A measurement of J/ ψ and ψ(2 S) production is presented. It is based on a data sample from Pb+Pb collisions at sNN=5.02TeV and pp collisions at s=5.02TeV recorded by the ATLAS detector at the LHC in 2015, corresponding to an integrated luminosity of 0.42nb-1 and 25pb-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<pTμμ<40 GeV in dimuon transverse momentum, and - 2 < y μμ < 2 in rapidity. Strong suppression is found in Pb+Pb collisions for both prompt and non-prompt J/ ψ, increasing with event centrality. The suppression of prompt ψ(2 S) is observed to be stronger than that of J/ ψ, while the suppression of non-prompt ψ(2 S) is 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. Despite prompt and non-prompt J/ ψ arising from different mechanisms, the dependence of their nuclear modification factors on centrality is found to be quite similar.

Aaboud, M., Aad, G., Abbott, B., Abdinov, O., Abeloos, B., Abidi, S.H., et al. (2018). Prompt and non-prompt J/ ψ and ψ(2 S) suppression at high transverse momentum in 5.02TeV Pb+Pb collisions with the ATLAS experiment. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS, 78(9) [10.1140/epjc/s10052-018-6219-9].

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

Ceradini, F.;Di Micco, B.;Di Nardo, R.;Orestano, D.;