J/ψ and ψ(2S) production in pp and PbPb collisions at 5.02 TeV with ATLAS

A measurement of J/ψ and ψ(2S) production is presented. It is based on data from lead-lead collisions at sNN=5.02 TeV and pp collisions at s=5.02 TeV recorded by the ATLAS detector at the LHC in 2015, corresponding to integrated luminosities of 0.49 nb−1 and 25 pb−1 in Pb+Pb and pp, respectively. The measurements of differential cross sections, nuclear modification factors, and non-prompt fractions were performed in the dimuon decay channel. A strong suppression was found for both prompt and non-prompt J/ψ, as well as for prompt and non-prompt ψ(2S), becoming more pronounced with increasing event centrality. The suppression of prompt ψ(2S) was observed to be stronger than that of J/ψ, while the suppression of non-prompt ψ(2S) was equal to that of the non-prompt J/ψ within uncertainties, consistent with the expectation that both arise from b-quarks propagating through the medium. The dependence of nuclear modification factors with centrality for prompt and non-prompt J/ψ was found to have a similar form, despite the quite different physical origins expected to have given rise to their production: a composite meson formed within the medium and a b-quark propagating through and out of the medium, respectively.