Measurement of J/ψ production in Pb—Pb and pp collisions at the LHC with the ALICE experiment

ALICE (A Large Ion Collider Experiment) aims to study the behaviour of nuclear matter at high energy densities and the transition to Quark Gluon Plasma (QGP), expected to occur in relativistic heavy ion collisions. Quarkonia are important probes of nuclear matter and QGP, through the modification of their yield in the hot and dense medium formed in heavy ion collisions. Their measurement in pp collisions is also crucial to the ALICE physics program. ALICE measures quarkonium production at both forward (in the dimuon channel) and mid-rapidity (in the dielectron channel). In 2010 and 2011 the Large Hadron Collider has provided pp collisions at √S = 7 TeV and 2.76 TeV and Pb-Pb collisions at √SNN = 2.76 TeV. The ALICE results on J/ψ production in both Pb-Pb and pp collisions are presented.