UC Berkeley

Inclusive ϒ(1S) and ϒ(2S) production have been measured in Pb–Pb collisions at the centre-of-mass energy per nucleon–nucleon pair s NN = 5.02 TeV, using the ALICE detector at the CERN LHC. The ϒ mesons are reconstructed in the centre-of-mass rapidity interval 2.5 < y < 4 and in the transverse-momentum range p T < 15 GeV/c, via their decays to muon pairs. In this Letter, we present results on the inclusive ϒ(1S) nuclear modification factor R AA as a function of collision centrality, transverse momentum and rapidity. The ϒ(1S) and ϒ(2S) R AA , integrated over the centrality range 0–90%, are 0.37 ± 0.02 ( stat ) ± 0.03 ( syst ) and 0.10 ± 0.04 ( stat ) ± 0.02 ( syst ) , respectively, leading to a ratio R AA ϒ ( 2S ) / R AA ϒ ( 1S ) of 0.28 ± 0.12 (stat) ± 0.06 (syst) . The observed ϒ(1S) suppression increases with the centrality of the collision and no significant variation is observed as a function of transverse momentum and rapidity.