Standard Model CP Violation and Baryogenesis

Pal, Pratyay (2025) Standard Model CP Violation and Baryogenesis. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Pratyay Pal (20MS051)) 20MS051_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (1MB)

Abstract

We first analyze the necessity of the assumption that universe today must be Baryon asymmetric to describe the observations. Next we show what would be the requirements to create such a baryon asymmetry - These are the three famous Sakharov’s Conditions. We test this conditions with respect to the minimal standard model of SU(3)C N SU(2)L N U(1)Y . Initially it seems like all three conditions can be made to satisfy within the minimal standard model (SM). Hence we try to calculate the produced amount of baryon asymmetry within Standard Model via Electroweak Baryogenesis (EWBG) mechanism. This, as it turns out, gives us an amount of baryon asymmetry too small as compared to today’s observed value. We list down the possible problems that SM has in regards to explaining this number - they are mainly the absence of enough Charge-Parity (CP) violation in the single Cabibo-Kobayashi-Maskawa (CKM) phase and the fact that the scalar field coupling for the observed Higgs mass is not sufficient to drive a strong first order phase transition. Finally we look for an alternative solution in the form of Two Higgs Doublet Model (2HDM) - we take a Type-II 2HDM with an explicit CP violating phase in the mixed mass term. We keep the second Higgs at a very high mass scale as to avoid possible collider implications. Finally we repeat the calculations pertaining to the EWBG mechanism and search the parameter space where successful baryogenesis may occur.

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