Abstract
The production of J/ψ mesons is studied in proton-lead collisions at the centre-of-mass energy per nucleon pair sNN=8.16 TeV with the LHCb detector at the LHC. The double differential cross-sections of prompt and nonprompt J/ψ production are measured as a function of the J/ψ transverse momentum and rapidity in the nucleon–nucleon centre-of-mass frame. Forward-to-backward ratios and nuclear modification factors are determined. The results are compared with theoretical calculations based on collinear factorisation using nuclear parton distribution functions, on the colour glass condensate or on coherent energy loss models.
Highlights
The production of J /ψ mesons, and more generally of quarkonium states, has been considered as a sensitive probe of colour screening in a hot and dense medium since the proposal by Matsui and Satz in 1986 [1] of the suppression of the J /ψ meson production in heavy-ion collisions as a sign of deconfinement
Small-angle gluon radiation taking into account interference between initial and final state radiation, called coherent energy loss, was proposed as the dominant nuclear modification of quarkonium production in proton-lead collisions [25]
We describe the measurement of the doubledifferential production cross-sections of J /ψ mesons as a function of pT and y∗ in the ranges 0 < pT < 14 GeV/c and 1.5 < y∗ < 4.0 for pPb and −5.0 < y∗ < −2.5 for Pbp
Summary
The production of J /ψ mesons, and more generally of quarkonium states, has been considered as a sensitive probe of colour screening in a hot and dense medium since the proposal by Matsui and Satz in 1986 [1] of the suppression of the J /ψ meson production in heavy-ion collisions as a sign of deconfinement. Small-angle gluon radiation taking into account interference between initial and final state radiation, called coherent energy loss, was proposed as the dominant nuclear modification of quarkonium production in proton-lead collisions [25] The discrimination between these phenomena is a strong motivation for the study of the production of quarkonium as a hard-scale probe of QCD at high density. The measurements of the production of prompt J /ψ and nonprompt J /ψ mesons, called J /ψ -from-b-hadrons in the following, presented in this letter are important ingredients for the understanding of the imprints of deconfinement in nucleus–nucleus collisions They are based on larger integrated luminosities and on higher collision energies than 2013 proton-lead data sample the initial measurements w√ith by the LHCb experiment at sN the N=. The forward-to-backward ratio is measured as the ratio of crosssections in the positive and negative y∗ acceptances evaluated in the same absolute y∗ value ranges,
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