PhD Thesis - Topics in SUSY Phenomenology at the LHC

Abstract

This dissertation focuses on phenomenological studies for possible signals for supersymmetric events at the Large Hadron Collider (LHC). We have divided our endeavours into three separate projects. First, we consider SUSY models where the gluino production at the LHC should be rich in top and bottom quark jets. Requiring $b$-jets in addition to missing energy $\eslt$ should, therefore, enhance the supersymmetry signal relative to Standard Model backgrounds. We quantify the increase in the supersymmetry reach of the LHC from $b$-tagging in a variety of well-motivated models of supersymmetry. We also explore $top$-tagging at the LHC. Second, we explore the prospects for detecting the direct production of third generation squarks in models with an inverted squark mass hierarchy. This is signalled by $b$-jets + $\eslt$ events harder than in the Standard Model, but softer than those from the production of gluinos and heavier squarks. We find that these events can be readily separated from SM background (for third generation squark masses in the 200-400 GeV range), and the contamination from the much heavier gluinos and squarks although formidable can effectively be suppressed. Third, we attempt to extract model-independent information about neutralino properties from LHC data. assuming only the particle content of the MSSM and that all two-body neutralino decays are kinematically suppressed, with the neutralino inclusive production yielding a sufficient cross section. We show that the Lorentz invariant dilepton mass distribution encodes clear information about the relative sign of the mass eigenvalues of the parent and daughter neutralinos. We show that we can extract most neutralino mass matrix parameters if there is a double mass edge.