Measurement of Υ(1S) elliptic flow at forward rapidity in Pb-Pb collisions at √sNN=5.02 TeV

Abstract

The first measurement of the ϒ(1S) elliptic flow coefficient (v2) is performed at forward rapidity (2.5 <y< 4) in Pb–Pb collisions at √sNN = 5.02 TeV with the ALICE detector at the LHC. The results are obtained with the scalar product method and are reported as a function of transverse momentum (pT ) up to 15 GeV=c in the 5%–60% centrality interval. The measured ϒð1SÞv2 is consistent with 0 and with the small positive values predicted by transport models within uncertainties. The v2 coefficient in 2 < pT < 15 GeV=c is lower than that of inclusive J=ψ mesons in the same pT interval by 2.6 standard deviations. These results, combined with earlier suppression measurements, are in agreement with a scenario in which the ϒð1SÞ production in Pb–Pb collisions at LHC energies is dominated by dissociation limited to the early stage of the collision, whereas in the J=ψ case there is substantial experimental evidence of an additional regeneration component.