Faculty of Physics University of Warsaw > Events > Seminars > "High Energy, Cosmology and Astro-particle Physics (HECA)" Seminar

"High Energy, Cosmology and Astro-particle Physics (HECA)" Seminar

2020/2021 | 2021/2022 | 2022/2023 | 2023/2024 | 2024/2025 | Seminar homepage

join us at 11:15

Ayuki Kamada (University of Warsaw)

Maximally self-interacting dark matter

Self-interacting dark matter (SIDM) has been attracting growing interest, since it may solve tensions between naive cold dark matter (CDM) predictions and the observed small-scale structure of the Universe. Observations of dark-matter halos in a wide range of masses, from Milky Way’s dwarf spheroidal galaxies to galaxy clusters, may indicate that the SIDM cross section strongly depends on the velocity. We demonstrate that the indicated velocity dependence is generically realized when the self-scattering saturates the partial-wave Unitarity bound. Saturating the partial-wave Unitarity bound pins down the mass of dark matter as well as the underlying model parameter.More specifically, we consider the gauged Lmu-Ltau model and composite asymmetric dark matter model, and discuss implications for cosmology like the H0 tension and dark matter direct-detection experiments.

https://us02web.zoom.us/j/85478248551

join us at 11:15

Hidetoshi Otono (Kyushu University)

Status of the FASER experiment

The FASER experiment is a new small and inexpensive experiment that is being placed 480 meters downstream of the ATLAS experiment at the CERN LHC. FASER is designed to discover dark photons and other light and very weakly-interacting particles that are produced in the far-forward region, outside of the ATLAS detector acceptance. FASER would also directly detect collider neutrinos for the first time and study their cross sections at TeV energies, where no such measurements currently exist. The experiment has been successfully constructed and installed and will take data during Run-3 of the LHC. This talk will present the physics prospects, detector design, and commissioning status of FASER.

https://us02web.zoom.us/j/85478248551

join us at 14:00

Jan Heisig (Louvain University, CP3 and RWTH Aachen)

Bound state effects on dark matter coannihilation - pushing the boundaries of minimal dark sectors

Note unusual time!!!

Bound-state formation effects can have a large impact on the dynamics of dark matter freeze-out in the early Universe, in particular, for colored coannihilators. We present a general formalism to include an arbitrary number of excitations of bound states in terms of an effective annihilation cross section. For a coannihilator in the fundamental representation of SU(3)c, we discuss radiative bound-state formation, decay, and electromagnetic transition rates among them. We then assess the impact of bound states within a minimal dark sector containing a Majorana dark matter candidate and a colored scalar t-channel mediator. We consider the well-known coannihilation regime as well as the regime of conversion-driven freeze-out (or coscattering), where the relic abundance is set by the freeze-out of conversion processes. We find that the latter is considerably enhanced into the multi-TeV region due to bound-state effects. This has far-reaching implications for the search strategies at the upcoming LHC runs as conversion-driven freeze-out predicts a long-lived coannihilator. We also comment on the role of bound-state effects in scenarios of non-thermalized dark matter, i.e. freeze-in or superWIMP production.

https://us02web.zoom.us/j/85478248551

join us at 11:15

Zhi-Wei Wang (Lund University)

Dark Phase Transition and Gravitational Wave of Strongly Coupled Hidden Sectors

We go beyond the state-of-the-art by combining first principal lattice results and effective field theory approaches as Polyakov Loop model to explore the non-perturbative dark deconfinement-confinement phase transition and the generation of gravitational-waves in a dark Yang-Mills theory. We further include fermions with different representations in the dark sector. Employing the Polyakov-Nambu-Jona-Lasinio (PNJL) model, we discover that the relevant gravitational wave signatures are highly dependent on the various representations. We also find a remarkable interplay between the deconfinement-confinement and chiral phase transitions. In both scenarios, the future Big Bang Observer experiment has a higher chance to detect the gravitational wave signals.

https://us02web.zoom.us/j/85478248551

join us at 11:15

Heejung Kim (IBS, Daejeon, CTPU and KAIST, Taejon)

Manifesting the self-heating dynamics of a sub-component dark matter in astrophysical/cosmological observations

Scenarios of non-minimal dark matter (DM) contents and interactions inside a dark sector have drawn considerable attention, partially because of their abilities to resolve various phenomenological issues and provide extra power to many current/future experiments of searching for their signals in new and creative ways. In this talk, by taking a two-component DM scenario as an example, we demonstrate that multi-component DM scenarios can exhibit unique cosmological dynamics called 'self-heating'. During the self-heating epoch, a strongly self-interacting sub-component DM dynamically develops higher temperature than the SM one. We discuss the possible cosmological/astrophysical imprints from the temperature enhancement. Notably, we demonstrate that the warm DM constraints can be complementary to missing-energy/momentum experiments while providing additional information about the multi-component feature of DM.

