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

A measurement of $J/\psi$ and $\psi(2S)$ production is presented. It is based on data from lead-lead collisions at $\sqrt{s_{NN}}=5.02$ TeV and pp collisions at $\sqrt{s}=5.02$ TeV recorded by the ATLAS detector at the LHC in 2015, corresponding to integrated luminosities of 0.49 $\mathrm{nb}^{-1}$ and 25 $\mathrm{pb}^{-1}$ 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 $J/\psi$, as well as for prompt and non-prompt $\psi(2S)$, becoming more pronounced with increasing event centrality. The suppression of prompt $\psi(2S)$ was observed to be stronger than that of $J/\psi$, while the suppression of non-prompt $\psi(2S)$ was equal to that of the non-prompt $J/\psi$ 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 $J/\psi$ 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.