Higgs, Flavor and Beyond

27 Sept 2022, 00:00 → 30 Sept 2022, 13:20 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. More details can be found on the conference homepage .

The workshop features:

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

 

 

2022_Hertz_Lecture_Poster.pdf

2022-Theorie-Workshop-Poster.pdf

Tuesday, 27 September

12:45 → 13:45 Registration

13:45 → 13:55 Welcome

desy-th-workshop-22-local-info.pdf

14:00 → 16:00 Plenary Session Tuesday

https://desy.zoom.us/j/8029125821?pwd=WE9MT256cm9yVWNiTURpZ3QrcDhLZz09

Convener: Dieter Zeppenfeld (KIT)

14:00 Highlights of SM and Higgs Physics at LHC

Speaker: Marumi Kado (Sapienza)

DESY-TH-2022.pdf

14:40 EFTs - All of BSM in one Parameterization

Speaker: Francesco Riva (University of Geneva)

desy22_riva.pdf

15:20 QCD at the Precision Frontier

Speaker: Gudrun Heinrich (KIT Karlsruhe)

DESY2022_QCD.pdf

16:00 → 16:30 Coffee break

16:30 → 17:50 Plenary Session Wednesday

Convener: Susanne Westhoff (Heidelberg University)

16:30 Top Physics - Precision for Discoveries

Speaker: Malgorzata WOREK (RWTH Aachen University)

MWorek-DESY.pdf

17:10 New Avenues for Machine Learning in HEP

Speaker: David Shih (Rutgers University)

DESY Theory Workshop.pdf

Wednesday, 28 September

09:00 → 11:00 Plenary Session Wednesday

Convener: Sven-Olaf Moch (UNI/TH (Uni Hamburg, Institut fuer Theoretische Physik))

09:00 Experimental Searches at the LHC

Speaker: Greg Landsberg (Brown University)

GL-DESY-2022.pdf

09:40 New Developments in Old Simulation Tools

Speaker: Stefan Höche (Fermi National Accelerator Lab)

DESY_Hoeche-2022.pdf

10:20 Resummation to all orders in QFT - talk cancelled

Speaker: Pier Francesco Monni (CERN)

11:00 → 11:30 Coffee break

11:30 → 12:50 Plenary Session Wednesday

Convener: Milada Margarete Mühlleitner (Karlsruhe Institute of Technology (KIT))

11:30 Model building for ALPs, dark matter and axions

Speaker: Prateek Agrawal (University of Oxford)

Agrawal-DESY-Oct22.pdf

12:10 Higgs Physics - in the SM and beyond

Speaker: Georg Weiglein (T (Phenomenology))

HiggsPhys_DESYTHWS_22.pdf

12:50 → 14:00 Lunch

14:00 → 15:30 Parallel Session Strings: Strings / Mathematical Physics I

Conveners: Craig Lawrie, Markus Dierigl (LMU)

14:00 Magnetic quivers and negatively charged branes

The Higgs branches of the world-volume theories for multiple M5 branes on an $A_k$ or $D_k$-type ALE space are known to host a variety of fascinating properties, such as the small E 8 instanton transition or the discrete gauging phenomena. This setup can be further enriched by the inclusion of boundary conditions, which take the form of $SU(k)$ or $SO(2k)$ partitions, respectively. Unlike the $A$-type case, $D$-type boundary conditions are eventually accompanied by negative brane numbers in the Type IIA brane realisation. While this may seem discouraging at first, I will demonstrate that these setups are well-suited to analyse the Higgs branches via magnetic quivers. Along the way, I will discuss multiple models with previously neglected Higgs branches that exhibit exciting physics and novel geometric realisations.

Speaker: Dr Marcus Sperling (Shing-Tung Yau Center, Southeast University)

Sperling.pdf

14:20 Construction of 4D Minkowski Yang-Mills solutions with non-compact cosets

Yang-Mills theory is at the heart of theoretical physics, but even classical analytic solutions for its equations are in general very hard to be obtained. This makes algebraic and geometric methods to construct such solutions especially important in this context. In this seminar, we will briefly see how equivariant Ansatz and foliation of the Minkowski space via non-compact cosets can be used to construct a class of analytic Yang-Mills solutions, including "kink" solutions that show up as instantons in Euclidean gauge theory. The properties of those solutions are going to be discussed, and some explicit examples will be shown for illustration.

Speaker: Gabriel Picanco (University Hanover)

14:40 Poisson-Lie T-duality defects and target space fusion

Topological defects have long been known to encode symmetries and
dualities between physical systems. In this talk I will show, at the level of the target space, how defects can be used to study a generalized notion of T-duality, known as Poisson-Lie T-duality. This defect in turn provides us with a proposed kernel for the Fourier-Mukai transform implementing Poisson-Lie T-duality on the RR-sector. Finally I will give a brief outlook how these defects allow for a notion of fusion at the level of the target space, which can be elegantly described within the framework of Dirac geometry. Based on 2208.04662 with Saskia Demulder.

Speaker: Thomas Raml (MPP Munich)

Raml.pdf

15:00 Spelling Polygons

An important part of information in evaluating Feynman integrals is the symbol letters (or alphabet) of the integral. This information makes it possible to write the integral as an ansatz of multiple polylogaritms with the letters as arguments. Moreover, the zeros of the letters correspond to the dynamical (Landau) singularities of the integral. In this work we are calculating the dynamical singularities using methods from the realm of generalized hypergeometry and calculate the symbol by factorizing these singularities. The focus will be on one-loop Feynman integrals, but this is mostly a restriction of convenience.

Speaker: Felix Tellander

Tellander.pdf

14:00 → 15:30 Parallel Session Wednesday Cosmo: Cosmology I

Convener: Gilly Elor

2HDMS_presentation_1.pdf

14:00 Gravitational waves from a holographic phase transitions

We study a first order phase transition in the Early Universe and the corresponding production of gravitational waves in a lattice improved holographic model for QCD, in which deconfinement is described as a Hawking-Page phase trsnsition in the holographic picture.

Speaker: Enrico Morgante (JGU Mainz)

Morgante.pdf

14:15 Domain Walls in Models with Extended Higgs Sector

Extended Higgs models such as the 2HDM and the N2HDM can induce topological defects after spontaneous symmetry breaking. In this talk, I will discuss the formation of domain walls arising after the breaking of the discrete symmetries present in the aforementioned models. I will, in particular, discuss the property of localized CP violation inside the domain walls due to a difference in phase between the Higgs doublets.

Speaker: Mohamed Younes Sassi (UNI/TH (Uni Hamburg, Institut fuer Theoretische Physik))

DesyTheoryWorkshopDomainWalls.pdf

14:30 Quantum and Gradient Corrections to False Vacuum Decay on a de Sitter Background

We study the effects of a fixed de Sitter geometry background in scenarios of false vacuum decay. It is currently understood that bubble nucleation processes associated with first order phase transitions are particularly important in cosmology. Considering the geometry of spacetime complicates the interpretation of the decay rate of a metastable vacuum. However, the effects of curvature can still be studied in the particular case where backreaction is neglected. We compute the imaginary part of the action in de Sitter space, including the one-loop and the gradient corrections. We use two independent methodologies and quantify the size of the corrections without any assumptions on the thickness of the wall of the scalar background configuration.

Based on https://arxiv.org/abs/2205.10136

Speaker: Dr Juan S. Cruz (CP3-origins, SDU)

deSitterPTcorrections.pdf

14:45 Resummation and cancellation of the VIA source in electroweak baryogenesis

In electroweak baryogenesis, the asymmetry between matter and antimatter is generated during the electroweak phase transition. Predicting the amount of matter requires a derivation of transport equations for the CP-violating particles. For a long time, two different formalisms were
used in the literature: the semi-classical method and the vev-insertion
approximation. The latter typically yielded a much larger value for the
asymmetry, such that certain models for electroweak baryogenesis were only consistent with observations if the vev-insertion approximation was correct. In this talk, I will argue that the CP-violating source derived in the vev-insertion approximation is a mere artefact, and in fact vanishes completely.

Speaker: Jorinde Marjolein van de Vis (T (Cosmology))

VIACancellationJvdVis.pdf

15:00 Dark sector in Two Higgs Doublet extensions with a Complex Scalar Singlet

Extension of the Two Higgs Doublet model augmented with a complex scalar singlet (2HDMS) is a well motivated candidate for Beyond Standard Model (BSM) Physics. In this talk, we focus on the dark matter (DM) phenomenology of 2HDMS and investigate cases where the singlet develops a vacuum expectation value (vev) and thereby leading to pseudoscalar DM candidate. We perform a parameter scan to study the impact of relic density and direct detection scenarios on the model parameter space for both cases. Some representative benchmarks are chosen for the former case and potential signals at future e+e- colliders are presented.

