Measurement of the forward W boson cross-section in pp collisions at √s = 7 TeV

Abstract

A measurement of the inclusive W → μν production cross-section using data from pp collisions at a centre-of-mass energy of √s=7 TeV is presented. The analysis is based on an integrated luminosity of about 1.0 fb[superscript −1] recorded with the LHCb detector. Results are reported for muons with a transverse momentum greater than 20 [GeV over c] and pseudorapidity between 2.0 and 4.5. The W [superscript +] and W [superscript −] production cross-sections are measured to be σW[superscript +]→μ[superscript +]ν=861.0±2.0±11.2±14.7pb, σW[superscript −]→μ[superscript −] [bar over ν] = 675.8±1.9±8.8±11.6pb,

where the first uncertainty is statistical, the second is systematic and the third is due to the luminosity determination. Cross-section ratios and differential distributions as functions of the muon pseudorapidity are also presented. The ratio of W [superscript +] to W [superscript −] cross-sections in the same fiducial kinematic region is determined to be σW [superscript +] → μ [superscript +] ν [over σW [superscript −] → μ [superscript −] [bar over ν]] = 1.274±0.005±0.009,

where the uncertainties are statistical and systematic, respectively. Results are in good agreement with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics.