Quarkonia as probes of the QGP and the initial stages of the heavy-ion collisions with ALICE

TL;DR

This paper discusses how quarkonium measurements in heavy-ion collisions, especially by ALICE at the LHC, can reveal properties of the quark-gluon plasma, initial collision stages, and nuclear gluon distributions.

Contribution

It presents recent ALICE measurements of quarkonium suppression, polarization, and photoproduction in Pb-Pb collisions at 5.02 TeV, providing new insights into QGP properties and initial collision dynamics.

Findings

Preliminary J/ψ R_AA measurements at different rapidities.

First polarization measurements of J/ψ in Pb-Pb collisions.

Initial estimates of coherent J/ψ photoproduction cross section.

Abstract

Studies of quarkonium production in heavy-ion collisions can be used for probing QGP properties. The suppression and regeneration of bound quarkonium states is sensitive to the medium properties. Modifications of the quarkonium polarization in Pb-Pb collisions with respect to pp collisions may give further insight into the suppression and regeneration mechanisms in the QGP. Quarkonia are also sensitive to the initial stages of heavy-ion collisions, and measurements in photonuclear collisions may help constrain the nuclear gluon-distribution at low Bjorken-$x$. In this work, recent quarkonium measurements performed by ALICE in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeV will be discussed. Preliminary measurements of the inclusive J/$\psi$ $R_{\rm AA}$ measured at both forward and midrapidity will be presented. The J/$\psi$ polarization measured for the first time in Pb-Pb collisions, as well as preliminary measurements of the coherent J/$\psi$ photoproduction cross section, will be discussed.