A design study of the production of Z bosons in association with b jet in final states with muons with the ATLAS detector at the LHC

Abstract

The Large Hadron Collider (LHC) is the machine that will provide the highest ever produced energy in the center of mass, reaching the value of s=14 TeV for proton-proton collisions and giving the possibility to produce particles with mass up to few TeV. The work presented in this thesis is carried on in the framework of one of the LHC experiments: the ATLAS experiment. It presents a study of the prospects for measuring the pp ¡ Z + b jet + X channel (where X states for everything in the final state produced in association to the leading process) considering the decay selection Z ¡ µ¢ µ£ and the identification of the b jet in an inclusive mode and through the semi-leptonic decay of the b jet into muons. This process is interested in its own and also as background for many Standard Model and beyond Standard Model physics processes. The wide kinematic range for production of Z + b jet serves as a testing ground for perturbative QCD predictions. In addition the cross section is sensitive to the b quark content in the proton and its precise measurement will help in reducing the current uncertainty on the partonic content of the proton (PDF's). Such uncertainty is presently affecting the potential for discovering new physics at LHC. The main aim of this work has been to develop analysis techniques in order to evaluate the contamination of the signal from backgrounds and to study possible methods to extract signal from such backgrounds. The study was performed using the signal and background events modelled with Monte Carlo generators. Full and fast simulation of the Atlas detector was performed to obtain realistic estimates of the sensitivity of the measurements. An estimation of the main contributors to the systematic uncertainties on signal cross section measurement has also been provided.