Abstract

The inclusive production of the charmonium state ψ ( 2 S ) was studied in p-Pb and Pb-Pb collisions at s NN = 8.16 TeV and 5.02 TeV respectively, using the ALICE detector at the CERN LHC. The ψ ( 2 S ) is less bound than the J / ψ and it represents an interesting probe for the study of cold nuclear matter effects in p-Pb collisions, while in the Pb-Pb system its formation can be strongly influenced by QGP production. The measurements are performed in different center-of-mass rapidity ranges, 2.03 < y cms < 3.53 and −4.46 < y cms < −2.96 for p-Pb collisions and 2.5 < y cms < 4.0 for Pb-Pb collisions, down to zero transverse momentum, through the ψ ( 2 S ) → μ + μ - decay channel. The results are compared to those obtained for the J / ψ and with theoretical predictions.

Highlights

  • The study of charmonia, bound states of a charm and anti-charm quarks, represents a research field of particular interest in the investigation of Quark-Gluon Plasma (QGP). The production of these mesons is expected to be modified in the QGP, by means of a screening mechanism due to the high density of colour charges [1]. This leads to a suppression of the charmonium yields in nucleus-nucleus collisions with respect to proton-proton collisions

  • At LHC energies, large number of ccpairs can be produced in each Pb-Pb collision, charmonium suppression can be partly counterbalanced by ageneration mechanism, which is related to the charmonium formation through the statistical recombination of charm quarks

  • These effects are studied in proton-nucleus collisions, where no QGP is expected to be formed and they are known as cold nuclear matter effects

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Summary

Introduction

The study of charmonia, bound states of a charm and anti-charm quarks (cc), represents a research field of particular interest in the investigation of Quark-Gluon Plasma (QGP). The production of these mesons is expected to be modified in the QGP, by means of a screening mechanism due to the high density of colour charges [1] This leads to a suppression of the charmonium yields in nucleus-nucleus collisions with respect to proton-proton collisions. Charmonia can be dissociated by interacting with colliding nuclei This effect, named nuclear absorption, is relevant when the formation time of the resonance is smaller than the time spent by the ccinside the nucleus and it is not important at LHC energies. In these proceedings ALICE results on ψ(2S) production are shown as a function of rapidity, transverse momentum and centrality in p-Pb collisions at sNN =.

Analysis Technique
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Conclusions

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