Inclusive W and Z production in the forward region at √s = 7\,TeV

A bstract 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 ± 29pb for W + , 656 ± 8 ± 19 ± 23 for W − and 76 . 7 ± 1 . 7 ± 3 . 3 ± 2 . 7pb 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⁻ ν = 1.27± 0.02± 0.01 and ( σ_W⁺ → μ⁺ν + σ_W⁻ → μ⁻ ν )/σ_Z → μ μ = 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.