Prompt and non-prompt J / ψ and ψ ( 2 S ) suppression at high transverse momentum in 5.02 TeV Pb+Pb collisions with the ATLAS experiment

Abstract

A measurement of $J/\psi$ and $\psi \left(2S\right)$ production is presented. It is based on a data sample from Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$ and pp collisions at $\sqrt{s}=5.02\mathrm{TeV}$ recorded by the ATLAS detector at the LHC in 2015, corresponding to an integrated luminosity of $0.42{\mathrm{nb}}^{-1}$ and $25{\mathrm{pb}}^{-1}$ in Pb+Pb and pp, respectively. The measurements of per-event yields, nuclear modification factors, and non-prompt fractions are performed in the dimuon decay channel for $9<p_T^{\mu \mu }<40$ GeV in dimuon transverse momentum, and $-2<y_{\mu \mu }<2$ in rapidity. Strong suppression is found in Pb+Pb collisions for both prompt and non-prompt $J/\psi$ , increasing with event centrality. The suppression of prompt $\psi \left(2S\right)$ is observed to be stronger than that of $J/\psi$ , while the suppression of non-prompt $\psi \left(2S\right)$ is 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. Despite prompt and non-prompt $J/\psi$ arising from different mechanisms, the dependence of their nuclear modification factors on centrality is found to be quite similar.