SEMESTER 2024/25 - WINTER
08.10.2024
Krzysztof Jodłowski
Institute for Basic Science, Daejeon
Clockwork inspired extra dimension models at future lepton colliders, beam dumps, and SN1987
Generalized Continuum Clockwork (GCC) is an extra-dimensional generalization of the clockwork mechanism dynamically generating hierarchical couplings and mass scales. We study three benchmark geometries of GCC: the Randall-Sundrum (RS) model with a warped extra dimension, linear dilaton background, and a generalized linear dilaton model with a novel Kaluza-Klein (KK) graviton structure. We investigate the prospects of searching for signatures of CCW models at current and future colliders like the LHC, CLIC, and FCC-ee using visible decays of KK gravitons and the radion. We also explore the long-lived regime of these states at beam dump experiments like Belle II, FASER2, MATHUSLA, and SHiP, as well as constraints from astrophysical and cosmological observations. We find that combining both kind of searches will enable comprehensive coverage of the relevant CCW parameter space. Finally, we update the prospects of the RS with a third, dark brane, which was proposed as a potential origin of the NANOGrav gravitational wave signal from a first-order phase transition.
Slides
22.10.2024
Marco Merchand
KTH Stockholm
Probing Strong Dynamics and Phase Transitions: Gravitational Wave Signatures in a Maximally Symmetric Composite Higgs Model
In this work we explore a maximally symmetric composite Higgs model featuring a next-to-minimal coset structure, where a pseudoscalar singlet arises alongside the Higgs doublet. Maximal symmetry ensures a finite radiative scalar potential, allowing for a detailed study of electroweak phase transitions in the presence of explicit CP violation. We explore the implications of a CP-violating source in the strong sector, which induces a Z2-asymmetric scalar potential and leads to a non-zero vacuum expectation value for the singlet. After incorporating finite temperature corrections and imposing constraints from current LHC bounds and electric dipole moment measurements, we find that the explicit CP violation drives a strong first-order phase transition. We illustrate that these phase transitions produce gravitational wave signatures that could be observable at future detectors, offering a novel approach to probing composite Higgs models beyond collider experiments. This work highlights the potential of gravitational waves as complementary probes of the strong dynamics in new physics scenarios.
Slides
05.11.2024
Peter Matak
Comenius University, Bratislava
Feynman rules for the Boltzmann equation
In the first part of the seminar, we focus on unitarity and optical theorem and their relation to quantum kinetic theory. Using the holomorphic modification of cutting rules, we demonstrate that even when starting with zero-temperature Feynman rules and classical phase-space densities, thermal mass and quantum statistical effects inconspicuously enter the Boltzmann equation. The second part will then focus on calculating reaction rate CP asymmetries necessary to source the matter-antimatter asymmetry according to Sakharov's conditions. It will be shown how the direct use of unitarity allows for tracking the asymmetry cancellations in a purely diagrammatic way.
Slides
12.11.2024
Priyanka Lamba
Università di Bologna
Quantum properties of H->VV: precise predictions in the SM and sensitivity to new physics
The CMS and ATLAS experiments have recently confirmed spin entanglement in top-antitop pairs at high-energy colliders, inspiring further exploration of other processes. This talk addresses the sensitivity of quantum observables in the H->VV process. We study Higgs boson decays into vector bosons in four-lepton final states, calculating quantum observables within the Standard Model up to next-to-leading order (NLO) in electroweak couplings. Our results show that NLO corrections significantly modify quantum correlation patterns relative to tree-level predictions. Additionally, we analyze the effects of potential new physics in both Higgs couplings to four leptons and modifications to the H->VV vertex on quantum observables.
Slides
03.12.2024
Tomasz Krajewski
Nicolaus Copernicus Astronomical Center, Warsaw
How to calculate the terminal velocity of a bubble wall?
Cosmological first order phase transitions are intriguing processes with rich phenomenological consequences. They proceed via nucleation of bubbles containing energetically favorable phase in the background of the metastable phase. Such bubbles expand due release of the latent heat, but can be slowed down and even reach the constant subliminal velocity by interactions with the plasma of (not necessarily Standard Model) particles. The terminal velocity determines phenomenological consequences of the transition, since faster walls emit stronger gravitational waves, while slower walls are expected to produce the higher matter-antimatter asymmetry in scenarios of the electroweak baryogenesis, but is much harder to predict than other parameters of the transition. Even though, a significant effort has been undertaken by the community to calculate the velocity from first principles, the final conclusion was still not clear. The recent progress in this field, both numerical and analytical, will be reported in this talk.
07.01.2025
Maxim Laletin
University of Warsaw
21.01.2025
Mark Goodsell
LPTHE, Paris