J/ψ production in Pb–Pb collisions at √(s_NN)=2.76 TeV

ALICE at the Large Hadron Collider (LHC) provides unique capabilities to study charmonium production at low transverse momenta. In the early stage of nucleus–nucleus collisions the formation of a Quark–Gluon Plasma (QGP) is expected. Several QGP induced effects, such as the melting of charmonium states due to color screening and/or a (re)combination of charm and anti-charm quarks, can play a role. A suppression with respect to pp collisions of charmonium states such as the J/ψ was indeed observed in heavy-ion collisions. The corresponding measurements in pp and p–Pb collisions are crucial for the understanding of the Pb–Pb results. At central (forward) rapidity, corresponding to the range |y|<0.9 (2.5AA as a function of collision centrality, rapidity and transverse momentum in Pb–Pb collisions at √(s_NN)=2.76 TeV are presented. Additionally, an estimation of the cold nuclear matter effects in Pb–Pb, derived from p–Pb measurements, is given. These measurements provide, in combination with results from lower energies and theoretical predictions, detailed information on the different mechanisms related to the presence of the hot medium produced in heavy-ion collisions