Beyond standard model collider phenomenology of Higgs physics and supersymmetry

Abstract

In this thesis I study the collider phenomenology of BSM physics at the LHC, concentrating on the Higgs boson and supersymmetery. The implications and effects on cross sections of the loss of unitarity in scattering processes involving multiple vector bosons and/or the Higgs, when the Higgs couplings to the W and the Z are non-SM, is studied using an effective Lagrangian. Subsequently methods to remove unwanted background from transversely polarised vector bosons are explored, which enable an estimation of the potential to measure the Higgs couplings to weak bosons in a model-independent way via vector boson fusion. MSSM effects on Higgs production and decay are also considered, concentrating on the effects due to light stops, sbottoms and staus. Amongst other things, we find that light 3rd generation squarks generally produce asymmetrical alteration in signal strengths of different production channels, generally causing µ_{V BF} / µ_ggF > 1. Finally we extend some ATLAS analyses in the low Δm = m^-_t − m^-0/χ₁ region, extending the excluded masses of light stops. This enables us to limit the maximum effects of light stops on the Higgs, and further limits the parameter space where the light stop scenario of electroweak baryogenesis is viable.

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Identifiers

ORCID for Alexander Belyaev: orcid.org/0000-0002-1733-4408

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