Standard Model Gauge Coupling Unification and Vacuum Stability with Vector-like Particles

Abstract

Unification of the three Standard Model (SM) gauge couplings at the scale from5.5×1015 GeVto2.4×1018 GeV(reducedPlanckscale)hasbeenachieved in the models where the matter part of SM is extended by postulating the existence of new vector-like particles. The new vector-like particles carry the same quantum numbers as the SM particles do and so they are called as the standard vector-like particles. Masses of these particles are of the order of 1 TeV. The vacuum stability of the SM Higgs boson up to the Planck scale is also achieved by this simple extension of SM. Two models have been considered in this dissertation to achieve gauge coupling unification and vacuum stability, in the first model only vector-like fermions are added in the SM, where in the second model a potentially successful Dark Matter candidate is also considered along with the vector-like fermions. For describing the tiny neutrino masses, type I seesaw has also been included in the analysis and the impact of type I