Measurement of the Production Cross-Section of Z u+u- with ATLAS at the LHC at Vs=7 TeV.

Abstract

This thesis presents measurements of the inclusive process pp->(Z->mu+mu-)+anything based on 40.2~pb^-1 of data from LHC collisions with center-of-mass energy of sqrt(s)=7 TeV as recorded by the ATLAS detector. For events with two isolated muons satisfying transverse momentum (p_T)_mu>20 GeV, pseudorapidity |(eta)_mu|<2.4, and dimuon invariant mass 60<M_mumu<120 GeV, the product of the fiducial Z production cross-section and branching ratio to muons was determined to be (sigma_Z)_fid X BR_mumu=0.455 +/- 0.017 nb, in agreement with a Standard Model prediction of 0.447 +/- 0.022 nb. Using Monte Carlo programs this result was extrapolated to yield a result for the total Z production cross-section, (sigma_Z)_tot X BR_mumu=0.943 +/- 0.041 nb.

Normalized distributions for the transverse momentum and rapidity of Z/gamma^*->mu+mu- muon pairs were also measured and found to be in good agreement with theory modeled by the PYTHIA Monte Carlo program.