Suppression of ψ(2S) production in p-Pb collisions at sNN−−−√ = 5.02 TeV

Abstract

This is the published version. Open Access, Copyright CERN, for the benefit of the ALICE Collaboration. Article funded by SCOAP3.The ALICE Collaboration has studied the inclusive production of the charmonium state ψ(2S) in proton-lead (p-Pb) collisions at the nucleon-nucleon centre of mass energy sNN−−−√ = 5.02 TeV at the CERN LHC. The measurement was performed at forward (2.03 < y cms < 3.53) and backward (−4.46 < y cms < −2.96) centre of mass rapidities, studying the decays into muon pairs. In this paper, we present the inclusive production cross sections σ ψ(2S), both integrated and as a function of the transverse momentum p T, for the two y cms domains. The results are compared to those obtained for the 1S vector state (J/ψ), by showing the ratios between the production cross sections, as well as the double ratios [σ ψ(2S) /σ J/ψ ]pPb /[σ ψ(2S) /σ J/ψ ]pp between p-Pb and proton-proton collisions. Finally, the nuclear modification factor for inclusive ψ(2S) is evaluated and compared to the measurement of the same quantity for J/ψ and to theoretical models including parton shadowing and coherent energy loss mechanisms. The results show a significantly larger suppression of the ψ(2S) compared to that measured for J/ψ and to models. These observations represent a clear indication for sizeable final state effects on ψ(2S) production

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