DISCRETE 2022

Nov 7, 2022, 8:30 AM → Nov 11, 2022, 5:00 PM Europe/Berlin

Kongresshaus Baden-Baden

Ulrich Nierste (Institut fuer Theoretische Teilchenphysik, KIT CS)

8th Symposium on Prospects in the Physics of Discrete Symmetries

Discrete symmetries meet the Belle Époque: The conference venue Baden-Baden is a 19th century spa town belonging to the UNESCO World Heritage.

Combinations of the discrete symmetries C,P, and T are probed in electroweak processes, Higgs physics, and low-energy precision experiments. New discrete symmetries are postulated to ensure the stability of Dark Matter or to predict the patterns of quark and lepton flavour mixing.  

The conference addresses the role of  these symmetries in the context of

• quark and lepton flavour physics
• strong CP problem and axions
• neutrino physics
• cosmology
• astroparticle physics
• physics beyond the Standard Model
• precision experiments with atoms and molecules
• collider experiments   

Registration extended to October 12, 2022.
Registration fee:  450€
Early registration fee: 400€, until August 15, 2022.

Poster Discrete_2022_poster.pdf Discrete_2022_poster.png

Mon, November 7 ¶

8:30 AM → 9:20 AM Check-in¶

9:20 AM → 9:30 AM Plenary: Welcome¶

welcome_talk_un.pdf

9:20 AM Welcome¶

Speaker: Ulrich Nierste (KIT)

welcome_talk_un.pdf

9:30 AM → 10:30 AM Plenary¶

Convener: Session Chair: Marco Fedele

welcome_talk_un.pdf

9:30 AM Status of the KOTO experiment to search for kaon rare decays¶

We report the status of the KOTO experiment at J-PARC to
search for the decay $K_L\to {\pi }^0\nu \overline{nu}$. The decay is sensitive to new
physics beyond the standard model because the standard model process is highly
suppressed in the decay. The branching ratio is $3\times {10}^{-11}$ with small
theoretical uncertainty in the standard model. We set an upper limit of the
branching ratio at $3\times {10}^{-9}$ with the data collected in 2015. We achieved
the single event sensitivity of $7.2\times {10}^{-10}$ with 3 events observed for the
2016-2018 data analysis. The number of observed events is consistent to the
background estimations, and we introduced new measures against them, and
collected more data in 2019-2021. We will report the status, and the future
prospects including the KOTO step-2 aiming at the discovery of the decay.

Speaker: Hajime Nanjo ( Osaka University)

nanjo_discrete2022.pdf

10:00 AM Discrete Goldstone Bosons¶

In this talk, I will discuss discrete Goldstone bosons
(dGB's), light particles arising from spontaneously broken exact discrete
symmetries. These dGB's are guaranteed to have nonzero masses, while the
associated discrete symmetry protects them from quadratically divergent mass
contributions. The nonzero masses of dGB's arise directly from the discrete
symmetry, without requiring an explicit symmetry breaking mechanism, setting
dGB's apart from other pseudo-Goldstone bosons. After explaining the mass
protection mechanism, I will discuss the generic experimental signals of dGB's.
Below the spontaneous symmetry breaking scale, typically a preserved subset of
the discrete symmetry remains, leading to a telltale signal of degenerate dGB's
being produced simultaneously. Moreover, ratios of multi-scalar production
amplitudes give a probe of the full UV discrete symmetry.

Speaker: Dr Rachel Houtz (Durham IPPP)

DISCRETE_Houtz.pdf

10:30 AM → 11:10 AM Coffee break¶

11:10 AM → 12:10 PM Plenary¶

Convener: Session Chair: João Penedo (University of Lisbon)

welcome_talk_un.pdf

11:10 AM Theory of CP violation in charm physics¶

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Speaker: Dr Stefan Schacht ( University of Manchester)

schacht_discrete_2022.pdf

11:40 AM New results on CPV in charm and bottom at LHCb¶

An overview of the recent CP violation measurements in charm and beauty decays is presented, and an updated determination of CKM angle gamma, charm mixing, and CP-violation parameters using the LHCb measurements.

Speaker: Angelo Carbone (INFN and University of Bologna)

Carbone_discrete_2022_update.pdf

12:10 PM → 2:00 PM Lunch break¶

2:00 PM → 3:30 PM Plenary¶

Convener: Session Chair: Markus Prim

welcome_talk_un.pdf

2:00 PM Flavour anomalies¶

.Hints for the violation of lepton flavour universality (satisfied within the SM) have accumulated in recent years. In particular, deviations from the SM predictions were observed in semi-leptonic B decays (b->sll and b->ctau), in the anomalous magnetic moment of the muon (g-2), in leptonic tau decays and di-electron searches. Furthermore, also the deficit in first row CKM unitarity, known as the Cabibbo Angle Anomaly, can be interpreted as a sign of lepton flavour universality violation. In this talk I review the status of these anomalies and give an overview of the possible interpretations in terms of new physics models.

Speaker: Andreas Crivellin (PSI & UZH)

Crivellin.pdf

2:30 PM ATLAS and CMS Dark Matter searches: results and future opportunities¶

There are many astrophysical observations and cosmological evidence for the existence of dark matter (DM), but little is known of its particle nature. The Standard Model (SM) does not predict its existence, however, numerous theories beyond the Standard Model (BSM) provide viable candidates for DM. Common candidates in many of these theoretical models are the weakly interacting massive particle (WIMP). If DM weakly interacts with the SM it could be produced at the Large Hadron Collider (LHC) experiments, escaping the detector and leaving a large missing transverse momentum as its signature. The ATLAS and CMS experiments have developed a broad search program for DM candidates and their interactions, including resonance searches for mediator particles which would couple DM to the SM, searches with large missing transverse momentum in the final states produced in association with other SM particles (light and heavy quarks, photons, Z and H bosons, as well as additional heavy scalar particles) called mono-X searches. There is a variety of models probed by those searches, including the Higgs portal model where the Higgs boson mediates the interactions between dark and SM sectors, the DM simplified model studying the energy scale of a mediator particle and dark matter particles, and the DM model with extended Higgs sectors (2HDM+a), which is a simplest gauge-invariant extension and provides a rich phenomenology. Many interesting results using the LHC full Run 2 pp collision data collected at 13 TeV have been achieved, in particular, the interpretations are made for various theoretical models and more complex final states. A review of the latest results of the DM searches at the ATLAS and CMS collaborations is presented, with emphasis on the future opportunities in run3 and beyond, including systematic limitations and new trigger schemes.

Speaker: Hassnae El Jarrari (Universite Mohammed V (MA))

ElJarrari_discrete_2022.pdf

3:00 PM Searches for light dark sectors at Belle II, Belle, and BaBar¶

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Speaker: Michael De Nuccio (University of British Columbia)

DISCRETE22_MichaelDeNuccio_DarkSectorAtBFactories.pdf

3:30 PM → 4:00 PM Coffee break¶

4:00 PM → 5:30 PM Plenary¶

Convener: Session Chair Rachel Houtz

welcome_talk_un.pdf

4:00 PM Recent Advancement in Laser Spectroscopy of Antihydrogen and the Progress towards the Measurement of its Gravitational Acceleration¶

The ALPHA experiment at CERN is designed to perform precision measurements of the properties of antihydrogen - the antimatter counterpart of the hydrogen atom. The so-called ALPHA-2 apparatus is dedicated to antihydrogen spectroscopy. Its goal is to test the CPT invariance, a fundamental symmetry of the Standard Model, which requires that the spectra of hydrogen and antihydrogen be identical. The measurement of the long-lived 1S-2S transition is a milestone in this line of research. Recently, the ALPHA collaboration has also reported on the first successful attempt to laser cool a sample of antihydrogen atoms, an important step towards high precision spectroscopy. The so-called ALPHA-g apparatus is currently making progress towards a measurement of the antihydrogen gravitational acceleration. From the experimental point of view, the gravitational interaction of antimatter is a completely unexplored field. Therefore the goal of ALPHA-g is put to test the prediction of the Weak Equivalence Principle in General Relativity, which states that the gravitational acceleration of matter and antimatter be identical. The technical aspects of ALPHA, such as antihydrogen trapping and detection, as well as its physics results, such as laser spectroscopy, are the focus of this talk.

Speaker: Andrea Capra (TRIUMF)

ALPHA_AndreaCapra.pdf

4:30 PM Multi Higgs Doublet Models and symmetries¶

I discuss the usefulness of symmetries in the study of Multi Higgs Doublet Models.

Speaker: Ivo de Medeiros Varzielas

Ivo_Discrete_2022.pdf

5:00 PM Overview of KATRIN Results on the Neutrino Mass and New Physics Searches¶

The KATRIN experiment aims to measure the neutrino mass by precision spectroscopy of tritium β-decay. Recently, KATRIN has improved the upper bound on the effective electron-neutrino mass to 0.8 eV/c² at 90% confidence level [1] and is continuing to take data for a target sensitivity of 0.2 eV/c².
In addition to the search for the neutrino mass, the ultra-precise measurement of the β-spectrum can be used to probe physics beyond the Standard Model.
Some extensions of the Standard Model allow Lorentz invariance violations. Even though strong constraints in the neutrino sector have been set by oscillation experiments, certain Lorentz-invariance-violating parameters can only be accessed using interaction processes. The layout of the KATRIN experiment makes it possible to investigate those parameters which would manifest themselves as a sidereal oscillation of the spectral endpoint [2].
Motivated by a range of anomalies in neutrino physics experiments, the KATRIN data is investigated for an eV-scale sterile neutrino. For this search a model with three active and one sterile neutrino species is considered. A sterile neutrino shows up as a kink-like structure in the electron energy spectrum [3].
The KATRIN data also enables probing the local relic neutrino background by threshold-free neutrino capture on tritium. This process is characterised by an electron peak positioned two times the neutrino mass above the spectral endpoint [4].
Furthermore, general neutrino interactions (GNI) [5] can be investigated through a search for potential shape variations of the β-spectrum. For this purpose, all theoretically allowed interaction terms for neutrinos are combined in one effective field theory. This enables a model-independent description of novel interactions, which could provide small contributions to the weak interaction. Such potential modifications can then be identified in the KATRIN β-spectrum by means of energy-dependent contributions to the rate.

[1] The KATRIN Collaboration. Direct neutrino-mass measurement with sub-electronvolt sensitivity. Nature Physics 18, 160–166, 2022.
[2] The KATRIN Collaboration. Search for Lorentz-Invariance Violation with the first KATRIN data. Arxiv, 2022.
[3] The KATRIN Collaboration. Improved eV-scale sterile-neutrino constraints from the second KATRIN measurement campaign. Phys. Rev. D, 2022.
[4] The KATRIN Collaboration. New Constraint on the Local Relic Neutrino Background Overdensity with the First KATRIN Data Runs. Phys. Rev. Lett., 2022.
[5] Ingolf Bischer and Werner Rodejohann. General neutrino interactions from an effective
field theory perspective. Nuclear Physics B, 947, 2019.

