Abstract
The production cross-sections of J/ψ mesons in proton-proton collisions at a centre-of-mass energy of sqrt{s} = 5 TeV are measured using a data sample corresponding to an integrated luminosity of 9.13 ± 0.18 pb−1, collected by the LHCb experiment. The cross-sections are measured differentially as a function of transverse momentum, pT, and rapidity, y, and separately for J/ψ mesons produced promptly and from beauty hadron decays (nonprompt). With the assumption of unpolarised J/ψ mesons, the production cross-sections integrated over the kinematic range 0 < pT< 20 GeV/c and 2.0 < y < 4.5 areσpromptJ/ψ=8.154±0.010±0.283μb,σnonpromptJ/ψ=0.820±0.003±0.034μb,\\documentclass[12pt]{minimal}\t\t\t\t\\usepackage{amsmath}\t\t\t\t\\usepackage{wasysym}\t\t\t\t\\usepackage{amsfonts}\t\t\t\t\\usepackage{amssymb}\t\t\t\t\\usepackage{amsbsy}\t\t\t\t\\usepackage{mathrsfs}\t\t\t\t\\usepackage{upgreek}\t\t\t\t\\setlength{\\oddsidemargin}{-69pt}\t\t\t\t\\begin{document}$$ {\\displaystyle \\begin{array}{c}{\\sigma}_{\\mathrm{prompt}}\\ J/\\psi =8.154\\pm 0.010\\pm 0.283\\ \\upmu \\mathrm{b},\\\\ {}{\\sigma}_{\\mathrm{nonprompt}}\\ J/\\psi =0.820\\pm 0.003\\pm 0.034\\ \\upmu \\mathrm{b},\\end{array}} $$\\end{document}where the first uncertainties are statistical and the second systematic. These cross-sections are compared with those at sqrt{s} = 8 TeV and 13 TeV, and are used to update the measurement of the nuclear modification factor in proton-lead collisions for J/ψ mesons at a centre-of-mass energy per nucleon pair of sqrt{s_{mathrm{NN}}} = 5 TeV. The results are compared with theoretical predictions.
Highlights
Background tz modelSignal tz modelTracking efficiency particle identification (PID) efficiency Hardware-trigger efficiency Software-trigger efficiencySimulation sample sizeB(J/ψ → μ+μ−) Luminosity Radiative tailCorrelations Uncorrelated Correlated between intervals UncorrelatedCorrelated between pT intervalsCorrelated between intervals Correlated between intervals Correlated between intervals Correlated between intervalsCorrelated between intervals Correlated between intervals Correlated between intervalsThe measured double-differential cross-sections for prompt and nonprompt J/ψ mesons are shown in figure 2 and listed in tables 2 and 3 in appendix A, for the range 0 < pT < 14 GeV/c and 2.0 < y < 4.5 with ∆pT between 1 and 4 GeV/c and ∆y = 0.5
With the assumption of unpolarised J/ψ mesons, the production cross-sections integrated over the kinematic range 0 < pT < 20 GeV/c and 2.0 < y < 4.5 are σprompt J/ψ = 8.154 ± 0.010 ± 0.283 μb, σnonprompt J/ψ = 0.820 ± 0.003 ± 0.034 μb, where the first uncertainties are statistical and the second systematic
√ This paper reports a J/ψ cross-section measurement in pp collisions at s = 5 TeV using a data sample collected by the LHCb experiment, corresponding to an integrated luminosity of 9.13 ± 0.18 pb−1 [33]
Summary
The LHCb detector [35, 36] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks. The online event selection is performed by a trigger, which consists of a hardware stage, based on information from the calorimeter and muon systems, followed by a software stage, which applies a full event reconstruction. The J/ψ candidates are reconstructed through the J/ψ →μ+μ− decay channel and are selected through two trigger stages. The hardware trigger selects events with at least one muon candidate with pT > 900 MeV/c. The software trigger requires two loosely identified muons, having pT > 500 MeV/c and p > 3000 MeV/c, to form a good-quality vertex. Where zJ/ψ and zPV are positions the J/ψ decay vertex and the PV along the beam axis z, pz is the projection of the measured momentum of the J/ψ candidate along the z axis, and mJ/ψ is the known J/ψ mass [47]. Candidates with |tz| < 10 ps and σtz < 0.3 ps are selected for further analysis
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