Estudo da quebra da simetria eletrofraca através do espelhamento W ±W ± no experimento CMS do CERN.

Abstract

This work presents a study of W+W+ and W−W− scattering for the first years of the CMS experiment data-taking at LHC, CERN. Vector boson scattering, including W±W±, is a key processes for probing electroweak symmetry breaking. Theoretical predictions show that kinematics characteristics of vector boson scattering at T e V scale must strongly depend on the electroweak symmetry breaking mechanism. This process is analyzed with two main objectives: viability study of performing this measurement at CMS and show its dependence on the electroweak symmetry breaking mechanism. This dependence is shown through an analysis with two event samples corresponding to two distinct scenarios: the standard model with the presence of a 500 GeV massive Higgs boson and the standard model without presence of a Higgs boson. These samples were generated by the Monte-Carlo generator PHASE, whose main importance for vector boson scattering at high energies is its characteristic of calculating the complete matrix elements in leading order O(α6). To analyze the viability of measuring the W±W± scattering at CMS, the simulated signal and background events were submitted to the CMS fast detector simulation, FAMOS. Background processes, WW+N jets, WZ+N jets, ZZ+N jets, W+N jets and t¯t+N jets, were studied and suppressed through kinematics region selection. Data analysis shows that the measurement of W±W± scattering in early stages of LHC will be very difficult, being necessary a larger luminosity, besides improvements on the analysis.