Speaker: Ms Caroline Fengler (KATRIN Collaboration)

KATRIN_BSM_Discrete_Nov22.pdf

6:00 PM → 8:00 PM Welcome reception¶

Tue, November 8 ¶

9:00 AM → 10:30 AM Plenary¶

Convener: Session Chair: Per Osland

welcome_talk_un.pdf

9:00 AM Modular flavour symmetries from the bottom up¶

I discuss the application of modular invariance to the flavour problem from a (mostly) bottom-up perspective. In this framework, Yukawa couplings and mass matrices are obtained from modular forms, which are functions of a single complex number: the modulus VEV $\tau$. This VEV can be the only source of symmetry breaking, so no flavons need to be introduced. When $\tau$ is close to special values (those preserving residual symmetries), a hierarchical fermion mass spectrum can arise for certain field representations. To illustrate this mechanism, a non-fine-tuned model with hierarchical charged-lepton masses is presented. Some of these apparently ad hoc values of $\tau$ turn out to be justified in simple UV-motivated CP-invariant potentials, for which novel CP-breaking minima are found.

Speaker: Joao Penedo (CFTP-IST, Lisbon)

Penedo_Discrete2022.pdf

9:30 AM Modular Flavor Symmetries and CP from the top down¶

The framework of compactified heterotic string theory offers consistent UV completions of the Standard Model of particle physics. In this approach, the existence of flavor symmetries beyond the Standard Model is imperative and the flavor symmetries can be derived from the top down. Such a derivation uncovers a unified origin of traditional discrete flavor symmetries, discrete modular flavor symmetries, discrete R symmetries of supersymmetry, as well as CP symmetry - altogether dubbed the eclectic flavor symmetry.
I will illustrate how the eclectic flavor symmetry is unambiguously computed from the top-down construction, discuss the different arising sources of spontaneous flavor symmetry breaking, and expose possible lessons for bottom-up flavor model building. Finally, I will focus on one explicit example model that provides a successful fit to all available experimental data while giving rise to concrete predictions for so-far undetermined parameters.

Speaker: Andreas Trautner (Max-Planck-Institut für Kernphysik, Heidelberg)

22_DISCRETE_Trautner.pdf

10:00 AM Status of the CKM matrix fits with a focus on Vub and Vcb¶

In this presentation, I will provide an overview on the current knowledge
on the unitarity of the CKM matrix and its constraining power on new
physics contributions. I will further review the current knowledge on the
determination of $V_{ub}$ and $V_{cb}$, whose values constrain together with the
CKM angle $\gamma /{\varphi }_3$ constrain the apex of the unitary triangle. Several
new measurements emerged recently that provide more insights on the
tensions between different determination methods.

Speaker: Dr Markus Prim (University of Bonn)

Prim_StatusOfTheCKMMatrix.pdf

10:30 AM → 11:10 AM Coffee break¶

11:10 AM → 12:10 PM Plenary¶

Convener: Session Chair: Tomas Gonzalo (KIT)

welcome_talk_un.pdf

11:10 AM Lepton Flavour Violation¶

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Speaker: Ann-Kathrin Perrevoort

DISCRETE_Perrevoort.pdf

11:40 AM Charged Lepton Flavour Violation (phenomenology)¶

The discovery of neutrino oscillations is the first laboratory evidence of New Physics beyond the Standard Model.
Oscillating neutrinos necessarily imply that neutrinos are massive and that (neutral) lepton flavour is violated.
A signal of charged lepton flavour violation (cLFV) however so far eludes experimental discovery.
In this talk I will review some phenomenological implications of current experimental bounds (and future sensitivities) on charged lepton flavour violating processes as well as potential future discoveries.
In connection to neutrino masses I will also highlight some phenomenological implications of leptonic CP violation on cLFV observables.

Speaker: Jonathan Kriewald (IJS)

JK_Discrete2022_cLFV.pdf

12:10 PM → 2:00 PM Lunch break¶

2:00 PM → 3:30 PM Astroparticle Physics and cosmology¶

Convener: Chair: Felix Kahlhöfer (KIT)

2:00 PM 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 (University of Goettingen)

sarif_discrete_2022.pdf

2:15 PM Cosmological constraints on decaying axion-like particles¶

Future cosmological probes promise significant progress in probing the dark universe and the related fundamental particles. Their impact is most powerful when we combine cosmological data with astrophysical observations and laboratory experiments. While computational tools are available for such studies, the large number of model parameters and ensuring consistency between data sets can present difficult challenges.
In this talk, I will show how the global-fitting framework GAMBIT can be used to constrain non-thermal axion-like particles (ALPs) with keV-to-MeV masses that decay into photons. For the first time we combine various cosmological and astrophysical constraints in a joint likelihood approach. This ensures the consistency of assumptions and allows us to investigate the entire multi-dimensional parameter space instead of fixing some parameters to benchmark values.
Leaving the ALP abundance and reheating temperature as free parameters, we identify and re-open still viable ALP parameter space -- even slightly improving BBN observables compared to standard cosmology. In this context, I will comment on the additional constraining power from future spectral distortion missions. Our findings demonstrate the important complementarity of astrophysical and cosmological data and encourage the extension of our analysis to models with ALP-matter couplings.

Speaker: Sebastian Hoof (Karlsruher Institut für Technologie)

2022_discrete_hoof.pdf

2:30 PM Exploring dark matter models with global fits¶

The nature of Dark Matter is one of the most fundamental questions of our day, and many new physics models have been developed to accommodate it. In spite of the considerable amount of experiments built to detect Dark Matter particles, none of them have yet provided significant evidence, and thus many of the models of dark matter are severely constrained. Understanding the status of these models in light of the experimental data then becomes a daunting task of exploring systematically and thoroughly their parameter spaces. Global fits are thus the ultimate strategy for this goal, as they provide efficient sampling of multidimensional parameter spaces and combine all constraints in a rigorous statistical manner. In this talk I will present the results of global studies on various models of dark matter: Higgs portal models, simplified models and an effective field theory of dark matter.

Speaker: Tomas Gonzalo (KIT)

Discrete22.pdf

2:45 PM Two-component vector WIMP – fermion FIMP dark matter model with an extended seesaw mechanism¶

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 (University of Göttingen, ITP)

Costa_DISCRETE (2).pdf

3:00 PM Global Fits of vector-mediated simplified models for dark matter¶

Dark matter candidates can arise from a wide range of
extensions to the Standard Model. Simplified models with a small number of new
particles allow for the optimisation and interpretation of dark matter and collider
experiments, without the need for a UV-complete theory. In this talk, I will discuss
the results from a recent GAMBIT study of global constraints on vector-mediated
simplified dark matter models. I will cover several models with differing spins of the
dark matter candidate. Along with these constraints, I will provide new unitarity
bounds from the self-scattering of vector dark matter and discuss their effect on
collider constraints.

Speaker: Christopher Chang (The University of Queensland)

ChristopherChang_DISCRETE_2022.pdf

3:15 PM Atomic responses for Dark matter scattering off electrons with Ge & Xe Detectors¶

Dark matter interaction with the atomic electron is a
well-motivated problem in recent years. As the nature of DM and its
non-gravitational interactions with normal matter are still unknown, instead of
considering a specific, well-motivated method, we are using multi relativistic
random-phase approximation (MCRRPA) and Frozen core approximation (FCA) in
the present study. Recently, the relativistic random-phase approximation (RRPA)
has been applied, with remarkable successes, to photoexcitation and
photoionization of closed-shell atoms and ions of high nuclear charge, such as
heavy noble gas atoms, where the ground state is well isolated from the excited
states. Furthermore, it is desirable from the experimental point of view to determine
which process and kinematic region would be best to constrain a certain type of
DM interaction with electrons or nucleons. For this purpose, one has to rely on
theoretical analysis. In this work, we try to address the above questions using the
atom, Germanium, and Xenon—where most calculations can be carried out using
nonrelativistic effective field theory. Calculation—and study its scattering with
nonrelativistic LDM particles of a MeV to GeV mass range. Also, the energy
transferred by the dark matter particle to the target depends on the reduced mass
of the system. Therefore, the current sensitivity of direct detection experiments is
limited to a few GeV masses of dark matter particles due to their high energy
thresholds for detecting nuclear recoils. The sub-GeV dark matter is a less
explored region and highly motivated for next-generation experiments. In this work,
we are going to present the scattering of light dark matter (LDM) particles with
atomic electrons in the context of nonrelativistic effective field theory. We consider
both contact and long-range interaction between dark matter and atomic electron.
A state-of-the-art many-body method is used to evaluate the SD and SI atomic
ionization cross-sections of LDM-electron scattering. Our new atomic responses
function to be numerically important in a variety of cases and can mold it with any
dark matter velocity distribution, which we identify and investigate thoroughly using
effective theory methods. We then use our atomic responses function to calculate
differential cross sections within 5% error in RRPA and 20% in FCA. Detailed
results will be presented at the meeting. This work was supported by the Ministry
of Science and Technology (MOST) of Taiwan.

Speaker: Dr Mukesh Kumar Pandey (Department of Physics, National Dong Hwa University, Shoufeng, Hualien 97401, Taiwan)

Mukesh_DISCRETE_7112022 copy.pdf

2:00 PM → 3:30 PM BSM collider physics¶

Convener: Chair: Monika Blanke (KIT)

2:00 PM Top quark physics with the ATLAS experiment at the LHC¶

The large top quark samples in top quark pair and single top production have yielded measurements of the production cross section of unprecedented precision and in new kinematic regimes. They have also enabled new measurements of top quark properties that were previously inaccessible, enabled the observation of many rare top quark production processes predicted by the Standard Model and boosted searches for flavour- changing-neutral-current interactions of the top quark, that are heavily suppressed in the SM. In this contribution the highlights of the ATLAS top quark physics program are presented. ATLAS presents in particular new measurements of the production cross section and production asymmetry of highly boosted top quark pairs and of the top quark polarization in t-channel single top production. The recent observation of associated production of a single top quark with a photon completes the list of processes and adds sensitivity to the EW couplings of the top quark. ATLAS furthermore reports strong evidence for the four-top-production process. Strict bounds are also presented of searches for flavour-changing-neutral-current processes involving top quarks.

Speaker: Marino Romano (Bologna (ATLAS))

Romano_discrete2022_v1.pdf

2:15 PM Recent searches for new phenomena with the ATLAS detector¶

Many theories beyond the Standard Model (BSM) have been proposed to address several of the Standard Model shortcomings, such as the origin of dark matter and neutrino masses, the fine-tuning of the Higgs boson mass, or the observed pattern of masses and mixing angles in the quark and lepton sectors. Many of these BSM extensions predict new particles or interactions directly accessible at the LHC. This talk will present some highlights on recent searches based on the the full Run 2 data collected by the ATLAS detector at the LHC with a centre-of-mass energy of 13 TeV. These include searches for leptoquarks and vector-like fermions, new high mass resonances and lepton flavour violating decays, dark sector searches, as well as searches for new phenomena giving unconventional and/or long-lived particle signatures.

