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

TL;DR

This paper reports on measurements of charmonium production, specifically J/ψ and ψ(2S), in Pb-Pb collisions at the LHC at two different energies, providing insights into quark-gluon plasma effects through nuclear modification factors.

Contribution

It presents new J/ψ production results at 5.02 TeV and compares them with previous data and theoretical models, enhancing understanding of QGP effects on charmonium.

Findings

Nuclear modification factor varies with collision centrality and kinematic variables.

New results at 5.02 TeV show differences compared to 2.76 TeV data.

Comparison with models helps constrain QGP formation theories.

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.