joerg Jaeckel

09:00 Recent results from heavy flavour physics

Speaker: Jonas Rademacker

Slides Rademacker.pdf

video recording https://webcast.desy.de/?p=8073

09:40 Searching for New Physics with Flavour Observables

Speaker: Thomas Mannel

Slides Mannel.pdf

Video recording https://webcast.desy.de/?p=8076

10:20 Future of Physics Beyond Colliders at CERN

Speaker: Claude Vallée

Slides Vallee.pdf

Video recording https://webcast.desy.de/?p=8078

11:00 → 11:40 Coffee break

11:40 → 13:00 Plenary Session

Convener: Georg Weiglein

11:40 Non-collider BSM

Speaker: Maxim Pospelov

Slides Pospelov.pdf

Video recording https://webcast.desy.de/?p=8080

12:20 Future facilities

Speaker: Matthew McCullough (CERN)

Slides McCullough.pdf

Video recording https://webcast.desy.de/?p=8092

13:00 → 13:10 Closing

13:00 Closing