Higgs Physics in Supersymmetric Models

Abstract

Standard Model (SM) successfully describes the particle spectrum in nature and the interaction between between these particles using gauge symmetries. However, in order to give masses to these particles, the electroweak gauge symmetry must be broken. In the SM, this is achieved through the Higgs mechanism where a scalar Higgs field acquires a vacuum expectation value. It is well known that the presence of a scalar field in the SM leads to a hierarchy problem, and therefore the SM by itself can not be the fundamental theory of nature. A well-motivated extension of the SM which addresses this problem is the Minimal Supersymmetric Standard Model (MSSM). The Higgs sector in the MSSM has a rich phenomenology and its predictions can be tested at colliders. In this thesis, I will describe three examples in supersymmetric models where the Higgs phenomenology is significantly different from that in SM. The first example is the MSSM with large tan Β where the Higgs coupling to the bottom quarks receives large radiative supersymmetric QCD corrections. As a consequence, Higgs production in association with bottom quark can be a dominant Higgs production mode in certain parameter spaces of the MSSM. A second example is an extension of the MSSM wherein a fourth generation of chiral fermions and their super-partners are added. I will show that the Higgs boson in such models can be as heavy as ~ 500 GeV. Finally, as a third example, the MSSM with one of the stops lighter than the top quark is considered. Such a scenario is required to generate sufficient baryon asymmetry in the universe through the process of electroweak baryogenesis. By using the correlations between the Higgs production and decay rates, it will be shown that the electroweak baryogenesis in the MSSM is highly constrained.