Charmonium production in p-Pb collisions with ALICE at the LHC

TL;DR

This paper reports on the measurement of J/ψ production in p-Pb collisions at the LHC, aiming to distinguish cold nuclear matter effects from quark-gluon plasma signatures by analyzing nuclear modification factors across different energies.

Contribution

First measurement of inclusive J/ψ nuclear modification factor in p-Pb collisions at 8.16 TeV, comparing results with previous 5.02 TeV data to understand cold nuclear matter effects.

Findings

Nuclear modification factor varies with centrality.

Comparison shows energy dependence of suppression.

Results help disentangle QGP and CNM effects.

Abstract

The suppression of quarkonium production with respect to pp collisions is one of the most distinctive signatures of the formation of quark-gluon plasma (QGP), a hot nuclear medium created in ultrarelativistic heavy-ion collisions. However, the suppression of heavy quarkonium production with respect to pp collisions can also take place in p-A collisions, where QGP is not expected to be created and only cold nuclear matter (CNM) effects, such as nuclear absorption, parton shadowing and parton energy loss in initial and final states occur. The study of p-A collisions is therefore important to disentangle the effects of QGP from the CNM ones, and to provide essential input to understand the nucleus-nucleus collisions. The ALICE Collaboration at the LHC has studied inclusive J/$\psi$ production, in the dimuon decay channel, at forward rapidity (2.03 $<$ $y_{\rm cms}$ $<$ 3.53) and backward rapidity ($-$4.46 $<$ $y_{\rm cms}$ $<$ $-$2.96) in p-Pb collisions at $\sqrt{s_{\rm NN}} = 8.16$ TeV with the Muon Spectrometer. In this contribution, we present the measurement of the nuclear modification factor of inclusive J/$\psi$ as a function of the centrality and we show the comparison of this result with the one at $\sqrt{s_{\rm NN}} = 5.02$ TeV.