2021/2022 - WINTER SEMESTER
25.01.2022
Wojciech Kotlarski
NCBJ, Warsaw
The history and present status of an R-symmetric SUSY
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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.
11.01.2022
Lorenzo Ubaldi
SISSA/INFN/IFPU, 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.
Slides
14.12.2021
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.
30.11.2021
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.
Slides
23.11.2021
Atri Bhattacharya
University of Liège
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.
Slides
16.11.2021
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 \nu 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.
Slides
09.11.2021
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.
26.10.2021
Mohammad Altakach
University of Warsaw
Testing BSM models with global comparisons to collider measurements: An illustrative example
Despite the fact that no signals of new physics have been found in the first two runs of the LHC at CERN, there are still high hopes that new particles will show up in the future high-luminosity runs. It is also clear that such signals will likely appear as small deviations from the the Standard Model (SM) predictions and that they will critically depend on the size of the theory uncertainties which makes precision predictions of both the SM background and the new physics signals an essential ingredient for a correct and reliable comparison between experimental data and theories describing the fundamental interactions of Nature. In this talk I discuss a new calculation of electroweak (EW) top-pair hadroproduction in extensions of the SM with extra heavy neutral and charged spin-1 resonances. Then I describe the Contour method which allows us to set limits on beyond the SM (BSM) theories. Finally, I explain how we use our calculation within Contour in order to set limits on models with additional heavy gauge bosons using LHC measurements, and illustrate this with an example using the leptophobic Topcolour (TC) model.
Slides
19.10.2021
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.
Slides
05.10.2021
Krzysztof Jodłowski
NCBJ, Warsaw
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.