Abstract

This thesis presents a study on phenomenology of beyond the Standard Model (SM) in the context of extensions of supersymmetric realisations. This extended framework allows us to accommodate viable dark matter (DM) candidates which the SM do not have, and it offers a unified gauge structure for all three nuclear forces. With this motivation, we investigated two possible extensions of MSSM and their predictabilities in future collider experiments.

First, we presented an extension of MSSM via vector-like (VL) supermultiplets which can provide new annihilation channels for dark matter. We investigate a simple extension with two VL pairs of weak doublets (lepton and down-type quark) and a pair of VL-neutrino singlets. Both neutralino and sneutrinos can emerge as viable DM candidates in such a framework. A complete analysis has been conducted on the DM. Furthermore, we investigate specific collider signatures that such construction can bring and demonstrate the enhanced production of events fortified with tau leptons.

Secondly, we investigated U(1) extensions of the MSSM framework within E6 gauge structure by conducting a detailed analysis of the parameter space that can emerge through a variety of U(1)' charge structures. Such a scenario predicts two DM candidates, neutralino and sneutrino. We presented a detailed analysis of low energy and cosmological observables. It is also vital to present the specific signatures that such gauge structure can bring into collider experiments. A heavy Z' boson is one of the identifying features of such a framework. We investigated possible loopholes in analyses where we observed that Z' mass bounds can be relaxed up to 300 GeV by changing the boundary conditions on the gauge couplings. We presented possible leptophobic scenarios which can be observed through supersymmetric cascade decays up to $7\sigma$ statistical significance at $ \sqrt{s}=14 $~TeV with 3 ab-1 integrated luminosity.

Finally, we revisited the current LHC bounds on supersymmetric particles in the light of theoretical uncertainties and studied high luminosity predictions. We investigated the effects of these uncertainties on gluino, squark mass limits and on coupling sensitivity of simplified s-channel DM models.