Speaker: Matteo Franchini (University of Bologna (IT))

franchini_atlas_parallel.pdf

2:30 PM Features of the Weinberg 3HDM potential¶

The Weinberg model is a Z_2\times Z_2-symmetric
three-Higgs-doublet model (3HDM)} designed to accommodate CP violation in the
scalar sector within a gauge theory, while at the same time allowing for natural
flavour conservation. In this model the coefficients of the potential are taken to be
complex and therefore CP is explicitly violated. With coefficients chosen to be real,
CP can be spontaneously violated via complex vacuum expectation values (vevs).
In the absence of the terms leading to the possibility of CP-violation either explicit
or induced by complex vevs, the potential has two U(1) symmetries. In this case,
spontaneous symmetry breaking would in general give rise to massless states. In a
realistic implementation, those terms must be included, thus preventing the
existence of Goldstone bosons. A scan over parameters, imposing the existence of
a neutral state at 125 GeV that is nearly CP-even, typically results in the existence
of one or two states with masses below 125 GeV that have a significant CP-odd
component. These light states would have a low production rate via the Bjorken
process and could thus have escaped detection at LEP.

Speaker: Prof. Per Osland (University of Bergen)

osland-nov08.pdf

2:45 PM Dark Matter in S3-Symmetric Three-Higgs Doublet Model With Spontaneous CP Violation¶

Models with an extended scalar electroweak sector can have vanishing vacuum expectation values. Such behaviour is a result of an underlying symmetry. If a symmetry prevents couplings between fermions and additional scalars, such scalars could become viable dark matter candidates. We catalogue $S_3$-symmetric three-Higgs-doublet models, based on whether a specific model could possibly accommodate a dark matter candidate. In our study we assume that the dark matter candidate is stabilised by the ${\mathbb{Z}}_2$ symmetry, which survived spontaneous symmetry breaking, and not superimposed over $S_3$. We explore two models; with an without CP violation. These models have a single dark and two active scalar sectors. The dark matter candidate masses, in two cases, are different from the known models with three scalar doublets. After investigating two models in detail, identifying parameters compatible with both theoretical and experimental constraints, we found that the dark matter candidate mass could be within the range of [52.5, 89] GeV or [6.5, 44.5] GeV for a model with CP violation.

Speaker: Anton Kuncinas (CFTP/IST, U. Lisboa)

Kuncinas_S3_3HDM.pdf

3:00 PM Search for New Resonance in the photon and jet final state using CMS data¶

To address the incompleteness of the Standard Model (SM), many models, e.g compositeness, extra dimensions, have predicted the existence of new resonances at the LHC in the final state of a photon and a jet. If such a resonance exists, the signal would appear as a bump on top of the smooth invariant mass distribution of the SM background processes. A search is presented for new resonances decaying to a photon and a jet in proton-proton collisions at a center-of-mass energy of 13 TeV using the data collected by the CMS experiment between 2016 and 2018, corresponding to an integrated luminosity of 138 fb-1

Speaker: Jyoti Babbar

Discrete_Conference.pdf

3:15 PM Near or Far Detectors? A Case Study for Long-Lived Particle Searches at Electron-Positron Colliders¶

We explore the discovery potential for long-lived particles at
the 250-GeV ILC. The goal is to investigate possible gains of a dedicated far
detector over the main detector ILD. For concreteness, we perform our study for
sub-GeV axion-like particles $a$ produced via $e^{+}{e}^{-}\to a\gamma$ or $e^{+}{e}^{-}\to Z\gamma \to (a\gamma )\gamma$ and decaying into pairs of charged leptons.
In the ideal case of zero background and perfect detection efficiency, we find that
far detectors placed in the planned underground cavities or a large cuboid on the
ground can enhance the sensitivity to long-lived pseudo-scalars at best
moderately. On the other hand, the ILD itself is a perfect environment to search for
long-lived particles, due to its excellent angular coverage and radial thickness. For
long-lived particles produced with cross sections of a few picobarns, the ILD could
probe lifetimes up to 300 ns or proper decay lengths up to 100 m in
$250$fb${}^{-1}$ of data. For axion-like particles produced through weak
interactions, the ILC can reach an even higher sensitivity than searches for
displaced vertices in meson decays at \belletwo. Our findings apply similarly to
other proposed electron-positron experiments with a high angular coverage, such
as the FCC-ee and CEPC.

Speaker: Finn Tillinger (Universität Heidelberg; Institut für Theoretische Physik)

DISCRETE_2022_Finn_Tillinger.pdf

2:00 PM → 3:30 PM Quark Flavour¶

Convener: Chair: Ulrich Nierste (Institut fuer Theoretische Teilchenphysik, KIT CS)

2:00 PM Measurements of CP violation at Belle II¶

The first results from the Belle II collaboration related to the determination of CP violation in $B$ decays presented. Both time-dependent and direct CP violation measurements are possible at this next generation $e^{+}{e}^{-}$ $B$ factory. The first determinations of and constraints on all three CKM unitarity triangle angles are presented. Results using data sets equivalent to an integrated luminosity up to 189 fb${}^{-}1$ are used.

Speaker: Dr Pablo Goldenzweig (KIT, ETP)

DISCRETE2022_CPVBelleII_Goldenzweig.pdf

2:15 PM Recent results about lepton flavor universality violation at LHCb¶

The study of lepton flavor universality violation (LFUV) plays an important role in search for new physics beyond standard model and has recently provided some anomalous results. Benefiting from the large datasets available at LHCb, many such measurements have been performed. Some of these measurements have very good precision and play a leading role in their respective world average values. In this talk, I will introduce recent LFUV results from LHCb, with more focus on processes with b->clv transition.

Speaker: Bo Fang (IJCLab(FR))

LFUV_b2clv_LHCb_DISCRETE2022_bfang.pdf

2:30 PM B-anomalies in a twin Pati-Salam theory of flavour¶

The vector leptoquark $U_1(3,1,2/3)$ is the only single mediator which can simultaneously address the anomalies in $B$-physics. Remarkably, such explanation of the $B$-anomalies requires a hierarchy in the $U_1$ couplings which may be connected with the well-known hierarchies in the masses of the SM fermions. In this direction, a twin Pati-Salam model was recently proposed, in which the $U_1$ couplings and the SM Yukawa couplings find a common origin via mixing of chiral quarks and leptons with vector-like fermions, providing a direct link between the $B$-anomalies and the fermion masses and mixing. I will present a simplified version of the model with three vector-like fermion families, in the massless first family approximation, and show that the second and third family charged fermion masses and mixings and the $B$-anomalies can be simultaneously explained and related. I will show that the model recovers the phenomenology of 4321 models at low-energies, being compatible with all known low-energy data, and I will highlight predictions in promising observables such as $\tau \to 3\mu$, $\tau \to \mu \gamma$ and $B\to K^{(\ast )}\nu \overline{\nu }$ at Belle II and LHCb. Finally, I will discuss high-$p_T$ signals of the rich spectrum of new particles at the TeV scale, comprising the vector leptoquark $U_1$, a coloron $g^{\prime }$ and $Z^{\prime }$, as well as vector-like quarks and leptons with masses also around the TeV scale.

Speaker: Mario Fernández Navarro (University of Southampton)

DISCRETE2022_MFN.pdf

2:45 PM Recent Belle II results related to lepton universality and flavour violation¶

This talk presents recent Belle II results on lepton flavor universality and flavour violation tests using B meson and tau decay.
The low-background collision environment along with the possibility of partially or fully reconstructing one of the two B mesons in the event offer high precision measurements of B decays or rare decays with missing energy. Results from semileptonic and electroweak penguin decay will be discussed. Similar advantages exist for rare tau decay searches. A search for the lepton number violating decays tau -> l alpha is also presented.

Speaker: Marcel Hohmann (U Melbourne)

Discrete2022-MarcelHohmann-v2.pdf

3:00 PM Scalar FCNC and CP violating mixing matrices from the vacuum¶

In the context of a class of two Higgs doublet models where CP violation only arises spontaneously, a possible connection between CP violations in the quark and lepton sectors (described by the CKM and PMNS matrices) is analysed. The important role of scalar flavour changing couplings (SFCNC) in this type of scenario is also discussed in detail.

Speaker: Miguel Nebot Gomez (U. of Valencia - IFIC)

Nebot_CKM-PMNS_Discrete2022.pdf

3:15 PM B0 − ̄B0 entanglement for an ideal experiment for the direct CP violation φ3=γ phase¶

B0– ̄B0 entanglement offers a conceptual alternative to the single charged B-decay asymmetry for the measurement of the direct CP-violating γ=φ3 phase. With f=J/ΨK_L ; J/ΨK_S and g=(ππ)0; (ρ_Lρ_L)0, the 16 time-ordered double-decay rate intensities to (f,g) depend on the relative phase between the f- and g-decay amplitudes given by γ at tree level. Several constraining consistencies appear. An intrinsic accuracy of the method at the level of 1° could be achievable at Belle-II with an improved determination of the penguin amplitude to g channels from existing facilities.

Speaker: Prof. Francisco J. Botella (IFIC (u. Valencia))

Discrete22_Botella_def.pdf

3:30 PM → 4:00 PM Coffee break¶

4:00 PM → 5:30 PM Astroparticle Physics and cosmology¶

Convener: Chair: Thomas Schwetz-Mangold (KIT)

4:00 PM Axion-like particles as mediators for dark matter: beyond freeze-out¶

Recent experimental advances now severely constrain electroweak-scale WIMPs produced via
thermal freeze-out, leading to a shift away from this standard paradigm. Here we consider
an axion-like particle (ALP), the pseudo-Goldstone boson of an approximate U(1) global
symmetry spontaneously broken at a high scale fa, as a mediator between the Standard
model (SM) particles and the dark matter (DM) particles. We explore the case where the
couplings are too small to allow for DM generation via freeze-out and the mediator particle
and the DM constitute a hidden sector which is thermally decoupled from the SM particles.
However, alternative generation mechanisms such as freeze-in and freeze-out from a decoupled
dark sector are now appropriate. Having determined the region of parameter space where
the correct relic density is obtained, we then revisit experimental constraints on ALPs from
electron beam dump experiments, astrophysics and rare B and K decays.

Speaker: Aoife Bharucha (CPT Marseille)

AoifeDISCRETE.pdf

4:15 PM Electroweak Phase Transition in a Dark Sector with CP Violation¶

We investigate the potential of the model 'CP in the Dark'
for providing a strong first-order electroweak phase transition (SFOEWPT) by
taking into account all relevant theoretical and experimental constraints. For the
derivation of the strength of the phase transition we use the one-loop corrected,
daisy-resummed effective potential at finite temperature, implemented in the C++
code BSMPT, to determine the global minimum at the critical temperature. The
model 'CP in the Dark' provides a Dark Matter (DM) candidate as well as explicit
CP violation in the dark sector. We find a broad range of viable parameter points
providing an SFOEWPT. They are within the reach of XENON1T and future
invisible Higgs decay searches for DM. 'CP in the Dark' also offers SFOEWPT
points that display spontaneous CP violation at finite temperature. Having not only
an SFOEWPT that provides the necessary departure from thermal equilibrium, but
also a source of additional non-standard CP violation, opens a promising gate
towards enabling the generation of the baryon asymmetry of the universe (BAU)
through electroweak baryogenesis.

