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Free keywords:
Electroweak Interaction, Hadron-Hadron Scattering , QCD
MPINP:
LHCb - Abteilung Hinton
Abstract:
The first measurement of the Z boson production cross-section at centre-of-mass energy √s = 5.02 TeV in the forward region is reported, using pp collision data collected by the LHCb experiment in year 2017, corresponding to an integrated luminosity of 100 ± 2 pb−1. The production cross-section is measured for final-state muons in the pseudorapidity range 2.0 < η < 4.5 with transverse momentum pT > 20 GeV/c. The integrated cross-section is determined to be
σZ→μ+μ− = 39.6 ± 0.7(stat) ± 0.6(syst) ± 0.8(lumi) pb
for the di-muon invariant mass in the range 60 < Mμμ < 120 GeV/c2. This result and the differential cross-section results are in good agreement with theoretical predictions at next-to-next-to-leading order in the strong coupling constant.
Based on a previous LHCb measurement of the Z boson production cross-section in pPb collisions at √sNN = 5.02 TeV, the nuclear modification factor RpPb is measured for the first time at this energy. The measured values are 1.2−0.3+0.5 (stat) ± 0.1(syst) in the forward region (1.53 < yμ∗ < 4.03) and 3.6−0.9+1.6 (stat) ± 0.2 (syst) in the backward region (−4.97 < yμ∗ < −2.47), where yμ∗ represents the muon rapidity in the centre-of-mass frame