Speaker
Description
Charmonium production is a crucial observable in pp and A-A collisions.
Studies on charmonium production in pp collisions can help to understand both fundamental perturbative QCD processes $i.e.$ the initial charm-quark pair production, as well as hadronization mechanisms $i.e.$ the subsequent binding into a charmonium state. $J/\psi$ measurements as a function of multiplicity can help to explore the interplay between the hard and soft relevant mechanisms.
In the study of charmonium in A-A collisions, several QGP effects have been observed, such as the suppression of charmonium states due to color screening. In addition, an enhancement due to (re)combination of uncorrelated charm and anti-charm quarks is also present at LHC energies. This enhancement is more pronounced at low transverse momentum ($p_{\rm T} < $ 4.0 GeV/$c$).
ALICE measures $J/\psi$ production in the mid-rapidity ($|y|<0.9$) and forward-rapidity ($2.5 < y < 4.0$) regions down to $p_{\rm T}$ = 0. In this talk, ALICE measurements in pp collisions at $\sqrt{s}$ = 13 TeV as a function of charged-particle multiplicity will be shown. The inclusive $J/\psi$ nuclear modification factor ($R_{\rm AA}$) in Pb-Pb and Xe-Xe collisions as a function of centrality and $p_{\rm T}$ will be discussed as well and compared to model predictions.
