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.
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.
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.
19.11.2024
Tomasz Krajewski
Nicolaus Copernicus Astronomical Center, Warsaw