Testing the Standard Model with LHC Physics and signals from Cosmological Phase Transitions.

• Grant number: 24/03583-1
• Support Opportunities: Scholarships in Brazil - Master
• Start date: September 01, 2024
• End date: February 28, 2026
• Field of knowledge: Physical Sciences and Mathematics - Physics - Elementary Particle Physics and Fields
• Principal Investigator: Gustavo Alberto Burdman
• Grantee: Marvin Mascioli Janini
• Host Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 19/04837-9 - Particle Physics Phenomenology, AP.TEM

Abstract

The Standard Model (SM) of Particle Physics successfully describes the interactions of all currently known elementary particles. In particular, with the discovery of the Higgs boson in 2012, the spectrum of the SM was completed. The Higgs sector and its interactions are being tested at the Large Hadron Collider (LHC) with increasing precision. However, these tests have not yet reached the precision with which the gauge interactions of fermions have been tested over the past thirty years. Precision tests of the Higgs sector of the SM will be the frontier of particle physics in the coming years, particularly in the era of high luminosity at the High Luminosity LHC (HL-LHC). Given that the energy of the HL-LHC will be practically the same as that of the LHC, the new frontier will not be of new energies, but rather of greater precision.From a theoretical point of view, there are many reasons to expect deviations in the Higgs sector regarding the predictions of the SM. To begin with, the Higgs sector is included in the SM as a way to solve the problem of the incompatibility of gauge invariance with the masses of fermions and gauge bosons. The Higgs mechanism implies the existence of a potential where the electroweak scale is introduced ad hoc. In fact, in the entire theory, there is only one term with a mass scale, and it is the quadratic term in the Higgs field in the potential. The origin of the electroweak scale is thus one of the central questions in particle physics today. Furthermore, the electroweak scale appears unstable under radiative corrections (hierarchy problem). Among other problems of the SM, we have the origin of neutrino masses, which requires either a particle outside the SM (right-handed neutrino) or a mechanism at energies above the electroweak scale (see saw); the origin of dark matter in the universe, and the origin of the baryon-antibaryon asymmetry.Extensions of the SM are proposed to try to explain these issues. This project has two main aspects: 1) To study extensions of the SM that modify the couplings of the Higgs boson with gauge bosons, fermions, and even with itself. The extensions in question result in dependence of the Higgs couplings on momentum. These models should be studied with special attention to signals at the HL-LHC. 2) To study the effects of extensions of the SM on the Higgs sector in cosmological phase transitions. The spontaneous breaking of electroweak symmetry implies the existence of a phase transition in the cosmological history of the universe, at a given critical temperature. This phase transition has been widely studied. However, in many extensions of the SM, and particularly in those where the Higgs is a (pseudo) Nambu-Goldstone boson (pNGB), there should be other phase transitions. We propose to study the details of these phase transitions and their possible correlations with experimental signals, both at the LHC and in experiments detecting gravitational waves.