Speakers: Julia Ziegler (Uni Hamburg), Julia Ziegler (University of Hamburg)

2HDMS_presentation_1.pdf

15:15 Leptogenesis in a Non-Minimal Scotogenic Model

We discuss leptogenesis in a specific scotogenic model, where the Standard Model is extended by scalar and fermionic singlets and doublets charged odd under a $Z_2$ parity. This model is phenomenologically attractive as it is designed to dynamically generate small neutrino masses, provide viable dark matter candidates and also account for the current value of the $(g_{\mu}-2)$ anomaly. In this talk, we discuss the production of a lepton asymmetry via the decays of the heavy fermionic singlets in this model, which is then converted into the observed baryon asymmetry through the sphaleron process. We identify regions of parameter space where successful leptogenesis is compatible with the $(g_{\mu}-2)$ anomaly, lepton-flavour violating decays, such as $\mu \rightarrow e\gamma$, and the relic density of dark matter.

Speaker: Amitayus Banik (University of Würzburg)

Banik_DESY2022.pdf

14:00 → 15:30 Parallel Session Wednesday: Phenomenology I

Convener: Mathieu Pellen (University of Freiburg)

14:00 One-loop electroweak Sudakov logarithms: a revisitation and automation

In order to obtain reliable theoretical predictions for collider physics, radiative corrections have to be computed and taken into account in Monte Carlo simulations. In particular, at high energies, electroweak (EW) radiative corrections are dominated by the so-called EW Sudakov logarithms, which are negative and large in absolute value. In this talk I will present a revisitation of the algorithm of Denner and Pozzorini (DP) for the calculation of one-loop electroweak Sudakov logarithms. With our revisitation, we have added several novelties to the DP algorithm. For instance, we have obtained a substantial improvement of the approximation of those logarithms that are angular dependent. Moreover, we have identified an imaginary term that has been so far omitted in the literature and that instead cannot be neglected for 2 —> n processes with n > 2. I will discuss results that we have obtained in a completely automated approach via the implementation of our revisitation of the DP algorithm in the MadGraph5_aMC@NLO framework. After having discussed the case of one-loop amplitudes I will move to the case of NLO EW corrections to physical observables and cross sections, introducing a new approach for their Sudakov approximation.

Speaker: Davide Pagani (T (Phenomenology))

Sudakov-DESY.pdf

14:15 Multi-emission kernels for parton branching algorithms

We will discuss a novel framework for addressing QCD factorization in the emission of multiple soft or collinear partons. The purpose of this discussion is to allow for a more precise description of hadron collider data and to better handle theoretical uncertainties from parton showers.
We have developed a power counting algorithm in emission amplitudes with the goal of parameterizing the accuracy of different types of parton showers. An example are inaccuracies introduced by iterating single emission amplitudes vs. the use of a multi-emission kernel. Eventually, this approach should pave to way for higher orders in QCD in parton showers.

Speaker: Maximilian Loeschner (T (Phenomenology))

Loeschner-DESY-Theory-2022.pdf

14:30 Electroweak corrections to g+g -> H and H -> gamma+gamma in the singlet extended Standard Model

One of the simplest extensions of the Standard Model (SM) Higgs sector is the Higgs singlet extension in which one adds a singlet to the particle content of the SM. Such models are being studied at the LHC. In the simplest realization of this model, in which the singlet is real, there are two Higgs bosons and only three new parameters, two mixing angles and the mass of the additional Higgs boson. For both Higgs bosons we present results of the NLO (two-loop) electroweak corrections to the main production mechanism through gluon fusion as well as to their decay into two photons for different values of the three parameters. In all cases we discuss the importance of the electroweak corrections.

Speaker: Benjamin Summ

Desy_theory_workshop.pdf

14:45 Precise predictions for the trilinear Higgs self-coupling in the Standard Model and beyond

The investigation of the trilinear self-coupling of the discovered Higgs boson is one of the main goals of particle physics in the near future.
We provide predictions for this coupling, expressed in terms of the coupling modifier $\kappa_\lambda$, incorporating one-loop corrections within arbitrary renormalizable QFTs.
The presented framework allows to apply a wide class of pre- and user-defined renormalization conditions whereas the calculation of all required one-, two- and three-point functions is incorporated in an automated way.
In this talk I motivate precision predictions for $\kappa_\lambda$ in the context of di-Higgs production and the need for their automation.
The basic ingredients of a generic $\kappa_\lambda$ calculation at the one-loop order as well as the features of the resulting computer program are discussed.
I conclude with an outlook on possible applications

Speaker: Martin Gabelmann (T (Phenomenology))

desytheoryws22.pdf

15:00 Semileptonic $b\rightarrow c$ decays with full charm mass dependence at NNLO

My talk will focus on the calculation of the NNLO contributions to
$b\rightarrow c$ decays with full charm mass dependence. For the
semileptonic decay channel $b \rightarrow cl\overline{\nu}$, we obtain
an analytic result which can be compared to previous known results
obtained via expansions in the mass ratio $m_c/m_b$.
I will also give an outlook on the calculation of the hadronic decay
channels $b\rightarrow c\overline{u}d$ and $b\rightarrow c\overline{c}s$, where similar calculation techniques as in the
semileptonic case will be used.

Speaker: Manuel Egner

SLBdecaysManuelEgner.pdf

15:15 Modified TMD Factorization and Sub-leading Power Corrections

Factorization theorems are known to be extremely powerful tools in high-energy particle physics. Processes like SIDIS, Drell-Yan vector-boson production, Higgs-boson production through gluon fusion and $e^+e^-$ to jets and/or hadrons are just some examples of processes that have been thoroughly investigated by applying rigorous factorization formulae. Furthermore, if in these processes the transverse momentum $\textbf{q}_T$ of the vector boson or final-state hadrons is measured, in the limit of small $\textbf{q}_T$, leading-power transverse-momentum-dependent (TMD) factorization is an established tool to obtain further insight into the internal structure of hadrons (like spin and helicity distributions, sea quark contributions) and/or jets involved. However, in order to properly exploit increasingly precise experimental data, it is important to investigate sub-leading contributions. In this talk, we present a novel method to compute next-to-leading-power and next-to-next-leading-power contributions to TMD cross sections. In the specific example of a Drell-Yan process, we show how our analytic results allow us to achieve next-to-next-to-leading logarithmic (NNLL) resummation, recover both the leading-power TMD factorization and collinear factorization expressions up to next-to-next-to-leading order in the small $\textbf{q}_T$ limit and provide a description of the cross section valid also at intermediate $\textbf{q}_T$. The implications for the phenomenological extraction of TMDPDFs are also discussed.

Speaker: Sergio Leal Gómez (Universität Wien)

DESY_THEORY_WORKSHOP_2022.pdf

15:30 → 16:00 Coffee break

16:00 → 17:30 Parallel Session Strings: Strings / Mathematical Physics II

Conveners: Craig Lawrie, Markus Dierigl (LMU)

16:00 Bootstrapping line defects with $O(2)$ global symmetry

Conformal Field Theories (CFTs), which appear as critical points of an array of physical theories, can be studied nonperturbatively by means of the conformal bootstrap. Recent advancements in especially the numerical bootstrap made it possible to obtain extremely precise results for critical exponents in various CFTs. CFTs can be generalized by adding extended objects (defects), which break the conformal symmetry group to a smaller, conformal subgroup. Defects connect different areas of physics: they appear as boundaries and impurities in low-energy condensed matter systems, as well as Wilson and 't Hooft operators in high-energy String Theories.
I will discuss recent work with A. Gimenez-Grau, E. Lauria and P. Liendo in which we explore 1d line defects with an additional $O(2)$ symmetry using the numerical bootstrap. The starting point is an agnostic approach, where we perfom a systematic bootstrap study of correlation functions between two canonical defect operators: the displacement and the tilt. We then move on to study two specific defects: a monodromy line defect and a localized magnetic field line defect. I will highlight the results of the latter one, where we found a series of intriguing cusps which we investigate.

Speaker: Philine Julia van Vliet (T (Stringtheory))

vanVliet.pdf

16:20 Spinning correlators in N = 2 SCFTs: Superspace and AdS amplitudes

We study four-point functions of spinning operators in the flavor current multiplet in four dimensional N = 2 SCFTs, using superspace techniques. In particular we explicitly construct the differential operators relating the different components of the super-correlator. As a byproduct of our analysis, we report the computation of the four-point amplitudes of gluons in bosonic Yang-Mills theories on AdS_5 and we give evidence of an AdS double copy relation between the gluon amplitude and its gravitational counterpart.