Speaker: Lisa Biermann (Institute for Theoretical Physics, Karlsruhe Institute of Technology)

Biermann_Discrete22.pdf

4:30 PM Modified Dirac equation in schwarzschild metric¶

Heisenberg’s uncertainty principle at the Planck scale leads
to extensions of Dirac equations. In this paper, the generalized uncertainty problem
(GUP) theory is used as an extension of the Dirac equation with the mass term
m_1+iγ^5 m_2 (tachyonic) in the Schwarzschild metric. Its eigenvalue problem for
a particle in a gravitational field created by a central mass is also solved. The
fundamental spinor solution for the tachyonic Dirac equation is found on a helicity
basis. This study shows that it is impossible with current theories to formulate a
covariant equation that could be repulsed by gravity in the framework of space-like
particles.

Speaker: Ms Tara Hassanzadeh (Amirkabir University of Technology)

Presentation.pptx

4:45 PM The cyclic symmetries in the representations of unitary discrete subgroups¶

Dark matter may be stable because of a conserved Z_p (cyclic) symmetry. Usually p is assumed to be 2, but it may also be larger than 2.

This Z_p is usually assumed to be in a direct product with some other symmetry group. The full symmetry group of the theory is then G = Z_p x G'. We suggest another possibility.

Many discrete subgroups of U(n), for any n > 2, have a non-trivial center Z_p, even if they are not the direct product of that Z_p with some other group. When that happens, the irreducible representations (irreps) of the group may either represent all the elements of that Z_p by the unit matrix, or else they may represent that Z_p faithfully. If ordinary matter is placed in a representation where Z_p is represented by 1, and dark matter is placed in irreps that represent Z_p faithfully, then dark matter is stabilized by that Z_p.

We have scanned all the discrete groups in the SmallGroups library with order <2000 that are not the direct product of a cyclic group with some other group. We have determined their centers and whether they are subgroups of one or more groups SU(n) or U(n). We have found that very many groups, especially subgroups of U(n) but not of SU(n), have non-trivial centers Z_p, mostly with p of the form 2^a times 3^b but also with other values of p.

Speaker: Darius Jurciukonis (VU TFAI)

Discrete2022.pdf

5:00 PM CPT and unitarity constraints for higher-order CP asymmetries at finite temperature¶

We use an unconventional diagrammatic approach to formulate CPT and unitarity constraints for higher-order CP asymmetries entering the source term in the Boltzmann equation. Usually, the reaction rate asymmetries in these constraints are computed within the classical kinetic theory, using zero-temperature quantum field theory to describe particles' interactions. We approximate the rates, otherwise obtained within the closed-time-path formalism, in terms of diagrams drawn on a cylindrical surface and their holomorphic cuts. The resulting equilibrium asymmetry constraints incorporate thermal-mass effects and allow tracking the cancelations of reaction rate asymmetries computed with quantum statistics. We use the top Yukawa corrections to the asymmetries in the seesaw type-I leptogenesis as an example. The contribution is primarily based on arXiv:2209.03829.

Speaker: Peter Maták (Comenius University in Bratislava)

PeterMatak.pdf

4:00 PM → 5:30 PM Atoms, nuclei, molecules, and spectroscopy¶

Convener: Chair: Robert Ziegler (University of Freiburg and KIT)

4:15 PM The quantum nature of the "minimal" SO(10) GUT¶

In this talk I will present the latest developments on the minimal potentially realistic non-supersymmetric SO(10) GUT model with the scalar sector consisting of 45+126+10. This model is known to suffer from tachyonic instabilities in the spectrum at tree-level, but quantum corrections to the scalar potential may cure this problem - a route worth investigating, since this particular SO(10) GUT is expected to be inordinately predictive for proton decay. Recently, we completed an analysis of the one-loop corrections to the entire scalar spectrum in the 45+126 context relevant for GUT symmetry breaking, showing that there indeed exist viable non-tachyonic and perturbative regions in the parameter space. Lastly, I will discuss the ongoing analysis of the full model that includes the 10, and issues related to obtaining a suitable EW-scale Higgs doublet for the Yukawa sector.

Speaker: Dr Vasja Susič (Charles University in Prague)

Discrete22_Susic.pdf

4:30 PM New results on the neutron to hidden neutron oscillations hypothesis¶

Neutron to hidden neutron oscillation (n − n') experiments
are one of the several probes for testing the existence of hidden sector worlds [1,
2]. Although hidden states of matter were originally proposed to restore, on a
general picture, the breaking of P and CP symmetries [4], currently they also
correspond to candidates for dark matter [3]. In this work, we present a new
experimental technique with ultra-cold neutrons (UCN) to test n − n' in the range of
intermediate mass splitting. The experiment, which took place at the ILL's PF2
UCN source in 2020, used magnetic fields in the range [50 − 1130] µT to suppress
the degeneracy-lifting energy difference. The preliminary analysis indicated no
presence of n − n' signals, but lead to a new exclusion region of the parameter
space, written as τ_nn 0 > 1 s for |δm| ∈ [2 − 69] × 10 −12 eV (95% C.L.). [1] C.
Abel et al. “A search for neutron to mirror-neutron oscillations using the nEDM
apparatus at PSI”. In: Physics Letters B 812 (2021), p. 135993. doi:
https://doi.org/10.1016/j. physletb.2020.135993. [2] H. Almazán et al. “Searching
for Hidden Neutrons with a Reactor Neutrino Experiment: Constraints from the
STEREO Experiment”. In: Phys. Rev. Lett. 128 (6 Feb. 2022), p. 061801. doi:
10.1103/PhysRevLett.128.061801. [3] R. Foot. “Mirror dark matter: Cosmology,
galaxy structure and direct detection”. In: In-ternational Journal of Modern Physics
A 29.11n12 (2014), p. 1430013. doi: 10 . 1142 / S0217751X14300130. [4] T. D.
Lee and C. N. Yang. “Question of Parity Conservation in Weak Interactions”. In:
Phys. Rev. 104 (1 Oct. 1956), pp. 254–258. doi: 10.1103/PhysRev.104.254.

Speaker: William Saenz-Arevalo ( LPC-Caen)

WilliamSaenz_tuesday_atoms_16h3.pdf

4:45 PM Testing the Pauli Exclusion Principle and Collapse models in underground experiments¶

The Pauli Exclusion Principle (PEP) is one of the main
cornerstones of the Quantum Theory. Violation of the PEP, albeit small, could be
motivated by physics beyond the Standard Model which entail extra space
dimensions, violation of the Lorentz invariance, non-commutative space-time.
These scenarios can be experimentally constrained with stat-of-the-art X-ray
spectroscopy, searching for forbidden transition in atomic systems. I shall present
the results of the VIP-2 experiment at LNGS searching for PEP violations; the
impact of this research in relation to quantum gravity models is also discussed.
Finally, the experimental testes of quantum wave-function collapse models done at
LNGS will also be outlined.

Speaker: Dr Fabrizio Napolitano (Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali di Frascati)

napolitano_testing_pauli_principle.pdf

5:00 PM Implications of a matter-antimatter mass asymmetry in Penning-trap experiments¶

Lorentz-invariance, and locality indicate a conservation of CPT in a causal, unitary and Hermitian quantum field theory, implying that fundamental properties of particles and antiparticles should be equal in magnitude. We compare experiments that could test the mass difference between a particle and its antiparticle and pay a special attention to the Penning trap experiments, which test CPT symmetry by comparing the charge-to-mass ratio measured from cyclotron frequencies of proton and antiproton. We point out how the bounds on CPT violation from the kaon oscillation experiment would be magnitudes above its sensitivity. This is shown by mass decomposition of hadrons using the energy-momentum tensor in QCD. Finally, including CPT tests from comparing neutrino and antineutrino oscillation into discussion, we review their hits towards Lorentz-invariance violation and/or non-locality, and how (micro-)causality is broken and possibly restored.

Speaker: Ting Cheng

TingCheng_DISCRETE.pdf

4:00 PM → 5:30 PM Quark Flavour¶

Convener: Chair: Syuhei Iguro (KIT)

4:00 PM Estimating QCD-factorization amplitudes through the SU(3) symmetry¶

A well known technique to determine the decay amplitudes
of non-leptonic B meson processes is QCD factorization. One of the main issues
faced by this procedure is the analytical determination of power suppressed terms,
for instance of annihilation topologies. In this talk we describe the extraction of the
annihilation contributions from data. Our method is based on establishing a set of
rules which allow to transform the SU(3)-invariant description of B decay
amplitudes into pairs of psudoscalar particles and the QCD factorization
decomposition. Our approach provides not only the size of this contributions from
phenomenological considerations but also a formal proof of the maximal number of
degrees of freedom in the SU(3)-invariant, the topological and the
QCD-factorization representations of B decay amplitudes into Pseudoscalar
particles.

Speaker: Dr Gilberto Tetlalmatzi-Xolocotzi (University of Siegen)

QCDF_SU3_discrete_v2.pdf

4:15 PM Higher-Order Electroweak Contributions to Indirect CP Violation¶

The parameter ᵱᵃ is an important measure of the
imbalance between matter and antimatter in the neutral kaon (ᵃ0 and ᵃ¯0)
system. In particular, ᵱᵃ provides a highly sensitive probe of new physics and
plays a critical role in the global fit of the Cabibbo-Kobayashi-Maskawa matrix. As
one of the first discovered sources of ᵃᵄ violation, it has been extensively
measured in experiment to per-mil precision. The theoretical calculation of ᵱᵃ,
however, has historically been plagued by large perturbative errors arising from
charm-quark corrections. These errors were larger than the expected magnitude of
higher-order electroweak corrections in perturbation theory, rendering these
contributions irrelevant. Recently, it was discovered that a simple
re-parameterization of the effective Hamiltonian drastically reduces perturbative
errors, making these higher-order electroweak calculations worth-while. We
present the next-to-leading-logarithm electroweak contributions to ᵱᵃ.

Speaker: Zachary Polonsky (University of Zurich)

Polonsky_DISCRETE22.pdf

4:30 PM Exactly Stable Protons with a Muonic Force¶

Scalar leptoquarks are popular mediators in new physics explanations of the experimental anomalies in $b\to s{\mu }^{+}{\mu }^{-}$ decays and the muon $g-2$; however, the non-observation of charged lepton flavor violation and proton decay impose severe constraints on their interactions. We present a novel protection mechanism in the form of a gauged, lepton-flavored U(1) symmetry, which is broken by a scalar condensate to accommodate neutrino masses with a type-I seesaw. An exact remnant discrete $Z_9$ symmetry renders the proton exactly stable to all orders in the effective field theory expansion. This framework easily accommodates leptoquark explanations of the aforementioned anomalies without the dangerous interactions.

