Measurement of quarkonium production in proton-lead and proton-proton collisions at with the ATLAS detector.

The modification of the production of , , and ( ) in +Pb collisions with respect to their production in collisions has been studied. The +Pb and datasets used in this paper correspond to integrated luminosities of and respectively, collected in 2013 and 2015 by the ATLAS detector at the LHC, both at a centre-of-mass energy per nucleon pair of 5.02 TeV. The quarkonium states are reconstructed in the dimuon decay channel. The yields of and are separated into prompt and non-prompt sources. The measured quarkonium differential cross sections are presented as a function of rapidity and transverse momentum, as is the nuclear modification factor, for and . No significant modification of the production is observed while production is found to be suppressed at low transverse momentum in +Pb collisions relative to collisions. The production of excited charmonium and bottomonium states is found to be suppressed relative to that of the ground states in central +Pb collisions.