Speaker: Andrea Manenti (Uppsala University)

Manenti.pdf

16:40 Black hole impostors from string theory

In this talk I will argue that "black shells", which are spherical brane bubbles enclosing AdS spacetime can mimic black holes. Such bubbles of AdS are generically unstable, but can be stabilized at a finite radius just outside the would-be horizon of the object by dissolved D0 branes and a gas of open strings.These bubbles can arise from brane polarization effects and are natural to expect from string theory. After illustrating key features of black shells that mimic a Schwarzschild black hole, I will describe slowly spinning black shells which mimic a Kerr black hole. Remarkably, they possess a distinct observational signature in the form an independent quadrupole moment that can, in principle, be detected by astrophysical observations. I will then briefly talk about recent progress on the stability/in-stability of these objects, and highlight a highly non-trivial characteristic of these objects that warrants further study.

This talk will be based on a series of papers [1705.10172], [1712.00511], [2110.10542].

Speaker: Suvendu Giri (U. Milano-Bicocca)

Giri.pdf

17:00 Hidden symmetries in 4D $\mathcal{N}=2$ SCFTs

4D $\mathcal{N}=2$ SCFTs obtained from orbifolding $\mathcal{N}=4$ SYM and then performing a marginal deformation exhibit hidden symmetries. Namely, the orbifolding procedure breaks down some actions of the generators coming from $\mathcal{N}=4$. However, by employing a non-trivial co-product involving a (Drinfeld) twist, the actions of the broken generators can be ``restored'' as generators of a hidden symmetry. In my talk I will focus on the particular example of the R-symmetry group of the $\mathbb{Z}_2$ quiver theory $SU(N) \times SU(N)$ in order to demonstrate some novel features of such symmetries. In particular, the hidden symmetry exhibited by this model allows one to relate $\frac{1}{2}$-BPS states of the $\mathcal{N}=2$ SCFTs multiplets reminiscent of $\mathcal{N}=4$ SYM.

Speaker: Hanno Bertle

16:00 → 17:30 Parallel Session Wednesday Cosmo: Cosmology II

Convener: Veronica Guidetti (T (Cosmology))

2HDMS_presentation_1.pdf

16:00 Novel constraints on interacting dark sectors

A vital step toward understanding DM's nature relies on probing (or constraining) DM self-interaction, and how it interacts with the Standard Model (SM) of particle physics or with other dark sectors. An appealing DM model is to consider the presence of an interacting dark sector, i.e. considering that dark matter is gauged under a symmetry group akin to the SM. In the case those gauge fields are light or massless, we would have then two new components: an interacting dark matter (IDM) coupled with dark radiation (DR). Interacting DM is also appealing in the context of solving the so-called $H_0$ and $\sigma_8$ tensions. In this talk, we provide the most up-to-date constraints in dark-matter dark-radiation interaction. We update former CMB and BAO constraints including also BOSS data within the framework of the effective field theory of large-scale structure. We address how an interacting sector can alleviate cosmological tensions, restoring agreement between Planck and lensing data on the value of $S_8$.

Speaker: Henrique Rubira (None)

DESY_22_09_28_IDM.pdf

16:15 Cosmological constraints on the decay of heavy relics into neutrinos

A massive particle decaying into neutrinos in the early Universe is known to be less constrained than if it was decaying into other standard model particles. However, even if the decay proceeds into neutrinos, the latter still inevitably emit secondary particles undergoing electromagnetic interactions that can be probed. We analyse in details how sensitive various cosmological probes are to such secondary particles, namely CMB anisotropies, CMB spectral distortions, and Big Bang Nucleosynthesis. For relics whose lifetime is shorter than the age of the Universe, this leads to original and stringent bounds on the particle's lifetime as a function of its abundance and mass.

Speaker: Dr Marco Hufnagel (ULB)

22_DTW.pdf

16:30 Constraining Single Field Inflation with the SKA

The SKA allows to map the distribution of neutral hydrogen in the Universe over a vast redshift range. The three-dimensional 21cm power spectrum found through this map can be used to perform precision tests not only for several astrophysical phenomena but also for early Universe cosmology. Even considering only a small redshift range it allows to significantly improve current constraints on the Hubble slow-roll parameters when combined with the CMB anisotropies measurement of Planck.

Speaker: Lennart Röver (Universität Heidelberg)

Constraining HSR parameters with the SKA DESY Theory.pdf

16:45 Probing higher order Starobinsky-inflation with CMB and 21cm

Starobinsky (or $R^2$)-inflation is one of the current best-fit models to the Planck measurements. Extending this effective theory of gravity with the additional third order term to $f(R)=M_P^2\left(R+\frac{1}{2M^2}R^2+\frac{c}{3M^4}R^3\right)$ introduces the dimensionless parameter $c$. Using the Planck measurements, we obtain constraints on the parameters of the fundamental Lagrangian and determine the combined sensitivity of next-generation CMB experiments and future neutral hydrogen maps from SKA to third-order gravity and beyond.

Speaker: Benedikt Schosser

Desy_theory_Benedikt_Schosser.pdf

17:00 Dark Matter from Preheating

Dark relics may have been produced from the decay of the primordial inflaton condensate. In this talk I discuss the possibility of producing scalar dark matter during inflation and (p)reheating. I will discuss the production regimes assuming that this scalar couples to the inflaton via a direct quartic coupling and gravity: purely gravitational, weak direct coupling (perturbative), and strong direct coupling (nonperturbative), by comparing both perturbative (Botlzmann) and non-perturbative (Hartree/Lattice) methods. For each regime, I will determine the dark matter phase space distribution, the corresponding relic abundance and derive the corresponding constraints from structure formation by the Lyman-α forest measurements.

Speaker: Mathias Pierre (T (Phenomenology))

DESYTheoryWorkshop2022_MP.pdf

17:15 Cosmic birefringence mediated by dark $U(1)$

A kinetic coupling between photon and dark photon, a massless $U(1)$ gauge boson in the dark sector, transfers the birefringence of dark photon to the observed cosmic birefringence. Regardless of the origin of the dark birefringence, the amplitude and unique frequency-dependence of the cosmic birefringence depends on the kinetic coupling constant and the temperature of dark photon. To explain the reported tantalizing 3.6$\sigma$ hint of cosmic birefringence, the dark photon temperature must exceed 0.84\,{\rm K}, whose contribution to $\Delta N_{\rm eff}$ might be within reach of the CMB Stage-4.

Speaker: Dongwoo Kang (KIAS)

DESY_DWK.pdf

16:00 → 17:30 Parallel Session Wednesday: Phenomenology II

Convener: Mathieu Pellen (University of Freiburg)

16:00 NLO QCD and EW corrections to off-shell tZj production at the LHC

The production of a single top quark in association with a $\mathrm{Z}$ boson ($\mathrm{tZj}$ production) at the LHC is a relevant probe of the electroweak sector of the Standard Model as well as a window to possible new-physics effects. The growing experimental interest in performing differential measurements for this process demands an improved theoretical modelling in realistic fiducial regions. In this article we present an NLO-accurate $\mathrm{tZj}$ calculation that includes complete off-shell effects and spin correlations, combining QCD and electroweak radiative corrections to the LO signal. Integrated and differential cross-sections are shown for a fiducial setup characterized by three charged leptons, two jets, and missing energy.

Speaker: Christopher Schwan (Universität Würzburg)

talk-schwan.pdf

16:15 Soft gluon resummation for the production of four top quarks at the LHC

In this talk we present results for soft gluon threshold resummation applied to the production of four top quarks. Current theoretical predictions include next-to-leading (NLO) strong and electroweak corrections, yielding a relatively large associated systematic error. By considering the matching of the next-to-leading logarithmic (NLL) result to the available NLO result, we achieve NLO+NLL$^\prime$ precision for the total cross section, which in addition to logarithmic terms also takes into account $\mathcal{O}(\alpha_s)$ non-logarithmic terms that do not vanish at threshold. The threshold-resummed result shows an improved scale dependence when compared to the fixed-order calculation.

Speaker: Laura Moreno Valero (University of Muenster)

DESY_TH_LauraMorenoValero.pdf

16:30 One-loop soft anomalous dimension matrices for $t\bar t j$ hadroproduction

We calculate the one-loop corrections to the soft anomalous dimension matrices for the production of a top-antitop quark pair in association with a jet at hadron colliders. This is a step forward towards implementing a procedure for the resummation of soft-gluon emission logarithms for the $t\bar{t}j + X$ hadroproduction process, that will enable the improvement of the accuracy of the $t\bar{t} j + X$ cross-sections, beyond the current degree of knowledge. The latter, so far, has reached the next-to-leading order (NLO) level, complemented by the accuracy of the Shower Monte Carlo approaches used in matching the NLO computations to parton showers (PS) and by merging with samples with a different number of light jets.

Speaker: Bakar Chargeishvili (Universität Hamburg, II Institut für Theoretische Physik)

Soft_ttj.28Sep2022.pdf

16:45 QED soft functions for heavy mesons

Soft functions are universal hadronic matrix elements that appear in factorization theorems for hard exclusive and inclusive processes and contain non-perturbative information about the partonic structure and soft interactions of the particles involved. As such, they form an important ingredient for precision calculations in the Standard Model. The soft function for a heavy meson is traditionally referred to as light-cone distribution amplitude (LCDA) due to its analytic structure in QCD that dictates the momentum support of the light quark in the meson. Previously, QED effects have been neglected in the LCDA definition since they are expected to be small at scales below the heavy meson mass. However, motivated by the increasingly precise measurements at LHCb and Belle II, the inclusion of QED effects has become a major point of interest. In this talk, we analyze the QCD$\times$QED generalized soft function for charmless $B$ decays and discuss how QED effects alter the analytic structure of the soft matrix element and its behaviour under scale evolution. Furthermore, we provide numerical estimates for the first inverse-logarithmic moments of the $B$ meson that appear in physical observables.

Speaker: Jan-Niklas Toelstede (Technical University of Munich)

softQED.pdf

17:00 Inclusive Drell-Yan Production with Leptoquarks: Simulating NLO effects in non-resonant Dilepton Searches

Motivated by the long-standing hints of lepton-flavour non-universality in the $b\longrightarrow c\ell\nu$ and $b\longrightarrow s\ell^+\ell^-$ channels, we study Drell-Yan production at the Large Hadron Collider (LHC) in the context of leptoquarks (LQs). Based on the latest LHC dilepton analyses
corresponding to an integrated luminosity of around $140\,\mathrm{fb}^{−1}$ of proton-proton collisions at $\sqrt{s}=13\,\mathrm{TeV}$, we present improved limits on the scalar LQ couplings that involve heavy quark flavours and light or heavy dileptons. Moreover, we provide the full $\mathcal{O}(\alpha_s)$ corrections to the $pp\longrightarrow\tau^+\tau^-$ process in the presence of gauge vector LQs. In particular, we show that effects beyond the leading order that are related to real QCD emissions are relevant since the inclusion of additional heavy-flavoured jets notably improves the exclusion limits that derive from the high-mass dilepton tails. Within the POWHEG-BOX framework we present a dedicated Monte Carlo code that allows for an on-the-fly signal event generation including all relevant LQ corrections.

Speaker: Mr Stefan Schulte (Max Planck Institute for Physics (MPP))

Schulte_DESY_2022.pdf

17:15 Inverse Hierarchy MFV Quark Dipole

We present a new minimal flavor violation (MFV) scenario in which the up-type quark dipole coupling matrices $C_{uV}^{ij}$, $V=W$ or $B$, are not only diagonal in the mass eigenbasis but also have the eigenvalues that are inversely proportional to the quark masses. Namely, $C_{uV}^{11}$ is the largest Wilson coefficient in the three families. We analyze several aspects of this 'inverse hierarchy MFV quark dipole' model. In the infrared regime, we compare the flavor changing bounds of $K^0-\bar{K}^0$ oscillation and exotic decays of the charged mesons $\pi^+$, $K^+$, $B^+$. Due to the GIM cancellation and the helicity suppression, these bounds are loose for the first generation quark and require $|C_{uV}^{11}|<\mathcal{O}(10){\rm GeV}^{-2}$. In the ultraviolet(UV) theories, the quark dipole operators are induced by the heavy states in the loops. Consequently, the quark masses receive sizable radiative corrections, leading to the light quarks' naturalness problem. In our framework, we provide a type of UV model in which the loop corrections to the mass cancel each other out. As a key part of our phenomenological study, we simulate the $\bar{p}p\rightarrow W h/Zh\rightarrow \gamma\gamma\ell\nu/\ell\ell$ process at the FCC-$hh$ collider. Our simulation shows that the high luminosity precision, $\sqrt{s}=100{\rm TeV}$, $\mathcal{L}=30\;\text{ab}^{-1}$, sets the $C_{uV}$ upper bounds in the ballpark of $5\times 10^{-3}{\rm TeV}^{-2}$ which is almost two orders of magnitude stronger than the existing bounds obtained from LHC dilepton Drell-Yann channel analysis.

Speaker: Di Liu (T (Phenomenology))

IMFV_dipole.pdf

17:45 → 19:00 Hertz Lecture - Hitoshi Murayama

Convener: Christophe Grojean (T (Theorie))

19:00 → 21:00 Conference dinner

Thursday, 29 September

09:00 → 11:00 Plenary Session Thursday

Convener: Fady Adibsamy Bishara (T (Phenomenology))

09:00 Anomalies and other results: flavor physics in LHCb and Belle II

Speaker: Stephanie Hansmann-Menzemer (Physikalisches Institut, Heidelberg University)

DESYTheory_SHM_29092022.pdf

09:40 Survey of lepton-flavoured U(1) extensions

Speaker: Admir Greljo (University of Bern)

Greljo-DESY-short.pdf

10:20 Puzzles in Flavour Physics: getting to the bottom of it

Speaker: Keri Vos

desy_kkvos.pdf

11:00 → 11:30 Coffee break

11:30 → 12:50 Plenary Session Thursday

Convener: Heidi Rzehak (University of Tübingen)

11:30 Electroweak Physics at the LHC

Speaker: Jonas Lindert (University of Sussex)

JL_DESY_Theory_Workshop_22.pdf

12:10 Physics at EIC: nucleon tomography

Speaker: Alexey Vladimirov (Regensburg University)

Vladimirov.pdf

12:50 → 14:00 Lunch

14:00 → 16:00 Parallel Session Strings: Strings / Mathematical Physics III

Conveners: Craig Lawrie, Markus Dierigl (LMU)

14:00 Dynamical Cobordism and a new brane-like defect

The Cobordism Conjecture postulates that the cobordism classes in a consistent theory of quantum gravity should be trivial, possibly predicting new stringy defects. In this light, I will discuss the Dynamical Cobordism induced by the backreaction of a 9-dimensional non-supersymmetric, positive tension domain wall in string theory. Breaking the cobordism symmetry requires a 7-brane defect capping off spacetime. I will provide an explicit description of this defect, in terms of a new non-isotropic solution of the dilaton gravity equations of motion.

Speaker: Andriana Makridou (MPP Munich)

14:20 Parisi-Sourlas supersymmetry in branched polymers

I will discuss the critical physics of a class of disordered (impure) quantum field theories, called random field models. An interesting example comes from 'branched polymers' whose critical properties are described by the random field phi^3 model. Parisi and Sourlas conjectured nearly 40 years ago that these models have a critical point characterized by an emergent supersymmetry and a mysterious 'dimensional reduction' property. In numerical simulations one finds that the conjecture works only under certain conditions. I will demonstrate how this connection works from a textbook like RG flow analysis of random field models.

Speaker: Apratim Kaviraj (T (Stringtheory))

Kaviraj

14:40 Classical Black-Hole Scattering and Gravitational Waves from the Eikonal Exponentiation

The eikonal exponentiation provides a natural strategy to calculate classical gravitational observables directly from the loop-expansion of gravity amplitudes. In this talk I will discuss how the eikonal can be applied to obtain the deflection angle for the collision of two non-spinning black holes. The inclusion of radiation-reaction effects results in an expression with a smooth behavior at high energies, where it agrees with the universal massless result up to O(G3). I will also illustrate how the eikonal can be promoted to an operator combining elastic and inelastic amplitudes in order to calculate all observables associated to the asymptotic states of classical scattering, including the changes in linear and angular momentum for each colliding body.

Speaker: Carlo Heissenberg (Uppsala University)

Heissenberg.pdf

15:00 Coordinate Bethe Ansatz for N=2 SCFTs

The study of spin chains which capture the spectral problem of N=2 SCFTs in the planar limit can shed light on the integrability of 4d gauge theories with less supersymmetry. I investigate the SU(2) subsector of an orbifold daughter of N=4 SYM by using coordinate Bethe Ansatz method. Exact results of the coordinate Bethe ansatz hints an underlying structure such that S-matrix coefficients factorizes and this factorization is closely related to N=4 SYM spin chains in planar limit.

