Analysis of WV scattering in leptonic decays using the CMS detector at LHC energies and projection for HL LHC using EFT model

Abstract

The Large Hadron Collider (LHC) at CERN is the world s largest and highest hadron collider, where proton-proton and proton-ion collisions occur at high energies. It plays a vital role in Standard Model (SM) precision measurements and the search for new physics. The discovery of the Higgs boson at CERN is a triumph of the SM. Despite this success, it is unable to account for a number of observed phenomena. This motivates to explore alternative theories beyond the SM (BSM) and necessitates to scrutinize the Electroweak Symmetry Breaking mechanism rigorously by carrying out the precision measurements of the Higgs boson properties and the couplings of the electroweak vector bosons (W, Z) via the Vector Boson Scattering (VBS). In this context, BSM effects in VBS processes are manifested with the help of Effective Field Theories (EFT). This thesis presents measurement of invariant full WZ mass using a new technique, cross-section measurements and anomalous quartic gauge coupling measurements for WZ channel, in the fully leptonic final state. In addition aQGC measurements for two combined final states of WW and WZ are also presented. The data used are pp collisions collected with the CMS detector at LHC during 2016 2018 at and#8730;s = 13 TeV, with an integrated luminosity of 137 fband#8722;1. Constraints are imposed on the VVVV couplings in the framework of dim-8 EFT operators at 95% confidence level. This thesis quantifies in terms of limits the significance of taking into account the appropriate EFT validity range, which is often overlooked in the data analyses. newlineThe analysis of BSM discovery potential for the same-sign WW scattering process in fully leptonic final states at the high- luminosity and high-energy phases of the LHC was also conducted. The goal was to investigate the applicability of EFT approach, to describe a hypothetical BSM signal in the WWWW quartic interaction. Discovery potential regions for 14 TeV (HE- LHC) and 27 TeV (HL-LHC) machines for all dimension-8 operators were computed. newline newline