Speaker: Anders Eller Thomsen (University of Bern)

DISCRETE_2022.pdf

4:45 PM Outer Automorphism Anomalies¶

We discuss anomalies associated with outer automorphisms in gauge theories based on classical groups, namely charge conjugations for SU(N) and parities for SO(2r). We emphasize the inequivalence between two versions of charge conjugation for SU(N) symmetries, and also two versions of parity for SO(2r) symmetries. The subgroups that commute with the outer automorphisms are identified. Some charge conjugations can lead to a paradox, which is resolved by the observation that they are anomalous and hence not symmetries. We then discuss anomaly matching conditions that involve the charge conjugations or parities. Interesting examples are given where the charge conjugation is spontaneously broken.

Speaker: Tom Melia (Kavli IPMU)

discrete2022v2.pdf

5:00 PM Neutrino masses, flavor anomalies and muon Undefined control sequence \boldsymbol from dark loops¶

The lepton sector of the Standard Model is at present haunted by several intriguing anomalies, including an emerging pattern of deviations in $b\to s\ell \ell$ processes, with hints of lepton flavor universality violation, and a discrepancy in the muon anomalous magnetic moment. More importantly, it cannot explain neutrino oscillation data, which necessarily imply the existence of non-zero neutrino masses and lepton mixings. We propose a model that accommodates all the aforecited anomalies, induces neutrino masses and provides a testable dark matter candidate. This is achieved by introducing a dark sector contributing to the observables of interest at the 1-loop level. Our setup provides a very economical explanation to all these open questions in particle physics and is compatible with the current experimental constraints.

Speaker: Pablo Escribano (IFIC (CSIC - Univ. Valencia))

Escribano_DISCRETE2022.pdf

Wed, November 9 ¶

9:00 AM → 10:30 AM Plenary¶

Convener: Session Chair: Michael De Nuccio (University of British Columbia)

welcome_talk_un.pdf

9:00 AM Theory of electric dipole moments¶

In this talk, I review recent theoretical progress of electric dipole moments (EDMs). After explaining a new standard model contribution to paramagnetic EDMs that is recently discovered, I discuss indirect constraints on muon and tau EDMs from paramagnetic EDM experiments such as ACME. I also briefly comment on indirect constraints on charm and bottom quark EDMs.

Speaker: Yohei Ema

YEma_DISCRETE2022.pdf

9:30 AM Gravitational wave science with LISA¶

The space-borne interferometer LISA will be sensitive to a variety of mechanisms sourcing gravitational waves in the late and early universe. In this talk we present the status of the LISA mission and summarize the science that LISA will achieve. We discuss in some detail the measurements that will allow LISA to probe BSM physics and cosmology. Particular attention will be dedicated to the gravitational-wave signatures predicted in models with first-order phase transitions, and how well LISA will constrain such signatures.

Speaker: Germano Nardini (Stavanger)

02_discrete22_GNardini.pdf

10:00 AM Probing ultralight dark matter with cold atoms¶

After broad introduction on ultralight DM, I will briefly
discussed issues associated on quality problem and the interplay between
equivalence principle tests of ultralight DM and direct searches through the
oscillation of energy levels, and then I'll demonstrate the potentially surprising
result that oscillation of energy levels would provide us with possibly the best
bound on QCD-axion models. It is basically going to be based on my three recent
papers: Phys.Rev.Lett. 129 (2022) 3, 031301 2201.02042 Phys.Rev.Lett. 129
(2022) 3, 031302 2111.06883 and 2205.12988 and 2 new upcoming publications.

Speaker: Gilad Perez (Weizmann Institute)

Gilad_Perez_Discrete.pdf

10:30 AM → 11:10 AM Coffee break¶

11:10 AM → 12:10 PM Plenary¶

Convener: Session Chair: Stefan Schacht ( University of Manchester)

welcome_talk_un.pdf

11:10 AM Searching for Gravitational Waves from Cosmic Domain Walls¶

I will explore the possibility that theories with unstable
Domain Walls in the Early Universe could be responsible for the generation of a
Gravitational Wave background signal, focusing in particular on the recent signal
detected by Pulsar Timing Arrays experiments, NANOGrav 12.5 years dataset and
International PTA Data Release 2 (IPTA DR2). As an example, a QCD Axion much
heavier than usual might generate such a signal.

Speaker: Alessio Notari

04_Notari_DISCRETE-BADENBADEN2022.pdf

11:40 AM Spontaneous parity violation¶

Parity as prime example of left-right symmetry, is at the core of discrete symmetries, the first one that a child sees. It has played a fundamental role in the development of weak interactions, first with the V-A effective theory and then in the construction of the Standard Model. I show first how the maximal breaking of parity in beta decay was crucial in Weinberg’s classic 1967 paper that completed the SM. I then turn to the idea of spontaneous symmetry breaking of parity in the context of the Left-Right Symmetric Model (LRSM) which led originally to neutrino mass and the seesaw mechanism behind its smallness. I discuss finally how over the years, the LRSM turned into a self-contained, predictive theory of neutrino mass, in complete analogy with the SM as a theory of charged fermion masses.

Speaker: Goran Senjanovic (LMU)

Discrete22.pdf

12:10 PM → 2:00 PM Lunch break¶

2:00 PM → 3:30 PM BSM collider physics¶

Convener: Chair: Martin Lang (Department of Physics)

2:00 PM Searching for new symmetries in the Higgs sector at ATLAS¶

The discovery of the Higgs boson with the mass of 125 GeV confirmed the mass generation mechanism via spontaneous electroweak symmetry breaking and completed the particle content predicted by the Standard Model. Even though this model is well established and consistent with many experimental measurements, it is not capable of solely explaining some observations. Many extensions of the Standard Model introduce additional scalar fields to account for the electroweak symmetry breaking and thereby extra Higgs-like bosons, which can be either neutral or charged. This talk presents recent searches for additional low- and high-mass Higgs bosons, as well as decays of the 125 GeV Higgs boson to new light scalar particles, using LHC collision data at 13 TeV collected by the ATLAS experiment in Run 2.

Speaker: Dominik Duda (MPI Munich (ATLAS))

DISCRETE2022_dduda.pdf

2:15 PM Higgs boson property measurements at the ATLAS experiment¶

Very detailed measurements of Higgs boson properties can be performed with the Run 2 13 TeV pp collision dataset collected by the ATLAS experiment. This talk presents a review of the latest measurements of the Higgs boson properties, including its mass, CP, and differential cross-sections. Furthermore, couplings, including self-coupling measurement using Higgs pair production, combining measurement targeting various production modes and decay channels are reported. Specific results on production mode cross sections, Simplified Template Cross Sections, and their interpretations are presented. These measurements are used to test specific scenarios of physics beyond the Standard Model, as well as its extension in the framework of Effective Field Theories.

Speaker: Chara Kitsaki (National Technical Univ. of Athens (GR))

discrete22_ckitsaki.pdf

2:30 PM Higgs measurements from CMS¶

The data collected by CMS during the LHC Run 2 allow measuring many properties of the Higgs boson. We will review in this talk the recent results from CMS. They include fiducial and differential cross-section measurements, also in the STXS framework, and measurements of di-Higgs production. They can be interpreted in terms of coupling and charge-parity measurements, or in the effective field theory framework.

Speaker: Nicolo Trevisani (KIT - Karlsruhe Institute of Technology (DE))

Trevisani_Discrete-1.pdf

2:45 PM Top physics results from CMS¶

Recent results on the top quark sector related to the test of various discrete symmetries of the standard model will be presented. These include the search for charge asymmetries and violation of charged lepton flavor and charge-parity symmetries, conducted using proton-proton collision data collected by the CMS experiment during 2015–2018. The obtained results are compared with predictions of the standard model towards constraining physics beyond it.

Speaker: Mintu Kumar (Ph.D student)

Discrete 2022_Mintu_kumar_v3.pdf

3:00 PM Single charged Higgs boson production at the LHC¶

A search for charged Higgs may yield clear and direct sign
of new physics outside the realm of the Standard Model (SM). In the Two-Higgs
Doublet Model (2HDM), we investigate two of the main single charged Higgs
production channels at the Large Hadron Collider (LHC), assuming that either h or
H replicates the detected resonance at ∼ 125 GeV; we ponder the practicality of
the associated charged Higgs production through the channel pp → H ± W ∓ and
pp → H ± bj that could have further substantial challenges at the LHC experiments.
Our study in this regard shows that the cross sections can have sizable rates, at
low tanβ so long the condition M H ± < m t − m b is satisfied, in the viable
parameter space. We propose a set of benchmark points with various unexplored
LHC signatures, arising from the aforementioned charged Higgs boson production
in both 2HDM type-I and type-X, to enhance the LHC search for such a particle.

Speaker: Mr Mohamed Ouchemhou (Laboratoire de Physique Fondamentale et Applique Safi, Faculté Polydisciplinaire de Safi, Sidi Bouzid, B.P. 4162, Safi, Morocco.)

Discrete_2022_Ouchemhou_Mohamed.pdf

3:15 PM Charged Dark Matter in Supersymmetric Twin Higgs models¶

Supersymmetric Twin Higgs models allow for naturally low
electroweak scale without much fine-tuning. If the lightest supersymmetric particle
resides in the twin sector, it could be charged under the unbroken twin
electromagnetism. I will consider the twin stau as candidate for dark matter in
these class of models. All experimental constraints, including self-interaction
bounds, are satisfied for wide range of the parameters. However, future direct
detection experiments such as LUX-ZEPELIN will probe most of the parameter
space. The collider signature of this scenario is a light stau which could be
observed at the LHC as a long-lived particle.

Speaker: Michał Łukawski (University of Warsaw)

Lukawski_Chared_DM.pdf

2:00 PM → 3:30 PM High-intensity frontier¶

Convener: Chair: Ann-Kathrin Perrevoort

2:00 PM CP symmetry test at J-PET¶

The Jagiellonian Positron Emission Tomograph (J-PET) is a detector for tests of discrete symmetries as well as for medical imaging. The novelty of the system is based on usage of plastic scintillators for active detection material and trigger-less data acquisition system. The apparatus consists of 192 plastic scintillators read out from both ends with vacuum tube photomultipliers. Positronium being an eigenstate of both the C and P operators is an unique probe to test the CP symmetry. This test is based on determination of polarization of photons from positronium annihilation. This allows exploration of a new class of discrete symmetry odd operators that were not investigated before. The novelty of the experimental setup is based on usage of plastic scintillators as active detection material and trigger-less data acquisition system. In the talk we describe a preliminary result of CP symmetry test at the precision level of ${10}^{-4}$ in a whole available phase-space and experimental techniques developed by the J-PET collaboration.

Speaker: Eryk Czerwiński (Jagiellonian University, Poland)

J-PET_CPV.pdf

2:15 PM Improved test of CPT invariance in ortho-positronium decays at J-PET¶

Search for violation of the symmetry under combined transformation of charge, parity and time reversal in charged leptonic sector can be tested through the non-vanishing expectation value of certain angular correlation operators that are odd under CPT transformation. In this talk we will discuss the experimental approach for a CPT symmetry test by measuring angular correlations between the spin and momenta of photons originating from ortho-positronium (o-Ps$\to$$3\gamma$) decays. This experiment is performed with the J-PET detector which measures a broad range of kinematical configurations of ortho-positronium annihilation into three photons and is the first experiment to determine the full range of the CPT-odd angular correlation. In the first part of the talk, we will present how a novel technique to estimate the spin of ortho-positronium and momenta of annihilation photons for single recorded ortho-positronium event allowed J-PET to measure the expectation value of CPT symmetry odd angular correlation operator at the precision level of 10${}^{-4}$, a factor of three better than the best known previous experimental result. The second part of talk will focus on the new measures and perspectives for J-PET in improving the sensitivity to CPT violating effects beyond the level of 10${}^{-4}$ by increasing the efficiency for detection of photons from ortho-positronium decays by means of using a new 24 Modular J-PET detector and spherical annihilation chamber.