Speaker: Deniz Bozkurt (DESY)

Bozkurt.pdf

15:20 Averaging toroidal orbifolds with torsion

Recently, the correspondence between an ensemble average over two—dimensional Narain conformal field theories and an “exotic” bulk theory of gravity was established by Maloney and Witten and by N. Afkhami-Jeddi, H. Cohn, T. Hartman, and A. Tajdini. This has been generalized to specific torodial orbifolds by N. Benjamin, C. A. Keller, H. Ooguri, and I. G. Zadeh. We test this correspondence further by comparing again averaged (over Narain moduli space) partition functions of more general orbifolds (Z_N x Z_M), where discrete torsion arises, to bulk Chern—Simons partition functions. We are especially interested in the factorisable case (T^2 x T^2 x T^2)/(Z_2 x Z_2) as this directly relates to a Calabi Yau geometry and gives rise to terms in which the structure of the Eisenstein series play an interesting role.

Speaker: Alexandros Kanargias (Mainz University)

Kanargias.pdf

15:40 Hexagonalization of Wilson Loops

The "hexagonalization" procedure arose in the context of integrability in the AdS/CFT correspondence, in order to compute correlation functions in planar N = 4 SYM. This approach, formalized by Basso, Vieira and Komatsu in 2015 is based upon a cutting procedure of the closed string worldsheet that permits to obtain two building blocks that can be "bootstrapped" using the power of the underlying integrable structure. After an introduction, I will review how we can suitably modify the hexagonalization in order to compute correlation functions on non trivial background such as a Wilson loop and the possible links with other well-known integrability techniques.

Speaker: Davide Lai

Lai.pdf

14:00 → 16:00 Parallel Session Thursday Cosmo: Cosmology III

Convener: Hyungjin Kim (T (Cosmology))

14:00 Light-shining-through The Dark Side of the Moon

The dark photon (DP) is a simple and well-motivated candidate for BSM physics. For keV masses or lighter, the sun can potentially produce a large flux of these particles which can be searched for by so-called helioscopes. In this talk, I will discuss the impact of the angular and spectral distribution of solar DPs on these searches. Considering calibration images of the HINODE XRT solar x-ray telescope one can use its precise angular resolution to improve on previous helioscope analysis techniques which were based on pure event counting. I will show that the use of the additional information can boost the constraints by around one order of magnitude. For this, I will also briefly discuss a reevaluation of the literature results on the angular distribution of DPs. Furthermore, I will comment on the use of solar eclipses as exceptionally large helioscopes. Due to the small exposure, these constraints cannot compete with the current searches of transversal DPs and they require a more sophisticated background modeling due to the pollution by real solar x-rays from the corona.

Speaker: Jonas Frerick (T (Theorie))

theory_workshop_frerick.pdf

14:15 The stochastic relaxion

Cosmological relaxation of the electroweak scale provides an elegant solution to the Higgs mass hierarchy problem. In the simplest model, the Higgs mass is scanned during inflation by another scalar field, the relaxion, whose slow-roll dynamics selects a naturally small Higgs vev. In this work we investigate the mechanism in a less conventional regime where the relaxion is subject to large fluctuations during its dynamics. We identify modified stopping conditions for such dynamics of the relaxion and find the new parameter space. In a large region of the parameter space, the relaxion can naturally explain the observed dark matter density in the universe.

Speaker: Aleksandr Chatrchyan (T (Cosmology))

14:30 Axion dark matter with thermal friction

Axion as a non-thermal dark matter could significantly change its cosmological evolution by interacting with a thermalized hidden sector. We study pure hidden Yang-Mills (YM) gauge fields as an example. The hidden YM gauge fields effectively act as friction to the axion field, and it results in the significant dilution of the axion abundance. We present an analytical and numerical understanding of the cosmological evolution of the axion with thermal friction and apply the results to the QCD axion. The dilution of the axion abundance makes the overabundant region of the axion dark matter viable with tuned friction parameters. We also analyze the evolution of the axion density perturbations under friction and briefly discuss its implications in pre- and post-inflationary scenarios.

Speaker: Hyeonseok Seong (Institute for Basic Science)

Axion DM w: thermal friction.pdf

14:45 Dark gauge bosons in neutron stars

In the presence of a feebly-interacting light particle, its signal might leave an imprint on astrophysical observations so one could obtain meaningful constraints on a parametric space. In this talk, I will discuss additional light gauge boson (so called dark gauge boson) cooling of neutron stars and its implications. With the rigorous treatment of the effective field theory prescription and the thermal effect, the relevant couplings of dark gauge bosons to hadrons in medium is derived. Taking into account the several observed data (e.g., the time duration of the neutrino flux of SN1987A, the predicted location of the compact object in the remnant of SN1987A with its inferred x-ray luminosity, and the x-ray point-like source in Cassiopeia A) that match well with the cooling simulations based on the null hypothesis, I will show the implied meaningful constraints on some gauged $U(1)$ extensions of the Standard Model.

Speaker: Seokhoon Yun (University of Padova)

DESY_S.Yun_29.09.22.pdf

15:00 Searching for Gravitational Waves from Axion Detectors

Electromagnetism in curved space time predicts induced magnetic fields arising from gravitational waves (GWs) in the presence of external electric and magnetic fields. Using this fact, it has been suggested to use axion detectors and reinterpret their results to observe high-frequency GWs (above 100 kHz). In this work, we enlarge this novel possibility by considering more general detector geometries inspired by present/future axion experiments such as ADMX-SLIC. Also, to fully appreciate this methodology, we try to find the optimal geometry which maximizes the sensitivity to GWs.

Speaker: Sung Mook Lee (Yonsei U. & CERN)

DESY_SMLEE.pdf

15:15 Model implementations of axion kinetic misalignment

In the last few years, the paradigm of axion kinetic misalignment has attracted attention as a way to account for axion dark matter in the experimentally accessible low$-f_a$ regime. Kinetic misalignment goes beyond the standard misalignment mechanism by assuming that the axion inherits an initial non-zero velocity from early dynamics, which enhances the dark matter relic relative to the standard misalignment mechanism. In this talk, I will present our recent work on specific model-implementations that provide these initial conditions for axion-like-particle (ALP) dark matter. This opens up the possibility that ALP dark matter might be discovered by upcoming ALP searches, which were previously thought unlikely to find dark matter. I will describe the rich interplay between ALP and SM sectors and show how the $[m_a , f_a ]$ ALP parameter space is impacted by constraints on the kick implementation.

Speaker: Philip Soerensen (UNI/TH (Uni Hamburg, Institut fuer Theoretische Physik))

Presentation.pdf

15:30 Gravitational Focusing of wave dark matter

A massive astrophysical object deforms the local distribution of dark matter, resulting in a local overdensity of dark matter. This phenomenon is often referred to as gravitational focusing. In the solar system, the gravitational focusing due to the Sun induces modulations of dark matter signals on terrestrial experiments. We consider the gravitational focusing of light bosonic dark matter with a mass of less than about 10 eV. The wave nature of such dark matter candidates leads to unique signatures in the local overdensity and in the spectrum, both of which can be experimentally relevant. We provide a formalism that captures both the gravitational focusing and the stochasticity of wave dark matter, paying particular attention to the similarity and difference to particle dark matter. Distinctive patterns in the density contrast and spectrum are observed when the de Broglie wavelength of dark matter becomes comparable or less than the size of the system and/or when the velocity dispersion of dark matter is sufficiently small. While gravitational focusing effects generally remain at a few percent level for a relaxed halo dark matter component, they could be much larger for dark matter substructures. With a few well-motivated dark matter substructures, we investigate how each substructure responds to the gravitational potential of the Sun. The limit at which wave dark matter behaves similar to particle dark matter is also discussed.

Speaker: Alessandro Lenoci (T (Cosmology))

Lenoci_DESYTW22.pdf

15:45 The Sensitivity of Spin-Precession Axion Experiments

A leading effort to detect axion dark matter is through its influence on nuclear spins. The
detection scheme involves polarizing a sample of nuclei within a strong static magnetic field and
searching for spin-precession induced by the oscillating axion field. We revisit the signal and noise
in these experiments, finding some key differences with the existing literature. Most importantly,
in the limit where the spin-relaxation time of the material is large compared to the axion coherence
time, we find the signal grows with time even beyond the coherence time. This feature results in
stronger projected sensitivity in spin-precession experiments and increases the viability of detecting
the QCD axion.

