Charmonium production in Pb-Pb collisions at $\sqrt{s_{\rm NN}} =$ 2.76 and 5.02 TeV with ALICE

Abstract

The production of charmonium states, J/$\psi$ and $\psi$(2S), in heavy-ion collisions, is an important probe to investigate the formation of a plasma of quarks and gluons (QGP). In a hot and deconfined medium, quarkonium production is, indeed, expected to be significantly modified, with respect to the pp yields, due to a balance of color screening and charm-quark recombination mechanisms. The ALICE Collaboration at the LHC has measured charmonium production in Pb-Pb collisions at $\sqrt{s}_{\rm NN} =$ 2.76 and 5.02 TeV. The nuclear modification factor of inclusive J/$\psi$, evaluated at forward ($-4<\eta<-2.5$) rapidity, is measured as a function of the centrality of the collision and of the J/$\psi$ kinematic variables as transverse momentum and rapidity. In this article, we report on the new J/$\psi$ results, obtained at forward rapidity, at $\sqrt{s}_{\rm NN} = 5.02$ TeV. These new results are compared to the J/$\psi$ nuclear modification factor obtained at $\sqrt{s}_{\rm NN} =$ 2.76 TeV and to the available theoretical predictions.Comment: 4 pages, 4 figures, Strangeness in Quark Matter 2016, UC Berkeley, United States, 27 June-1 July, 201