Speaker: Neha Chug

discrete22_nchug.pdf

discrete22_nchug_up.pdf

2:30 PM First direct tests of T and CPT symmetries in transitions of neutral kaons from KLOE-2¶

The comparison of neutral K-meson transition rates between flavour and CP eigenstates is used to perform independent tests of time-reversal T, CP and CPT symmetries. The analysis of 1.7 fb${}^{-1}$ of KLOE data acquired at the DA$\mathrm{\Phi }$NE $e^{+}{e}^{-}$ collider, using ratios of rates of the two classes of processes, $K_S{K}_L\to {\pi }^{\pm }{e}^{\mp }\nu ,3{\pi }^0$ and $K_S{K}_L\to {\pi }^{+}{\pi }^{-},{\pi }^{\pm }{e}^{\mp }\nu$, provides the first direct and model independent tests of T and CPT symmetries in transitions of neutral kaons.

Speaker: Dr Michał Silarski (Jagiellonian University, Poland)

Silarski_DISCRETE2022v2.pdf

2:45 PM Entangled neutral kaons as a tool for precision tests of CPT symmetry and Quantum Mechanics from KLOE-2¶

The process $\varphi \to K_S{K}_L\to {\pi }^{+}{\pi }^{-}{\pi }^{+}{\pi }^{-}$ exhibits the characteristic Einstein–Podolsky–Rosen correlation that prevents both kaons to decay into pairs of charged pions at the same time. This constitutes a formidable tool to test with high precision the quantum coherence of the entangled kaon state, and to search for tiny deviations from the quantum mechanical prediction that may arise in a quantum gravity scenario. The fit to the observed difference of the kaon decay times with decoherence and CPT violation parameters of various phenomenological models will be discussed. The results, based on data sample of about 1.7 fb${}^{-1}$ (∼ 1.7 $\times {10}^9\varphi \to K_S{K}_L$ decays) collected with the KLOE detector at DA$\mathrm{\Phi }$NE, are consistent with no deviation from quantum mechanics and CPT symmetry violation. The measurement technique together with specific data analysis chain will be presented.

Speaker: Prof. Wojciech Wiślicki (NCBJ, Poland)

wislicki_discrete2022.pdf

3:00 PM The P2 Experiment¶

P2 is a precision experiment planned for the Mainz Energy recovering Superconducting Accelerator (MESA) currently under construction. The goal of P2 is to determine the electroweak mixing angle at a four-momentum transfer of Q^2 = 4.5e-3 GeV^2 with a precision of 0.14 %, comparable to existing measurements at the Z pole. The mixing angle is extracted by measuring the protons weak charge exploiting the parity-violating asymmetry in elastic electron-proton scattering. A high precision measurement of the electroweak mixing angle at low energies is sensitive for deviations from the SM’s prediction of the running of the angle and, therefore, for new physics beyond the SM. Reaching the precision goal with the 155 MeV, 150 µA polarized electron beam provided by the MESA facility requires 11000 hours of measurement time using a 60 cm liquid hydrogen target. The detection of several GHz of scattered electrons poses interesting challenges for the experiment and its electronics.

This talk provides an overview of hey features of the P2 spectrometer and the physics motivation behind it.

Speaker: Lars Steffen Weinstock (Johannes Gutenberg University Mainz, Institute for Nuclear Physics)

discrete2022_weinstock.pdf

3:15 PM Status of the MUonE experiment¶

The MUonE experiment aims to measure with extremely high precision the leading-order hadronic contribution to the muon anomalous magnetic moment g-2. This currently represents the largest uncertainty in the theoretical prediction. A first test has been performed in 2021, with prototypes of the silicon sensors and related electronics, the fundamental components of the detector. The collected data are under analysis. The detector assembly and the tests will be carried on during 2022. In 2023 a test run is foreseen to validate the proposed methods and technologies, which will lead to the final proposal of the experiment. The current status and prospects of MUonE will be discussed.

Speaker: Ms Eugenia Spedicato (University of Bologna)

Discrete22.pdf

2:00 PM → 2:45 PM Light new particles¶

Convener: Chair: Alexey Lokhov (KIT)

2:00 PM On Discrete Goldstone Bosons¶

Exact discrete symmetries, if non-linearly realized, can protect a given theory against ultraviolet sensitivity. Quadratic divergences can cancel exactly, while the lightest scalars stemming from spontaneous symmetry breaking are massive without breaking the symmetry. This is at variance with non-linearly realized continuous symmetries, for which the masses of pseudo-Goldstone bosons require an explicit breaking mechanism and enjoy no such protection. The resulting symmetry-protected masses and potentials offer promising physics avenues, both theoretically and in view of the blooming experimental search for ALPs and other BSM particles. We develop this theoretical setup using invariant theory and focusing on the so-called natural minima of the potential. Typically, a subgroup of the ultraviolet discrete symmetry remains explicit in the spectrum, i.e. realized "à la Wigner". This suggests tell-tale experimental signals as a tool to disentangle that explicit low-energy symmetry: at least two degenerate scalars produced simultaneously, plus specific ratios of multi-scalar amplitudes which provide a hint of the full ultraviolet discrete symmetry. Theories displaying exact A4 and A5 symmetries are explored in detail, as illustrative examples.

Speaker: Victor Enguita-Vileta (Universidad Autónoma de Madrid)

[2022-11 DISCRETE] Slides parallel_A5.pdf

2:15 PM Consistent Kinetic Mixing¶

Extensions of the Standard Model (SM) with new Abelian
gauge groups allow for kinetic mixing between the new gauge bosons and the
hypercharge gauge boson, resulting in mixing with the photon. In many models the
mixing with the hypercharge gauge boson captures only part of the kinetic mixing
term with the photon, since the new gauge bosons can also mix with the neutral
component of the $SU(2{)}_L$ gauge bosons. We take these contributions into
account and present a consistent description of kinetic mixing for general Abelian
gauge groups both in the electroweak symmetric and the broken phase. These
contributions are relevant for all hidden photon models in which SM fermions are
charged, like $U(1{)}_{B-L},U(1{)}_{L_i-L_j}$, etc. Based on these results we derive a
low-energy theorem for the couplings of novel Abelian gauge bosons with the
Standard Model Higgs boson from the one-loop kinetic mixing amplitudes.

Speaker: Patrick Foldenauer (IFT Madrid)

discrete_foldenauer.pdf

2:30 PM The importance of quantum loops for astrophysical ALPs¶

We investigate the effect of quantum loops on the theory of
axionlike particles (ALPs) coupled to electrons. Contrary to some statements in the
recent literature, the effective ALP-photon coupling induced by an electron loop
can be sizeable in the plasma of a supernova. We define a general effective
coupling that depends on the kinematics of the specific process in which an ALP
scatters, decays, or is produced. Using this effective coupling, it can be shown that
production of ALPs by loop processes is in fact slightly more efficient than the
respective tree-level processes in a numerical model of SN1987A. We update the
bound on $g_{ae}$ imposed by the observed duration of the neutrino burst of
SN1987A. Moreover, we derive a new bound, which does not exist at tree-level for
ALPs only coupled to electrons, from the non-observation of gamma-rays from
ALP decays directly after the initial neutrino burst was observed in 1987. These are
the leading constraints on $g_{ae}$ in the ALP-mass range of roughly 30 keV to
240 MeV. Using the effective coupling, we furthermore point out that ALP dark
matter coupled to electrons is not stable in the keV mass range due to
loop-induced decays into photons. Large parts of the parameter space that direct
detection experiments are sensitive to are therefore either (i) incompatible with the
assumption of ALPs being dark matter as their lifetime is shorter than the age of
the universe, or are (ii) already excluded by indirect detection searches for x-rays
and gamma-rays as products of ALP decays.

Speaker: Eike Müller (Stockholm University)

EMueller_Discrete2022.pdf

2:45 PM → 3:30 PM Neutrinos¶

Convener: Chair: Alexey Lokhov (KIT)

2:45 PM Neutrino mass hierarchy from the discrete dark matter model¶

We explore a possible explanation for the hierarchy in scale between the atmospheric and solar neutrino mass differences ($|\mathrm{\Delta }{m}_{31}^2|$ and $\mathrm{\Delta }{m}_{21}^2$)
through the presence of two distinct neutrino mass mechanisms from tree-level and one-loop-level contributions. We demonstrate
that the ingredients needed to explain this hierarchy are present in the minimal discrete dark matter mechanism. This scenario is characterized by adding new RH neutrinos and $SU(2)$ scalar doublets to the Standard Model as triplet representations of an $A_4$ flavour symmetry. The $A_4$ symmetry breaking, which occurs at the electroweak scale, leads to a residual ${\mathbb{Z}}_2$ symmetry responsible for the dark matter stability and dictates the neutrino phenomenology. We show that $CP$ breaking in the scalar potential is needed to fit the neutrino mixing angles.

Speaker: Omar Medina (IFIC (CSIC-Universitat de Valéncia))

OmarMedina-Discrete2022.pdf

3:00 PM Radiative Neutrino Mass with GeV Scale Majorana Dark Matter in Scotogenic Model¶

The experimental observations from the colliders
established the standard model (SM), is the most successful phenomenological
framework to explain the non-gravitational interactions of fundamental particles at
high energy. Non-zero neutrino mass and dark matter cast a shadow over its
success. This necessitates the extension of the SM. The most straightforward and
elegant extension of the SM to explain these two phenomena is the Scotogenic
model, where the SM particle spectrum extends with three isospin singlet
right-handed neutrinos and one doublet scalar while all of these being odd under
Z2 symmetry. In this work, we have considered the lightest right-handed neutrino
as the dark matter candidate and freeze-out mechanism for producing observed
dark matter relic density. The charged lepton flavor violation decay processes
constrain the upper side of Yukawa coupling while observed relic density limits the
lower side. We have performed a unique parameterization to attain the highest
possible Yukawa coupling while satisfying LFV and DM constraints. The reduced
number of free parameters and large Yukawa coupling make the model
predictability at lepton colliders very high. Collider phenomenology for possible
signatures performed at lepton colliders and the required luminosities estimated for
detection.

Speaker: Avnish (Institute of Physics, Bhubaneswar, India.)

Discrete2022.pdf

3:30 PM → 4:00 PM Coffee break¶

4:00 PM → 5:30 PM BSM collider physics¶

Convener: Chair: Monika Blanke

4:00 PM Spontaneous CP violation and the Strong CP problem¶

Models of spontaneous CP violation can solve the Strong
CP problem without the need of an anomalous Peccei-Quinn symmetry. In this talk
we review the Nelson-Barr approach, quantifying a peculiar coincidence between
unrelated mass scales that these models must satisfy in order to correctly
reproduce the Standard Model quark masses and CP violation. We investigate the
compatibility between this requirement and the induced radiative corrections to the
neutron electric dipole moment, and with bounds coming from collider, electroweak
and flavor observables.