Speaker: Jacob Michael Leedom (T (Cosmology))

JML_DESY_Workshop_Cosmo.pdf

14:00 → 16:00 Parallel Session Thursday: Phenomenology III

Convener: Bibhushan Shakya (T (Cosmology))

14:00 New constraints on extended Higgs sectors from the trilinear Higgs coupling

The trilinear Higgs coupling $\lambda_{hhh}$ is a crucial tool to access the structure of the Higgs potential and probe possible effects of physics beyond the Standard Model (SM). Focusing on the Two-Higgs-Doublet Model as a concrete example, I will discuss the calculation of the leading two-loop corrections to $\lambda_{hhh}$, and show that this coupling can be significantly enhanced with respect to its SM prediction in certain regions of parameter space. Taking into account all relevant corrections up to the two-loop level, I will demonstrate that the current experimental bounds on $\lambda_{hhh}$ already rule out significant parts of the parameter space that would otherwise be unconstrained. Finally, I will present a benchmark scenario illustrating the interpretation of the current results and future measurement prospects for $\lambda_{hhh}$.

Speaker: Johannes Braathen (T (Phenomenology))

Braathen_DESYTH2022.pdf

14:15 Constraining the CP character of the Higgs–top-quark interaction

The CP structure of the Higgs boson in its coupling to the particles of the Standard Model is amongst the most important Higgs boson properties which have not yet been constrained with high precision. In this talk, I will explain how existing inclusive and differential Higgs boson measurements from the ATLAS and CMS experiments can be used to constrain the CP nature of the top-Yukawa interaction. Moreover, I will show how machine-learning-based inference can be used to tighten these constraints in the future by exploiting the full kinematic information. At the end of the talk, I will shortly discuss the constraints arising from the measurement of the electron EDM and discuss how much CP violation in the top-Yukawa coupling can contribute to the baryon asymmetry of the Universe.

Speaker: Henning Bahl (None)

2022_09_29_DESY_theory_workshop.pdf

14:30 Portals into Higgs Stability

We address the notorious metastability of the standard model (SM) and promote it to a model building task: What are the new ingredients required to stabilize the SM up to the Planck scale without encountering subplanckian Landau poles?
We tackle this issue in a less common manner, as the SM is minimally extended by vector-like fermions, while no new scalar fields are introduced.
We chart out the corresponding landscape of Higgs stability, and distinguish between portal mechanisms involving only the gauge interactions of BSM fermions or also new Yukawa interactions with the SM Higgs. Several models allow for vector-like fermions in the TeV-range, which can be searched for at the LHC. For nontrivial flavor structure severe FCNC constraints arise which complement those from stability.

Speaker: Tom Steudtner (TU Dortmund)

stability.pdf

14:45 Probing the CP properties of Higgs bosons via transverse polarization at $𝑒^+𝑒^−$ collide

In the CP-violating 2HDM, the CP-violating Higgs to fermions couplings can make an additional loop contribution on the Higgs to gauge bosons couplings. In order to address this aspect, we consider a generic model which has the effective CP-violation structure of the Higgs to gauge bosons couplings. We explore the effect of CP-violation term via the process $𝑒^+𝑒^−→𝐻𝑍,𝑍→𝜇^+𝜇^−$, where the angular distribution of muon pair can be sensitive to the CP-violation structure. In particular, the transverse polarization of the initial beams can be applied to single out the effect of CP-violating term compared to the unpolarized or longitudinally polarized beams. We discuss the set-up and the results for the differential cross section and the asymmetries with respect to the CP-odd observables with transverse polarization, at the future $𝑒^+𝑒^−$ collider with center-of-mass energy 250 GeV.

Speaker: Cheng Li (FTX (FTX Fachgruppe SLB))

desy_theory_chengli.pdf

15:00 Four-top final states as a probe of Two-Higgs-Doublet models

Using a CMS measurement of four top (𝑡𝑡¯𝑡𝑡¯) production in proton-proton collisions we constrain the parameter space of BSM scalar models. We study these effects for models with a generic scalar X with couplings to W-bosons and to top-quarks. We use Monte-Carlo simulators and fast detector simulations to recast the CMS analysis in order to obtain upper limits on the cross section times branching fraction for the production modes 𝑝𝑝→(𝑡𝑡¯,𝑡𝑊,𝑡)+𝑋 with 𝑋→𝑡𝑡¯, where 𝑋 is a new heavy Higgs 𝐻, a pseudoscalar 𝐴 or mixed CP-state. Furthermore we study the impact on Two-Higgs-Doublet models where four top production places constraints on the low 𝑡𝑎𝑛𝛽 region which is of special interest for Baryogenesis.

Speaker: Steven Paasch (FLC (FTX Fachgruppe SLB))

4top_paasch.pdf

15:15 Alternatives to Top-partner scenarios

In traditional models, no matter in SUSY or CHM, top partners are introduced to cancel the top loop contribution to the Higgs quadratic term. However, the lack of evidence for these top partners required increasing fine-tuning in these types of models. To get a natural EWSB model, an alternative is preferred. In this talk, I will present solutions in another direction. Instead of canceling the top loop, we try to cut it off. It implies that the top Yukawa coupling has its sizable strength only in the infra-red, but gets strongly suppressed at high scales due to new interaction and degree of freedom. I will discuss how these new particles could be and how the top Yukawa is modified. The related phenomenology will also be discussed.

Speaker: Yi Chung (Max-Planck-Institut für Kernphysik)

DESY2022_Yi_Chung.pdf

15:30 Predictions for flavorful Z' searches from asymptotic safety

We investigate b→s flavor-anomaly solutions with $U(1)^\prime$ extensions in the framework of asymptotically safe quantum gravity. We study three different $U(1)^\prime$ extensions with vector-like fermions and a scalar field whose vev breaks the new $U(1)^\prime$. The universal contribution of quantum gravity to renormalization group equations (RGEs) of all the gauge and the Yukawa couplings, beyond the Planck scale, ensues interdependent boundary conditions between the Standard Model and the New Physics (NP) couplings during the flow of RGEs from an interactive UV fixed point. As a result, precise measurements of low-energy SM couplings fix the exact values of the NP couplings, and accordingly, the NP mass range can be significantly narrowed down. We confront the models parameter space with the various LHC searches for VL fermions and the new gauge boson Z'. We find a viable parameter space with a potential to probe entirely in LHC Run 3.

Speaker: Abhishek Chikkaballi Ramalingegowda (National Centre for Nuclear Research, Warsaw)

Abhishek_DESY_2022.pdf

15:45 The Axion-Flavor connection

A local flavor symmetry acting on the quarks of the Standard Model can automatically give rise to an accidental global $U(1)$ symmetry which remains preserved from sources of explicit breaking up to a large operator dimension, while it gets spontaneously broken together with the flavor symmetry. Such non-fundamental symmetries are often endowed with a mixed QCD anomaly, so that the strong CP problem is automatically solved via the axion mechanism.
As a bonus, local flavor symmetries can also help to explain the observed pattern of quark masses and intergenerational mixings, providing an intriguing axion-flavor connection.
We illustrate the general features required to realise this scenario, and we discuss a simple construction based on the flavor group $SU(3)\times SU(2) \times U(1)$ to illustrate how mass hierarchies and intergenerational mixings can arise while ensuring at the same time a high quality Peccei-Quinn symmetry.

Speaker: Clemente Smarra (Sissa)

Smarra.pdf

16:00 → 16:30 Coffee break

16:30 → 18:30 Parallel Session Strings: Strings / Mathematical Physics IV

Conveners: Craig Lawrie, Markus Dierigl (LMU)

16:30 Understanding Constraints of Superconformal Symmetry

Supersymmetric conformal field theories have gained huge renewed interest, especially due to the Maldacena conjecture relating N = 4 supersymmetric Yang-Mills theory to type IIB string theory on AdS5 × S5. To gain a better understanding of
these theories it is important to study the implications of the N = 4 superconformal
symmetry in 4 dimensions, PSU(2,2|4), on the observables. In this talk, methods to construct the invariants of four- and higher point correlators under this symmetry group will be discussed. Since the construction focuses on analytic superspace methods, an introduction to this space will be given.

Speaker: Sophie Mueller

Mueller.pdf

16:50 Heterotic de Sitter Vacua, Modular Symmetry, and Stringy Instantons

I will discuss vacua of Heterotic toroidal orbifolds using effective theories consisting of an overall Kahler modulus, the dilaton, and non-perturbative corrections to both the superpotential and Kahler potential that respect target space modular invariance. I will prove a de Sitter no-go theorem for a class of vacua and thereby substantiate a previous conjecture. I will illustrate a loophole in the no-go theorem and determine criteria that allow for metastable de Sitter vacua. Finally, I will identify inherently stringy non-perturbative effects in the dilaton sector that could exploit this loophole and realize de Sitter vacua.

