ϒ production and nuclear modification at forward rapidity in Pb–Pb collisions at √sNN = 5.02 TeV

The production of Upsilon mesons in Pb-Pb collisions at a centre-of-mass energy per nucleon pair root S-NN = 5.02 TeV is measured with the muon spectrometer of the ALICE detector at the LHC. The yields as well as the nuclear modification factors are determined in the forward rapidity region 2.5 < y < 4.0, as a function of rapidity, transverse momentum and collision centrality. The results show that the production of the Upsilon(1S) meson is suppressed by a factor of about three with respect to the production in proton-proton collisions. For the first time, a significant signal for the Upsilon(2S) meson is observed at forward rapidity, indicating a suppression stronger by about a factor 2-3 with respect to the ground state. The measurements are compared with transport, hydrodynamic, comover and statistical hadronisation model calculations. (C) 2021 European Organization for Nuclear Research, ALICE. Published by Elsevier B.V.