Speaker: Alessandro Valenti (University of Padova)

AV.pdf

4:15 PM Probing the early universe with displaced new physics at colliders¶

Displaced events at colliders are a promising way, and in a large region of the
parameter space the only way, to test feebly interacting particles, for instance produced through freeze-in. However, if one assumes freeze-in production happens in the standard cosmological history, these decays happen inside the detector only if the dark matter is very light because of the relic density constraint. Here, we argue how displaced events could very well point to freeze-in within a non-standard early universe history. Focusing on the cosmology of inflationary reheating, we explore the interplay between the reheating temperature and collider signatures for minimal freeze-in scenarios. Observing displaced events at the LHC would allow to set an upper bound on the reheating temperature and, in general, to gather indirect information on the early history of the universe.

Speaker: Sam Junius (ULB & VUB)

talk_Discrete_SJ.pdf

4:30 PM Photon-photon fusion and tau g-2 measurement¶

High statistics measurements of light-by-light scattering, made accessible using relativistic heavy-ion beams provide a precise and unique opportunity to investigate extensions of the Standard Model, such as the presence of axion-like particles. This talk presents a series of measurements of such processes performed by the ATLAS Collaboration. New measurements of exclusive dilepton production (electron, muon, and tau pairs) are discussed. Furthermore, the tau-pair production measurements can constrain the tau lepton's anomalous magnetic dipole moment. Presented measurements of muon pairs produced via two-photon scattering processes in hadronic Pb+Pb collisions provide a novel test of strong-field QED by exploiting correlations between the lepton pair and second-order event-plane, which can potentially be a sensitive electromagnetic probe of the quark-gluon plasma. Results are compared with recent theory calculations.

Speaker: Kristof Schmieden (Johannes Gutenberg Universitaet Mainz (DE))

2022-11-09_ALPsAnd_g-2_atATLAS.pdf

4:00 PM → 5:00 PM High-intensity frontier¶

Convener: Chair: Marco Fedele (KIT, TTP)

4:00 PM Implications of the (g−2)μ anomaly on the flavor structure of New Physics¶

The longstanding $(g-2{)}_{\mu }$ anomaly is one of the greatest puzzles in particle physics. If confirmed, it would be a clear indication for physics beyond the Standard Model. We discuss the implications of this anomaly on the flavor structure of its possible New Physics (NP) explanations. In particular, we investigate flavor alignment conditions that NP models need to satisfy in order to both satisfy the $(g-2{)}_{\mu }$ anomaly and, at the same time, be consistent with the tight bounds from $\mu \to e\gamma$. We analyze the problem in general terms within the Standard Model Effective Field Theory, considering the renormalization group evolution of all the operators involved. We show that semileptonic four-fermion operators, which are likely to generate a sizeable contribution to the $(g-2{)}_{\mu }$ anomaly, need to be tightly aligned to the lepton Yukawa couplings and the dipole operators in flavor space. While this tuning can be achieved in specific NP constructions, employing particular dynamical assumptions and/or flavor symmetry hypotheses, it is problematic in a wide class of models with broken flavor symmetries. We quantify this tension both in general terms, and in the context of explicit New Physics constructions.

Speaker: Felix Wilsch (University of Zurich)

discrete_flavor_alignment.pdf

4:15 PM Precision measurements with Kaons at CERN¶

The NA62 experiment at CERN collected the world's largest dataset of charged kaon decays in 2016-2018, leading to the first measurement of the branching ratio of the ultra-rare K+ --> pi+ nu nu decay, based on 20 candidates.
The radiative kaon decay K+ → pi0e+vg (Ke3g) was studied with a data sample of O(100k) Ke3g candidates with sub-percent background contaminations recorded in 2017-2018. The most precise measurements of the branching ratio and of T-asymmetry are achieved.
An analysis of the flavour-changing neutral current K+ -> pi+ mu+ mu- decay, based on about 27k signal events with negligible background contamination collected in 2017 and 2018 with a dedicated pre-scaled di-muon trigger, leads to the most precise determination of the branching ratio and of the form factor.
New preliminary results are obtained from an analysis of the K+ -> pi+ gamma gamma decay using data collected in 2016—2018 with a minimum-bias trigger. The sample, about 15 times larger than the previous largest one, leads to an unprecedented sensitivity. This analysis can be naturally extended to search for the K+ -> pi+ a, a -> gamma gamma process, where a is a short-lived axion-like particle.
An overview of the latest NA62 results and the future prospect of the experiment are presented.
The first observation of the decay K± → π0 π0 μ± ν (K00µ4) by the NA48/2 experiment at the CERN and the preliminary measurement of the branching ratio are also presented. The result is converted into a first measurement of the R form factor in Kl4 decays and compared with the prediction from 1-loop Chiral Perturbation Theory.

Speaker: Letizia Peruzzo (CERN NA62)

Peruzzo_DISCRETE2022_finalVersion.pdf

4:30 PM Physics beyond the SM with the NA62 experiment at CERN¶

The NA62 experiment at CERN took data in 2016–2018 with the main goal of measuring the K+ -> pi+ nu nubar decay. The high-intensity setup and detector performance make NA62 particularly suited for searching new-physics effects from different scenarios involving feebly interacting particles in the MeV—GeV mass range.
Searches for K+→e+N, K+→μ +N and K+→μ+νX decays, where N and X are massive invisible particles, are performed by NA62. The N particle is assumed to be a heavy neutral lepton, and the results are expressed as upper limits of O(10−8)of the neutrino mixing parameter |Uμ4|2. The X particle is considered a scalar or vector hidden sector mediator decaying to an invisible final state. Upper limits of the decay branching fraction for X masses in the range 10–370 MeV/c2 are reported. An improved upper limit of 1.0 x 10−6 is established at 90% CL on the K+→μ+ννv branching fraction.
Dedicated trigger lines were employed to collect dilepton final states, which allowed establishing stringent upper limits on the rates lepton flavor and lepton number violating kaon decays. Upper limits on the rates of several K+ decays violating lepton flavour and lepton number conservation, obtained by analysing this dataset, are presented.
The NA62 experiment can also be run as a beam-dump experiment, by removing the Kaon production target and moving the upstream collimators into a “closed” position. Analyses of the data taken in beam-dump mode were performed to search for visible decays of exotic mediators, with a particular emphasis on Dark Photon Models.

Speaker: Letizia Peruzzo (CERN NA62)

Peruzzo_DISCRETE2022_finalVersion.pdf

4:45 PM The NA64-e experiment at CERN¶

One of the most compelling arguments motivating the search for physics beyond the Standard Model (SM) is the need to explain the nature of Dark Matter (DM). Despite an extensive experimental program that combined direct, indirect, and detection at colliders, to date, no conclusive results about DM particle nature have been determined. Among the DM theories, DM particles in the mass range 1 MeV - 1000 MeV (also called Light Dark Matter or LDM) represent a theoretically well-grounded option if a new DM-SM interaction mechanism is introduced. A simple hypothesis is based on the introduction of a new vector boson (Dark Photon or $A^{\prime }$) interacting with the SM photon (through a feeble kinetic mixing) and with the DM particles. In this scenario, the $A^{\prime }$ can be generated by the interactions of charged particles with ordinary matter and subsequently decays into LDM particle pair.

The NA64-e experiment at CERN exploits the 100 GeV SPS electron beam impinging on a thick active target (an electromagnetic calorimeter) to measure the energy deposited by each incoming particle. If an $A^{\prime }$ is produced in the target, the LDM daughter particles leave the detector without further interactions, resulting in a measurable "missing energy", defined as the difference between the beam and the measured "visible" energy. In this context, NA64 searches for large-missing-energy events in which a null activity in the downstream veto systems is detected. To date, NA64 has collected $2.84\times {10}^{11}$ electrons on target. Zero events with missing energy > 50 GeV and no activity within the veto systems were observed. These results allowed the collaboration to set the most competitive limits in the LDM parameter space.

Recently, a missing energy measurement with a positron-beam has also been considered in NA64-e, connected to the POKER (POsitron resonant annihilation into darK mattER) ERC project. The use of a positron beam allows strongly enhancing LDM production by exploiting the electron-positron annihilation process. This also provides a clean signal signature associated with the underlying resonant reaction dynamics, translating into a peak the missing energy distribution whose position depends solely on the mass of the A’. The growing interest in this new approach motivated the NA64 collaboration to perform a preliminary feasibility study running the experiment with a 100 GeV positron beam in the current experimental setup.

This talk will present the latest NA64-e results, including an update regarding the positron beam run, and the plans for the future activities.

Speaker: Pietro Bisio (INFN-Genova)

DISCRETE_2022_BADEN_BADEN_compressed.pdf

4:00 PM → 5:30 PM Neutrinos¶

Convener: Chair: Thomas Schwetz-Mangold (Karlsruhe Institute of Technology)

4:00 PM Sterile Neutrino Search with the KATRIN Experiment¶

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Speaker: Leonard Köllenberger (IAP, KIT)

2022-11-09-Slides-DISCRETE-Koellenberger.pdf

4:15 PM Hybrid scoto/seesaw: flavour and dark matter¶

I will present our recent work (arXiv:2204.13605 [hep-ph]) based on a hybrid type-II seesaw/scotogenic model supplemented with a discrete flavour symmetry where CP is dynamically generated by the vacuum. Namely, we analyse compatibility with low-energy neutrino observables, review the charged lepton flavour violation implications and study the scalar and fermionic dark matter phenomenology of our framework.

Speaker: Henrique Brito Câmara (CFTP/IST, U. Lisboa)

HBCâmara_DISCRETE_2022_Talk.pdf

4:30 PM Sterile neutrinos along the DUNE decay pipe¶

We analyse the sensitivity of the Deep Underground Neutrino Experiment (DUNE) to a sterile neutrino, combining information from both the Near Detector (ND) and the Far Detector (FD). DUNE's sterile exclusion reach is affected by taking into account the information on the neutrino production point, in contrast to assuming a point-like neutrino source. Visible differences remain after taking into account energy bin-to-bin uncorrelated systematics.

Speaker: Joao Pulido

pulido_discrete_2022.pdf

4:45 PM Latest results from the CUORE experiment¶

The Cryogenic Underground Observatory for Rare Events (CUORE) is the first bolometric experiment searching for 0νββ decay that has been able to reach the one-tonne mass scale. The detector, located at the LNGS in Italy, consists of an array of 988 TeO2 crystals arranged in a compact cylindrical structure of 19 towers. CUORE began its first physics data run in 2017 at a base temperature of about 10 mK and in April 2021 released its 3rd result of the search for 0νββ, corresponding to a tonne-year of TeO2 exposure. This is the largest amount of data ever acquired with a solid state detector and the most sensitive measurement of 0νββ decay in 130Te ever conducted, with a median exclusion sensitivity of 2.8×10^25 yr. We find no evidence of 0νββ decay and set a lower bound of 2.2 ×10^25 yr at a 90% credibility interval on the 130Te half-life for this process. In this talk, we present the current status of CUORE search for 0νββ with the updated statistics of one tonne-yr. We finally give an update of the CUORE background model and the measurement of the 130Te 2νββ decay half-life, study performed using an exposure of 300.7 kg⋅yr.