Speaker: Jacob Leedom

Leedom.pdf

17:10 Special functions in field theory and string amplitudes

I will review the types of special functions appearing in Feynman integrals and string amplitudes, and show how multiple polylogarithms (MPLs) and elliptic multiple polylogarithms (eMPLs) appear in both contexts. Next, I will present new work on elliptic modular graph forms (eMGFs), which appear in closed genus-one string amplitudes. These functions can be loosely thought of as single-valued versions of eMPLs. I will illustrate how eMGFs can be studied in the language of iterated integrals, and that many computational techniques are similar from the land of Feynman integrals. Finally, I will compare analytic methods for the computation of Feynman integrals with numerical methods, and touch on some recent developments in the latter area.

Speaker: Martijn Hidding (Uppsala Univeristy)

Hidding.pdf

17:30 Non-hermitian tricriticality: a field theoretical approach

The space of two dimensional quantum field theories can be probed by considering renormalization group flows, whose fixed points are either conformal field theories or trivial theories. Among the conformal field theories there are some models that are unitary (i.e. the inner product in the Hilbert space is non-negative) and some others that are not unitary; although unitarity is usually required in physics, some non-unitary models play a role in statistical physics, when a ”physical” meaning is clarified. This is the case of the Yang-Lee edge singularity, that is a critical point that can be reached from the unitary conformal field theory that corresponds to the critical Ising model, by deform it with an imaginary magnetic field. Its interpretation concerns the Yang-Lee zeros: zeros of the analytic extension of the partition function, designed as a function of the fugacity, promoted to be a complex parameter.
Even if the Yang-Lee edge singularity is the only known case, one should expect that others non-unitary models can be reached in similar way. We study conformal model that corresponds to the tricritical Ising model when deformed by an imaginary magnetic field.

Speaker: Alessio Miscioscia (DESY)

Miscioscia.pdf

17:50 Liouville Field Theory: The demystification of the reflection amplitude and a novel mechanism of spontaneous symmetry breaking

In short, I shows that Liouville Field Theory (LFT) is the effective field theory of a theory with larger non-compact symmetry group which undergoes a novel mechanism of spontaneous symmetry breaking. The famous, but ill-understood, reflection amplitude of LFT acquires a natural explanation in this context and can be derived from a purely representation theoretic viewpoint. Furthermore, this correspondence provides an exact mechanism for the well-known Sl(2,C)-WZW model/LFT correspondence and a possible proof of the AdS_3/CFT_2 correspondence.

Speaker: Nick Nussbaum (University Cologne)

Nussbaum.pdf

16:30 → 18:30 Parallel Session Thursday Cosmo: Cosmology IV

Convener: Gilly Elor

16:30 A new life for sterile neutrino dark matter after the pandemic

We propose a novel mechanism to generate sterile neutrinos $\nu_s$ in the early Universe, by converting ordinary neutrinos $\nu_\alpha$ in scattering processes $\nu_s\nu_\alpha\to\nu_s\nu_s$. After initial production by oscillations, this leads to an exponential growth in the $\nu_s$ abundance. We show that such a production regime naturally occurs for self-interacting $\nu_s$, and that this opens up significant new parameter space where $\nu_s$ make up all of the observed dark matter. Our results provide strong motivation to further push the sensitivity of X-ray line searches, and to improve on constraints from structure formation.

Speaker: Paul Frederik Depta (Max-Planck-Institut für Kernphysik)

Depta_sterile_nu_DESY_2022.pdf

16:45 Two-component WIMP-FIMP dark matter scenarios in a dark U(1)-extended BSM model.

We consider a $U(1)_D$ extension of the Standard Model that accounts for the neutrino masses and study in detail dark matter phenomenology. The model under consideration includes a vector WIMP and a fermion FIMP dark matter candidates and thus gives rise to two-component dark matter scenarios. We discuss different regimes and mechanisms of production and the interplay between neutrino masses and dark matter relic density. We show that the WIMP and FIMP together compose the observed relic density today with comparable contributions. Finally, we study the connection between the dark matter and the gravitational waves originating from the strong first-order phase transition in the scalar sector.

Speaker: Francesco Costa (ITP)

Costa_DESY (3).pdf

17:00 Search for Fermionic Dark Matter using Astrophysical Neutrinos and Quantum Gravitational Decoherence

A model involving quantum gravitationally induced decoherence is proposed to investigate on the properties of fermionic dark matter using astrophysical neutrinos.

The main assumption of the model is that interactions of particles with the spacetime foam violate global quantum numbers such as lepton number and only conserve unbroken gauge quantum numbers.
Hence, if $N$ hypothetical fermionic dark matter species exist transforming as a singlet under $SU(3)_{\mathrm{c}} \times U(1)_{\mathrm{EM}}$, quantum gravity interactions cannot distinguish between neutrinos and these unknown degrees of freedom.

Applying this phenomenological $3 + N$ flavor model to systems of high energy neutrinos shows that these effects lead to a uniform flavor distribution over all neutral fermionic species in an initially pure neutrino beam after sufficiently long distances.
Therefore, fluxes of neutrinos from astrophysical origin are expected to differ drastically from the standard expectation depending on the number of additional dark matter fermions present.

Consequently, future neutrino experiments could provide new clues about the fermionic dark sector.

Speaker: Mr Dominik Hellmann (Technische Universität Dortmund)

hfb22_hellmann.pdf

17:15 Axion and FIMP Dark Matter in a $U(1)$ extension of the Standard Model

In the Standard Model a Dark Matter candidate is missing, but it is relatively
simple to enlarge the model including one or more suitable particles.
We consider in this paper one such extension, inspired by simplicity and
by the goal to solve more than just the Dark Matter issue.
Indeed we consider a local $U(1) $ extension of the SM providing an
axion particle to solve the strong CP problem and including RH neutrinos
with appropriate mass terms. One of the latter is decoupled from the SM
leptons and can constitute stable sterile neutrino DM.
In this setting, the PQ symmetry arises only as an accidental symmetry
but its breaking by higher order operators is sufficiently suppressed to
avoid introducing a large $ \theta $ contribution.
The axion decay constant and the RH neutrino masses are related
to the same v.e.v.s and the PQ scale and both DM densities are determined by
the parameters of the axion and scalar sector.
The model predicts in general a mixed Dark Matter
scenario with both axion and sterile neutrino DM and is characterised by
a reduced density and observational signals from each single component.

Speaker: Sarif Khan (Goettingen University)

talk-DESY.pdf

17:30 Impact of Non-Perturbative Effects in t-channel Simplified Dark Matter Models

A non-minimal dark sector could explain why WIMP dark matter has evaded detection so far. Based on the extensively studied example of a simplified t-channel dark matter model involving a colored mediator, we demonstrate that the Sommerfeld effect and bound state formation must be considered for an accurate prediction of the relic density and thus also when inferring the experimental constraints on the model. We find that parameter space thought to be excluded by LHC searches and direct detection experiments remains viable. Moreover, we point out that the search for bound state resonances at the LHC offers a unique opportunity to constrain a wide range of dark matter couplings inaccessible to prompt and long-lived particle searches.

Speaker: Mathias Becker (TU München)

DESY22_MB.pdf

17:45 Superradiant Production of Heavy Dark Matter from Primordial Black Holes

Spinning black holes (BHs) can efficiently transfer energy to the surrounding environment via superradiance. In particular, when the Compton length of a particle is comparable to the gravitational radius of a BH, the particle's occupation number can be exponentially amplified. In this talk, I will discuss the effect of the primordial-black-hole (PBH) superradiant instabilities on the generation of heavy bosonic dark matter (DM) with mass above 1 TeV. I will show that superradiance can significantly increase the DM density produced by PBHs with respect to the case that only considers Hawking evaporation, and hence lower initial PBH densities are required.

Speaker: Yong Xu (Bethe Center for Theoretical Physics, Universität Bonn)

DESY2022_XU.pdf

18:00 Direct detection of non-galactic dark matter

In this talk, I will discuss the impact of non-galactic dark matter particles in direct detection searches. Firstly, I will emphasize its relevance when the dark matter is light, and scatters elastically off a nucleus or an electron. Secondly, I will discuss the importance of the non-galactic flux when the dark matter scatters inelastically off a nucleus or an electron. For light dark matter, the non-galactic components enhance the sensitivity of experiments, allowing to probe some thermal production mechanisms. For heavy and inelastic dark matter, the non-galactic components allow to test larger mass splittings between the two dark matter states, further constraining the parameter space of selected models, for example of Higgsino dark matter.