Reference: arXiv:2111.06808 (hep-ph)

https://us02web.zoom.us/j/85478248551

join us at 11:15

Juri Smirnov (Oskar Klein Centre for Cosmo Particle Physics, Stockholm University)

Thermal Squeezeout of Dark Matter

I will discuss a detailed study of the confinement phase transition in a dark sector with a SU(N) gauge group and a single generation of dark heavy quark. We focus on heavy enough quarks such that their abundance freezes out before the phase transition and the phase transition is of first-order. We find that during this phase transition the quarks are trapped inside contracting pockets of the deconfined phase and are compressed enough to interact at a significant rate, giving rise to a second stage of annihilation that can dramatically change the resulting dark matter abundance. As a result, the dark matter can be heavier than the often-quoted unitarity bound of ~ 100 TeV. Finally I will show a concrete example where the link between the dark sector and the standard model is facilitated by a simple Z’ model.

https://us02web.zoom.us/j/85478248551

join us at 11:15

Wojciech Kotlarski (NCBJ, Warsaw)

The history and present status of an R-symmetric SUSY

In 2007 Kribs, Poppitz and Weiner proposed a new solution to the supersymmetric flavour problem, without flavour-blind mediation. The solution was based on a preserved at the EW scale continuous (or sufficiently larger than the matter parity) R-symmetry. In this talk I will review the long line of research on the Minimal R-symmetric Supersymmeric Standard Model - starting from the original motivation, via the analysis of its Higgs sector, dark matter, collider constraints and finally back to the lepton flavour violation and muon anomalous magnetic moment.

https://us02web.zoom.us/j/85478248551

join us at 11:15

Lorenzo Ubaldi (SISSA and INFN, Trieste)

Dark photon dark matter from a rolling inflaton

A scalar inflaton coupled to a dark photon can produce a large density of the latter. I will discuss the mechanism underlying this production, which takes place mostly at the end of inflation. After reheating, the dark photons are relativistic at first and then redshift to non relativistic. Their energy density today can match that of the observed dark matter in a wide region of parameters of the model. It is interesting to study in detail also the dark photon power spectrum and its cosmic evolution, which predicts a clumpy nature of this dark matter candidate, possibly useful for experimental searches.

https://us02web.zoom.us/j/85478248551

join us at 11:15

Fotis Koutroulis (University of Warsaw)

On RG Flows near a UV and Quantum, 1st Order Phase Transition - A Profile of a Higgs Mechanism

In this work I will describe the construction of the zero temperature (no compact dimensions) effective action for an SU(2) Yang–Mills theory in five dimensions, with boundary conditions that reduce the symmetry on the four-dimensional boundary located at the origin to a U(1)-complex scalar system. In order to be sensitive to the Higgs phase, we need to include higher dimensional operators in the effective action, which can be naturally achieved by generating it by expanding the corresponding lattice construction in small lattice spacing, taking the naive continuum limit and then renormalizing. In addition, we build in the effective action non-perturbative information, related to a first order quantum phase transition known to exist. As a result, the effective action acquires a finite cut-off that is low and the fine tuning of the scalar mass is rather mild.

https://us02web.zoom.us/j/85478248551

join us at 11:15

Mariana Carrillo González (Imperial College, London)

Analyzing the Cosmology and Signals of Pseudo-Dirac Dark Matter

Strong bounds from CMB observations have pushed us away from the standard WIMP picture of dark matter (DM). Nevertheless, a dark matter candidate of thermal origin does not require elastic weak interactions to lead to the observed DM abundance. In fact, the simple appearance of Majorana masses changes the standard picture of WIMP DM. In this talk, I will present a careful analysis of the cosmological evolution and experimental signals for pseudo-Dirac DM. I will focus on the importance of computing the DM abundance to understand the DM signals and on the complementarity of different searches.

https://us02web.zoom.us/j/85478248551

join us at 11:15

Atri Bhattacharya (University of Liege)

Investigating Super-Heavy Dark Matter decays from Earth at IceCube

Recent theoretical work has explored dark matter accumulation in the Earth and its drift towards the center of the Earth that, for the current age of the Earth, does not necessarily result in a concentration of dark matter in the Earth's core. We consider a scenario of long-lived, super heavy dark matter that is either uniformly distributed throughout the earth or mirrors earth's rock profile, and that decays to tau or muon neutrinos. We explore the potential of a large volume neutrino telescope such as IceCube to detect or constrain signatures of such non-trivial dark matter distributions over a period of 10 years.