Speaker: Dr Mattia Beretta (UC Berkeley)

CUORE_DISCRETE_2022.pdf

5:00 PM → 5:30 PM Quark Flavour¶

Convener: Session Chair: Marco Fedele (KIT, TTP)

5:00 PM Study of New Physics in Bq0−B¯q0 Mixing:Challenges, Prospects and Implications for Leptonic Decays¶

The phenomenon of $B_q^0-{\overline{B}}_q^0$ mixing $(q=d,s)$ provides a sensitive probe for physics beyond the Standard Model. We have a careful look at the analyses of the determination of the Unitarity Triangle apex, which is needed for the Standard Model predictions of the $B_q$ mixing parameters, and we explore how much space for New Physics is left through the current data. We study the impact of tensions between inclusive and exclusive determinations of the CKM matrix elements $|V_{ub}|$ and $|V_{cb}|$ and we focus on the $\gamma$ angle extraction. We present various future scenarios and we discuss the application of these results for leptonic rare $B$ decays, which allows us to minimise the CKM parameters impact in the New Physics searches. Performing future projections, we explore and illustrate the impact of increased precision on the key input measurements. It will be exciting to see how more precise data in the future high-precision era of flavour physics can lead to a much sharper picture.

Speaker: Eleftheria Malami (Siegen University)

talk_DISCRETE22.pdf

5:15 PM B mesons lifetimes within the HQE¶

The heavy quark expansion (HQE) provides a well established framework to compute inclusive decay widths of heavy hadrons in terms of a systematic expansion in inverse powers of the constituent heavy quark mass. By including for the first time the contribution of the Darwin operator, SU(3)${}_F$ breaking corrections to the matrix element of dimension-six four-quark operators and the so-called eye-contractions, we update the SM predictions, based on the HQE, of the total widths of the $B^{+}$, $B_d$, and $B_s$ mesons, as well as of the lifetime ratios $\tau (B^{+})/\tau (B_d)$ and $\tau (B_s)/\tau (B_d)$. Overall we find very good agreement with the corresponding experimental determinations, however, the prediction of $\tau (B_s)/\tau (B_d)$ is particularly sensitive to the value of the Darwin parameter and of the size of SU(3)${}_F$ breaking in the non-perturbative input, which are so far still poorly constrained, leading to some tension in specific scenarios.

Speaker: Maria Laura Piscopo (University of Siegen)

Talk-Discrete.pdf

Thu, November 10 ¶

9:00 AM → 10:30 AM Plenary¶

Convener: Session Chair: Chara Kitsaki

welcome_talk_un.pdf

9:30 AM Tests of discrete symmetries at low energies¶

Permanent electric dipole moments probe the joint violation of parity and time-reversal symmetries, collecting many potential sources into a single low-energy observable. Although the Standard Model predicts finite values in many systems, these are too small for present-day experiments to detect.

Experimental results consistent with zero are thus interpreted, via the CPT theorem, as constraining the new sources of CP-violation required to generate the cosmological baryon asymmetry. Complementary results from many different experiments are needed to jointly constrain high-energy CP-violation, using global analysis to confront the multi-scale problem of interpreting low-energy experimental data.

I will discuss the experimental status today, focusing especially on precision measurements using neutrons and diamagnetic atoms. New technological developments, prospects for improved measurements, and connections to other observables will be mentioned.

Speaker: Skyler Degenkolb (Universität Heidelberg)

SMD_DISCRETE2022_20221110.pdf

10:00 AM New avenues in dark matter detection¶

The exploration of dark matter beyond the WIMP is of vital importance towards resolving the identity of dark matter. I will present new proposals for the direct detection of light dark matter which hold much promise. These include the use of superconducting nanowires, two-dimensional targets such as graphene, and heavy fermion systems. Considering dark matter interactions with these targets, I will demonstrate the potential of the light dark matter direct detection program in upcoming years.

Speaker: Yonit Hochberg

YH_Discrete_2022.pdf

10:30 AM → 11:10 AM Coffee break¶

11:10 AM → 12:10 PM Plenary¶

Convener: Session Chair: Maria Laura Piscopo (University of Siegen)

welcome_talk_un.pdf

11:10 AM Flavor Probes of Axion Dark Matter¶

Standard Model extensions with light axions are well-motivated by the observed Dark Matter abundance and the Peccei-Quinn solution to the Strong CP Problem. In general such axions can have large flavor-violating couplings to SM fermions, which naturally arise in scenarios where the Peccei-Quinn symmetry also explains the hierarchical pattern of fermion masses and mixings. I will discuss how these couplings allow for efficient axion production from the decays of SM particles, giving the opportunity to probe flavored axion Dark Matter with precision flavor experiments, astrophysics and cosmology.

Speaker: Robert Ziegler

Ziegler.pdf

11:40 AM Axions in the early universe¶

Scattering and decay processes of thermal bath particles in
the early universe can dump relativistic axions in the primordial plasma. If
produced with a significant abundance, their presence can leave observable
signatures in cosmological observables probing both the early and the late
universe. In this talk, I will focus on the QCD axion and I will present recent and
significant improvements for the calculation of the axion production rate across the
different energy scales during the expansion of the universe. I will apply these
rates to predict the abundance of produced axions, and I will present the latest
cosmological bounds on the axion mass and couplings.

Speaker: Francesco D'Eramo (University of Padua & INFN Padua)

04_DEramo_DISCRETE2022.pdf

12:10 PM → 1:15 PM Lunch break¶

1:15 PM → 1:45 PM Coffee break¶

1:45 PM → 6:00 PM Free afternoon¶

6:00 PM → 9:00 PM Conference dinner¶

Fri, November 11 ¶

9:30 AM → 10:30 AM Plenary¶

Convener: Session Chair: Marcel Hohmann (University of Melbourne)

welcome_talk_un.pdf

9:30 AM Dark Matter from Exponential Growth: Pandemic Dark Matter¶

We propose a novel mechanism for the production of dark matter (DM) from a thermal bath, based on the idea that DM particles $\chi$ can transform heat bath particles $\psi$: $\chi \psi \to \chi \chi$. For a small initial abundance of $\chi$ this leads to an exponential growth of the DM number density. We demonstrate that this mechanism complements freeze-in and freeze-out production in a generic way, enabling new possibilities to explain the observed DM abundance. After this general discussion we comment on connections to discrete symmetries and consider possible model realizations as well as observational prospects. In particular for sterile neutrinos we show that an exponential production regime naturally occurs for self-interacting sterile neutrinos, which opens up significant parameter space for sterile neutrino DM in a very simple model.

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

Depta_DISCRETE22.pdf

10:00 AM Looking into the heart of darkness - two-phase xenon time projection chambers for direct dark matter searches¶

The fundamental nature of dark or invisible matter remains
one of the great mysteries of our time. A leading hypothesis is that dark matter is
made of new elementary particles, with proposed masses and interaction cross
sections spanning an enormous range. Amongst the technologies developed to
search for dark matter particles, two-phase (liquid and gas) xenon time projection
chambers are currently leading the field, providing unprecedented sensitivities and
a large discovery potential. I will briefly present the development of these detectors
from their earliest stages, then show first results from multi-tonne detectors
currently taking data deep underground. I will also discuss the ongoing the R&D;
towards the next-generation DARWIN experiment.

Speaker: Laura Baudis (University of Zurich)

baudis_discrete2022.pdf

10:30 AM → 11:10 AM Coffee break¶

11:10 AM → 12:10 PM Plenary¶

Convener: Session Chair: Syuhei Iguro

welcome_talk_un.pdf

11:10 AM Present status of neutrino physics from a theory perspective¶

One of the most important achievements in the field of particle physics was the discovery of neutrino oscillations. This implies the massive nature of neutrinos and in turn points to the existence of physics Beyond the Standard Model. In this talk I will chiefly focus on several strategies to probe new physics with neutrinos. First and foremost, I will discuss some classes of neutrino mass models and the respective detection prospects. I will also elaborate on the strategies to
probe various new physics that is unrelated to neutrino mass, e.g. axion-like particles, at near-future neutrino experiments such as DUNE. Finally, I will discuss anomalies, in particular the excess of events at LSND and MiniBooNE experiments and respective BSM explanations.

Speaker: Vedran Brdar (CERN)

Vedran.pdf

11:40 AM Search for CP violation in neutrino oscillations in standard and non-standard physics scenarios¶

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Speaker: Julia Gehrlein (Brookhaven National Laboratory)

gehrlein_cpv.pdf

12:10 PM → 2:00 PM Lunch break¶

2:00 PM → 3:00 PM Plenary¶

Convener: Session Chair: Margarida (Gui) Rebelo

welcome_talk_un.pdf

2:00 PM Probes of Axion Dark Matter¶

This talk will give an overview over axions as dark matter and ways to detect them.

Speaker: Prof. Joerg Jaeckel (Heidelberg Univ.)

2:30 PM (Anti-)hydrogen spectroscopy for tests of CPT and Lorentz invariance¶

Cold antihydrogen, the bound state of an antiproton and a positron, is an ideal laboratory to test the fundamental CPT symmetry, one of the cornerstones of the Standard Model (SM) of particle physics, by comparing its energy levels to ordinary hydrogen. Hydrogen is one of the best studied atoms experimentally, the two best-known transitions being the 1S-2S two-photon transition and the ground-state hyperfine transition. The ALPHA collaboration at CERN-AD has obtained first experimental results for both transitions in a Penning trap, and ASACUSA is preparing a measurement using a beam. As CPT is strictly conserved in the SM, its observation would immediately point to new physics, e.g., originating from string theory where the CPT theorem is not necessarily valid, or other reasons like decoherence. No theoretical framework exists that predicts CPT violation, but the Standard Model Extension (SME) is a phenomenological model useful to classify and compare measurements of different properties of matter and antimatter. As the SME is based on Lorentz invariance violation, it can be tested by experiments with matter only. E.g., using a beam of cold hydrogen atoms initially built to characterize the in-beam method, ASACUSA has performed experiments on the orientation dependence of an external static magnetic field for hydrogen hyperfine measurements, and preparations are under way to study the hyperfine structure of deuterium. An overview will be given on the current and planned experiments and their implications on the search for CPT violation.

Speaker: Eberhard Widmann

06_Widmann DISCRETE22.pdf

3:00 PM → 3:15 PM Plenary: DISCRETE 2024¶

Convener: Session Chair: Margarida (Gui) Rebelo

welcome_talk_un.pdf

3:00 PM DISCRETE 2024¶

Presentation of DISCRETE 2024 in Ljubljana.

Speaker: Miha Nemevšek

07_mnrClosureDiscrete22.pdf

Discrete2024.pdf

3:15 PM → 4:00 PM Coffee break: Farewell coffee¶