ϒ suppression at forward rapidity in Pb–Pb collisions at √sNN = 5.02 TeV

Abstract

Inclusive ϒ(1S)and ϒ(2S)production have been measured in Pb–Pb collisions at the centre-of-mass energy per nucleon–nucleon pair √sNN=5.02TeV, using the ALICE detector at the CERN LHC. The ϒmesons are reconstructed in the centre-of-mass rapidity interval 2.5 <y <4and in the transverse-momentum range pT<15GeV/c, via their decays to muon pairs. In this Letter, we present results on the inclusive ϒ(1S)nuclear modification factor RAAas a function of collision centrality, transverse momentum and rapidity. The ϒ(1S)and ϒ(2S)RAA, 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 Rϒ(2S)AA/Rϒ(1S)AAof 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.