https://us02web.zoom.us/j/85478248551

join us at 11:15

Priyanka Lamba (University of Warsaw)

Aspects of Heavy Supersymmetry

The discovery of the Higgs boson raises the question of its "lightness" in mass when the Standard Model is considered as an effective quantum field theory. Supersymmetry is the only currently known symmetry which can protect the Higgs mass while still treating the Higgs as an elementary quantum field. However in the view of null experimental confirmation from both direct (LHC) and indirect searches (flavour, dark matter) of the supersymmetric particles and the constraints from the Higgs mass, several possible heavy spectra for supersymmetric partners have been proposed.

In first part of my talk, I will discuss the possible origins of these heavy spectra by considering a many sequestered spurion fields as carriers of supersymmetry breaking. We show that "natural" supersymmetric spectrum is possible in these models and in particular a "coherent" scenario leads to low fine tuning, light Higgsino mixed dark matter (a la focus point region) even with heavy supersymmetric spectrum. We then consider this model within the context of string landscape, where we use the Bousso-Polchinski framework of four form fluxes to model the spurions. We show that the flavour violating parameters of supersymmetric spectrum can be "diluted" away in the presence of large number of fluxes.

In other part of my talk, I will discuss one of the possible supersymmetric spectra which emerges by considering all the data is the generation split (Gensplit) spectrum which allows for flavour violation to be present for the first two generations, which are heavy. We study this spectrum within the context of supersymmetric SU(5) and proton decay. The results are quite interesting and dependent on the proton decay mode considered. The strongest bound p to k u is now modified depending on the flavour of the neutrino and brings the parameter space within the realms of upcoming experiments of JUNO, HYper-K, and DUNE.

https://us02web.zoom.us/j/85478248551

join us at 11:15

Keri Vos (Maastricht University)

B mesons as a Telescope for New Physics

B meson decays are important players in the search for physics beyond the Standard Model (SM) of particle physics. Linked to the antimatter-matter asymmetry in the universe, a key interest in this is also improving the understanding of the mechanism of CP violation within the SM. The large amount of data gathered by the B factories and LHCb allows testing the SM with an unprecedented precision, probing scales much higher than the reach of direct searches at the LHC. Naturally, this also requires precise theoretical predictions. In this talk, I will present some of the challenges and new ideas to push the theoretical precision up. Specifically, I will focus on the determination of the CKM element Vcb, non-leptonic decays and Lepton Flavor Violation in baryon decays.

https://us02web.zoom.us/j/85478248551

join us at 11:15

Antonio Enea Romano (UDEA & UW &CERN)

The momentum effective sound speed (MESS) and dualities of cosmological pertubations

The same spectrum of curvature perturbations can be explained by many different models. We first show this degeneracy by introducing homospectral expansion histories, i.e. classes of different expansion histories producing the same spectrum. We then consider other types of degeneracy associated to systems having the same momentum effective sound speed (MESS) of comoving curvature cosmological perturbations, which can be used to perform model independent analysis of observational data, or to define effective theories for different systems such as mutifields, modified gravity or super-gravity. As an application we show how the MESS can be used to obtain single field effective theories for some multifields inflationary models, and how it can be useful to compare different systems in terms of a unifying approach.

https://us02web.zoom.us/j/85478248551

room B2.38, Pasteura 5 at 11:15

Krzysztof Jodłowski (Narodowe Centrum Badań Jądrowych)

Indirect detection of long-lived particles in a less-simplified scenario

Simplified models of light new physics constitute an important benchmark for future experimental programs that require further dedicated theoretical efforts. It is understood that realistic such scenarios will likely involve other degrees of freedom, including heavy particles, which can introduce additional modes of detection. In this talk, we will focus on an example of such model, in which the dark sector couples to the SM via a popular light dark Higgs portal, while it also contains a secluded scalar dark matter (DM) candidate with mass above the TeV scale. We will illustrate interesting phenomenological features of such scenario that allow one to avoid stringent cosmological bounds, while at the same time lead to complementary probes in intensity frontier searches for light new physics, DM indirect detection (ID), and cosmic microwave background radiation surveys. We will also highlight possible non-local effects present in DM ID that could significantly affect relevant detection strategies for such models via, e.g., i) an additional contribution to the flux coming from the “diffusion from GC” effect, ii) linear fall-off in the long lifetime regime due to finite support of the dark matter density.
https://us02web.zoom.us/j/85478248551