Measurement of the Production Cross-Section of Z→ μ+μ− with ATLAS at the LHC at √s = 7 TeV

This thesis presents measurements of the inclusive process pp → (Z → μ+ μ− ) + anything based on 40.2 pb−1 of data from LHC collisions with center-of-mass energy of √s = 7 TeV as recorded by the ATLAS detector. For events with two isolated muons satisfying transverse momentum (pT )μ > 20 GeV, pseudorapidity |(η)μ | < 2.4, and dimuon invariant mass 60 < Mμμ < 120 GeV, the product of the fiducial Z production cross-section and branching ratio to muons was determined to be (σ Z )fid × BRμμ = 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, (σ Z )tot × BRμμ = 0.943 ± 0.041 nb. Normalized distributions for the transverse momentum and rapidity of Z/γ∗ → μ+ μ− muon pairs were also measured and found to be in good agreement with theory modeled by the Pythia Monte Carlo program.