Speaker: Gonzalo Herrera (Technical University of Munich, Max-Planck Institute for Physics)

direct_detection_of_non_galactic_dark_matter_Herrera_DESY.pdf

18:15 Hot spot around evaporating primordial black holes

Primordial black holes (PBHs) form via gravitational collapse of large density perturbations during the radiation-dominated epoch. If a PBH have a mass smaller than O(10^9)g, it can completely evaporate before the Big Bang nucleosynthesis (BBN). We consider the case where PBHs once dominate the Universe and realize reheating through Hawking radiation. The thermalization of the high energy particles emitted from PBHs in the dilute plasma is non-trivial, especially when the emitted particles get more and more energetic as the PBH mass decreases such that the Landau–Pomeranchuk–Migdal (LPM) effect becomes important. The interplay among the time scales of dissipation, LPM effect, and the evaporation results in an interesting temperature profile around the evaporating black hole. In this talk, I will discuss the thermalization process of the high energy paritcles from PBH evaporation and the temperature profile around a PBH due to the complication of thermalization.

Speaker: Minxi He (KEK)

formation of hot spot around small pbhs.pdf

16:30 → 18:30 Parallel Session Thursday: Phenomenology IV

Convener: Emmanuel Stamou (TU Dortmund)

16:30 $\texttt{AutoEFT}$: Automating Effective Field Theories

Effective Field Theories provide a framework to parametrise the effects of yet unseen heavy degrees of freedom in a model independent way. While in recent years the interest in higher-dimensional operators has increased, the construction of a complete and minimal set of operators is remarkably challenging. In this talk, I will report on $\texttt{AutoEFT}$, our implementation of a recently proposed group-theoretical algorithm that systematically accounts for the redundancies arising from equations of motion and integration-by-parts identities among the operators. $\texttt{AutoEFT}$ can be applied to phenomenologically relevant theories like the Standard Model or extensions of it, including new light particles and additional symmetry groups.

Speaker: Magnus Schaaf (RWTH Aachen University)

schaaf_magnus_desy_2022.pdf

16:45 Constraints on SMEFT operators using the missing energy + jet signature

We analyze the signature missing energy + jet in the process $pp \rightarrow \nu \bar \nu + \text{jet}$ to derive constraints within the Standard Model Effective Field Theory (SMEFT).
The main focus is on semileptonic four fermion operators, which also have been constrained using conventional high-$p_T$ Drell-Yan data, low energy observables and are connected to the B-Anomalies.
We find that missing energy + jet offers competitive and complimentary constraints.
The scales constrained for present data are $\Lambda \sim 3.5$ TeV, $3.0$ TeV, $2.6$ TeV and $ 1.6 $ TeV for $uc$, $ds$, $db$ and $sb$ respectively.

Speaker: Daniel Wendler (TU Dortmund)

Dwendler_DESY2022.pdf

17:00 To Profile or To Marginalize – A SMEFT Case Study

Global SMEFT analyses have become a key interpretation framework for LHC physics, quantifying how well a large set of kinematic measurements agrees with the Standard Model. This agreement is encoded in measured Wilson coefficients and their uncertain- ties. A technical challenge of global analyses are correlations. We compare, for the first time, results from a profile likelihood and a Bayesian marginalization for a given data set with a comprehensive uncertainty treatment. Using the validated Bayesian framework we analyse a series of new kinematic measurements. For the updated dataset we find and explain differences between the marginalization and profile likelihood treatments.

Speaker: Nina Elmer

DESY_Elmer.pdf

17:15 New methods for studying the Electroweak phase transition

Gravitational waves offer a new way to understand the Higgs via the Electroweak phase transition. The signal from such a transition would, if observed, give crucial information of the underlying physics. Provided that the transition is first-order and proceeds through nucleating bubbles. Yet theoretical predictions of the gravitational-wave spectrum are rife with uncertainties. Large ones at that—spanning several orders of magnitude for some models. Fortunately, many uncertainties can be reduced by using modern EFT techniques. In this talk I give an overview of these results. To be specific, I review state-of-the-art techniques for calculating observables at high temperatures. In addition, I discuss when conventional methods fail, and how far we can trust perturbation theory.

Speaker: Andreas Ekstedt (UNI/TH (Uni Hamburg, Institut fuer Theoretische Physik))

DESYEkstedt.pdf

17:30 Techniques for the model-independent interpretation of hidden particle searches

Hidden particles can help explain many important hints for new physics, but the large variety of viable hidden sector models poses a challenge for the model-independent interpretation of hidden particle searches. We present techniques published in 2105.06477 and 2203.02229 that can be used to compute model-independent rates for hidden sector induced transitions. Adapting an effective field theory (EFT) approach, we develop a framework for constructing portal effective theories (PETs) that couple standard model (SM) fields to generic hidden particles. We also propose a method to streamline the computation of hidden particle production rates by factorizing them into i) a model-independent SM contribution, and ii) a observable-independent hidden sector contribution.

Speaker: Philipp Klose (Bern University)

Klose_DESY.pdf

17:45 Applying AdS/QCD methods to composite Higgs models

In explaining the EWSB, it was postulated that Higgs boson might be a composite state of pNBGs from the breaking of a larger global group. The AdS/CFT correspondence provides a dual theory which is weakly coupled to perform the perturbative calculations, for example the particles spectrum. In applications to QCD-like theories, the AdS/QCD models are developed. In this talk I will introduce a non-Abelian AdS/QCD model. The corresponding meson spectrum is calculated and shows a good agreement with the experimental data.

Speaker: Yang Liu

holographic non-abelian flavour symmetry breaking.pdf

18:00 The Charged Higgs from the Bottom-Up: Probing Flavor at the LHC

We systematically study model-independent constraints on the three generic charged Higgs couplings to $b$-quarks and up-type quarks. While existing LHC searches have focussed on the $tb$ coupling, we emphasize that the LHC plays a crucial role in probing also $ub$ and $cb$ couplings, since constraints from flavor physics are weak. In particular we propose various new searches that can significantly extend the present reach on the parameter space by: i) looking for light charged Higgses that decay into $ub$-quarks, ii) probing charged Higgs couplings to light and top quarks using multi-$b$-jet signatures, iii) looking for single $b$-quarks in low-mass dijet searches, iv) searching for charge asymmetries induced by charged Higgs production via $ub$ couplings.

Speaker: Mustafa Tabet

talk.pdf

18:15 Explaining the anomalies with dark loops

Several anomalies are currently hinting at the presence of new physics effects in the lepton sector of the Standard Model. First of all, neutrino oscillation experiments have clearly established that neutrinos are massive, while on the cosmological side, the existence of dark matter (DM) is robustly settled. Interestingly, other anomalies have recently shown up, mainly involving the muon: the hints observed in $b \to s$ transitions and the muon anomalous magnetic moment. In this talk we introduce an economical yet powerful model that provides an explanation to all these new physics indications. This is achieved thanks to the addition of a dark sector composed of two singlets and two doublets charged under a $Z_2$ symmetry. These ingredients are enough to induce neutrino masses, accommodate the $b \to s \ell \ell$ and muon $g-2$ anomalies, and provide a viable DM candidate, while being compatible with all the relevant experimental constraints. Therefore, this economic scenario takes into account all the unresolved issues in the lepton sector simultaneously and, as a by-product, also addresses the long-standing DM problem.

Speaker: Ricardo Cepedello (University of Würzburg)

Cepedello_DesyWorkshop2022.pdf

Friday, 30 September

09:00 → 11:00 Plenary Session Friday

Convener: Elina Fuchs (CERN)

09:00 From picoseconds to teraseconds: The lifetime frontier of particle physics

Speaker: Felix Kahlhoefer (RWTH Aachen University)

Theory_workshop_3.pdf

09:40 EFTs: the on-shell way

Speaker: Yael Shadmi (Technion, Israel)

shadmi-DESY22-pdf.pdf

10:20 Status of muon g-2 theory

Speaker: Aida El-Khadra (University of Illinois, Urbana-Champain)

El-Khadra_DESY.pdf

11:00 → 11:40 Coffee break

11:40 → 13:00 Plenary Session Friday

Convener: Juergen Reuter (T (Phenomenology))

11:40 Future Prospects - Future Physics - Future Colliders

Speaker: Michelangelo Mangano (CERN)

Mangano_DESY.pdf

12:20 Quantum Field Theory concepts

Speaker: Hitoshi Murayama (University of California Berkeley, Lawrence Berkeley National Laboratory, Kavli IPMU Tokyo)

DESY 2022.pdf

13:00 → 13:07 Closing