Centrality dependence of ψ(2S) suppression in p-Pb collisions at √sNN=5.02 TeV

Abstract

The inclusive production of the (2S) charmonium state was studied as a function of centrality in p-Pb collisions at the nucleon-nucleon center of mass energy

√sNN = 5.02TeV at the CERN LHC. The measurement was performed with the ALICE detector in the center of mass rapidity ranges -4:46 < ycms < -2:96 and 2:03 < ycms < 3:53, down to zero transverse momentum, by reconstructing the (2S) decay to a muon pair. The (2S) production cross section (2S) is presented as a function of the collision centrality, which is estimated through the energy deposited in forward rapidity calorimeters. The relative strength of nuclear e ects on the (2S) and on the corresponding 1S charmonium state J/ is then studied by means of the double ratio of cross sections [σ ψ(2S) /σJ/ψ ]pPb /[σ ψ(2S) /σJ/ψ ]pp between p-Pb and pp collisions, and by the values of the nuclear modi cation factors for the two charmonium states. The results show a large suppression of ψ(2S) production relative to the J/ψ at backward (negative) rapidity, corresponding to the ight direction of the Pb-nucleus, while at forward (positive) rapidity the suppressions of the two states are comparable. Finally, comparisons to results from lower energy experiments and to available theoretical models are presented.