Measurement of the forward Z boson production cross-section in pp collisions at TeV

Abstract

A measurement of the production cross-section for Z bosons that decay to muons is presented. The data were recorded by the LHCb detector during pp collisions at a centre-of-mass energy of 7 TeV, and correspond to an integrated luminosity of 1.0 fb−1 . The cross-section is measured for muons in the pseudorapidity range 2.0 < η < 4.5 with transverse momenta pT > 20 GeV/c. The dimuon mass is restricted to 60 < Mµ+µ− < 120 GeV/c2 . The measured cross-section is σZ→µ+µ− = (76.0 ± 0.3 ± 0.5 ± 1.0 ± 1.3) pb where the uncertainties are due to the sample size, systematic effects, the beam energy and the luminosity. This result is in good agreement with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. The cross-section is also measured differentially as a function of kinematic variables of the Z boson. Ratios of the production cross-sections of electroweak bosons are presented using updated LHCb measurements of W boson production. A precise test of the Standard Model is provided by the measurement of the ratio