Differential studies of inclusive J/ ψ and ψ (2S) production at forward rapidity in Pb-Pb collisions at s N N = 2.76 TeV

The production of J/ ψ and ψ (2S) was studied with the ALICE detector in Pb-Pb collisions at the LHC. The measurement was performed at forward rapidity (2.5 < y < 4) down to zero transverse momentum ( p t ) in the dimuon decay channel. Inclusive J/ ψ yields were extracted in different centrality classes and the centrality dependence of the average p t is presented. The J/ ψ suppression, quantified with the nuclear modification factor ( R AA ), was measured as a function of centrality, transverse momentum and rapidity. Comparisons with similar measurements at lower collision energy and theoretical models indicate that the J/ ψ production is the result of an interplay between color screening and recombination mechanisms in a deconfined partonic medium, or at its hadronization. Results on the ψ (2S) suppression are provided via the ratio of ψ (2S) over J/ ψ measured in pp and Pb-Pb collisions.