Inclusive W and Z production in the forward region at sqrt(s) = 7 TeV

Measurements of inclusive W and Z boson production cross-sections in pp collisions at sqrt {s} = 7,{ ext{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/c2. 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 {sigma_{{{W^{ + }} o {mu^{ + }} u }}}/{sigma_{{{W^{ - }} o {mu^{ - }}overline u }}} = 1.27pm 0.02pm 0.01 and left( {{sigma_{{{W^{ + }} o {mu^{ + }} u }}} + {sigma_{{{W^{ - }} o {mu^{ - }}overline u }}}} ight)/{sigma_{{Z o mu mu }}} = 19.4pm 0.5pm 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.