Inclusive W and Z Production in the Forward Region at √s = 7 TeV

Measurements of inclusive W and Z boson production cross-sections in pp collisions at √s = 7 TeV using final states containing muons are presented. The data sample corresponds to an integrated luminosity of 37 pb^−1 collected with the LHCb detector. The W and Z bosons are reconstructed from muons with a transverse momentum above 20 GeV/c and pseudorapidity between 2.0 and 4.5, and, in the case of the Z cross-section, a dimuon invariant mass between 60 and 120 GeV/c^2. The cross-sections are measured to be 831 ± 9 ± 27 ± 29 pb for W+, 656 ± 8 ± 19 ± 23 for W− and 76.7 ± 1.7 ± 3.3 ± 2.7 pb for Z, where the first uncertainty is statistical, the second is systematic and the third is due to the luminosity. Differential cross-sections, W and Z cross-section ratios and the lepton charge asymmetry are also measured in the same kinematic region. The ratios are determined to be σ_{W+ → μ+ ν}/σ_{W− → μ− anti-ν} = 1.27 ± 0.02 ± 0.01 and (σ_{W+ → μ+ ν} + σ_{W− → μ− anti-ν}) / σ_{Z → μμ} = 19.4 ± 0.5 ± 0.9. The results are in general agreement with theoretical predictions, performed at next-to-next-to-leading order in QCD using recently calculated parton distribution functions.