Abstract
The first measurement of the ϒ(1S) elliptic flow coefficient (v_{2}) is performed at forward rapidity (2.5<y<4) in Pb-Pb collisions at sqrt[s_{NN}]=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 (p_{T}) up to 15 GeV/c in the 5%-60% centrality interval. The measured ϒ(1S)v_{2} is consistent with 0 and with the small positive values predicted by transport models within uncertainties. The v_{2} coefficient in 2<p_{T}<15 GeV/c is lower than that of inclusive J/ψ mesons in the same p_{T} interval by 2.6 standard deviations. These results, combined with earlier suppression measurements, are in agreement with a scenario in which the ϒ(1S) 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.
Highlights
At the extreme energy densities and temperatures produced in ultrarelativistic collisions of heavy nuclei, hadronic matter undergoes a transition into a state of deconfined quarks and gluons, known as quark-gluon plasma (QGP)
Quarkonium production is suppressed by color screening inside the QGP medium created in nucleus-nucleus collisions [12]
This effect originates from regeneration of charmonia via recombination of thermalized charm quarks either during the QGP evolution [18,19] or at the QGP phase boundary [20,21]
Summary
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. 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.
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