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=5.02 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 pT<15 GeV/c, via their decays to muon pairs. In this Letter, we present results on the inclusive ϒ(1S) nuclear modification factor RAA as 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 RAAϒ(2S)/RAAϒ(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.
Highlights
A detailed study of the properties of the Quark-Gluon Plasma (QGP) [1] is the main goal of heavy-ion experiments at ultra-relativistic energies [2,3,4,5,6]
The bottomonium suppression due to the QGP should be disentangled from the suppression due to Cold Nuclear Matter (CNM) effects, such as the nuclear modification of the parton distribution functions due to shadowing [36, 37], as well as parton energy loss [38]
These effects on the bottomonium production were studied in p–Pb collisions by ALICE [39] and LHCb [40], who reported for the Υ(1S) a nuclear modification factor slightly lower than unity at forward rapidity and compatible with unity at backward rapidity, with significant uncertainties
Summary
A detailed study of the properties of the Quark-Gluon Plasma (QGP) [1] is the main goal of heavy-ion experiments at ultra-relativistic energies [2,3,4,5,6]. The bottomonium suppression due to the QGP should be disentangled from the suppression due to Cold Nuclear Matter (CNM) effects, such as the nuclear modification of the parton distribution functions due to shadowing [36, 37], as well as parton energy loss [38] These effects on the bottomonium production were studied in p–Pb collisions by ALICE [39] and LHCb [40], who reported for the Υ(1S) a nuclear modification factor slightly lower than unity at forward rapidity and compatible with unity at. Additional measurements at forward/backward rapidity with higher statistics, are needed to fully constrain the models and perform a meaningful extrapolation of CNM effects to Pb–Pb collisions In this tion in Letter we present the first results Pb–Pb collisions at √sNN = 5.02 on the Υ(1S) and Υ(2S) RAA measured by the ALICE CollaboraTeV.
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