Charmonium production in Pb-Pb collisions measured by ALICE at the LHC

Abstract

The ALICE experiment is dedicated to the study of the Quark-Gluon Plasma (QGP), a state of matter where, due to high temperature and density, quarks and gluons are deconfined. One of the probes studied to investigate this state of matter is the production of charmonium states, such as the J/$\psi$ and the $\psi$(2S). Indeed, the presence of the QGP is expected to modify the charmonium production yields, due to a balance between the color screening of the charm quark potential and a recombination mechanism. A suppression of the production yields in heavy ion collisions with respect to pp collisions scaled by the mean number of binary nucleon-nucleon collisions was observed by ALICE in Pb-Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{ s_{NN}} = 2.76$ TeV. The observed suppression is smaller than the one found by PHENIX at an order of magnitude lower collision energy. This behavior can be explained by a stronger contribution from recombination processes at LHC than at lower energies. In this presentation, we report on new results for the charmonium production in Pb-Pb collisions measured at forward rapidity with the the muon spectrometer of ALICE at $\sqrt{ s_{NN}} =5.02$ TeV and their comparison with previous results and model predictions.