GEM Performance Studies in CMS Experiment with Four Muons Final State

The standard model (SM) of particle physics, although it is a very successful theory and compatible with all experimental results, it has a number of shortcomings, in particular it provides no answer for the three generations of fermions. Compositeness models try to solve this problem by postulating that quarks and leptons might be composite objects of fundamental particles. Due to their substructure, these models predict the existence of excited states of SM particles, in particular excited quarks $q^*$ and excited leptons $l^*$. In the first part of the thesis we present a phenomenological study of excited muons $\mu^*$ at center of mass energy $\sqrt{s}$ = 14 TeV and integrated luminosity of $300fb^{-1}$ respectively. These excited muons are produced via contact interactions at an energy scale $\Lambda$ either singly in conjunction with a SM particle or in pairs. The considered channel here is the single production, in particular the decay channel $pp \rightarrow \mu \mu^* \rightarrow \mu \mu Z$, with the Z gauge boson decaying into two muons. So there will be 4$\mu$ final state, and it will be considered as a signature in the detector. \newline Although this branching ration is small; it is considered a clean channel. The main irreducible background is $pp \rightarrow ZZ \rightarrow 4 \mu $. It is irreducible and overwhelming contributes about 90\% of the total background expectations. The compositeness scale $\Lambda$, and the mass of the excited muon are free parameters in the theory. The mass range considered is between (0.5 $\sim$ 5 TeV) with a step of 0.5TeV, and a compositeness scale $\Lambda $ = 10 TeV. Signal samples are generated using Pythia 8.2 Monte Carlo event generator at Leading Order (LO) accuracy using CTEQ6L1 parton distribution function (PDF). The signal events are then passed to Delphes fast simulation tool to simulate the CMS detector response and reconstruct the final state particles. Some SM processes give the same final state as our signal, and is considered as a background. Background events is generated using Madgraph event generator interfaced with pythia for haronization and parton showering, and then passed to Delphes for detector simulation. In the second part of the thesis, we provide a GEM performance study using the four muon channel of excited muons. Gas Electron Multiplier is gaseous detector that would be introduced in high eta end-cap region of CMS detector at 2019 for tracking and triggering of muons as it can effectively differentiate effectively between low p$_{T}$ and high p$_{T}$ muons. The installation of GEM will restore robustness and redundancy thereby affording fully efficient and clean reconstruction of muons by improving muon momentum resolution and providing a highly efficient trigger and reconstruction capability.