Study of Z plus b JETS production at LHC energies using CMS detector

Abstract

The physics analysis presented in this thesis is based on the measurement of the fiducial cross section for the production of a Z boson in association with at least one bottom quark jet. This is the first measurement of these processes based on data collected by the CMS experiment at a center-of-mass energy of 13TeV during the 2016 18 data-taking period. The dataset corresponds to an integrated luminosity of 137 fb-1. The Z + b-jets is a crucial process at the LHC for precision testing of electroweak and perturbative quantum chromodynamics (pQCD) calculations as it involves an electroweak and strong vertex in hadronic collisions. The b quark mass is above QCD scales so their production is not affected by low energy hadronization effects and is directly described by pQCD more precisely than a light-flavored jet. Understanding and modeling of pQCD interactions are important because they can affect the accuracy levels when we proceed with theoretical predictions. In pQCD, the amplitude for Z+b-jets processes can be computed using different parton distribution functions which provide information about the b quark content of the proton and also helps us to scrutinize the theoretical calculations by comparing predictions with experimental data. This comparison can help to improve the modeling of the production of b quarks. It is observed that the measured fiducial cross sections and shapes of the kinematic observables are not completely described by all predictions.