Quarkonium production in high-energy collisions is a valuable tool to study both perturbative and non-perturbative aspects of QCD. Charmonia, such as the J/ψ and ψ(2S), are bound states of charm and anti-charm quarks. The ψ(2S), being less bound than the J/ψ, is more sensitive to the quark-gluon plasma (QGP) formed in heavy-ion collisions. its suppression relative to the J/ψ can reveal how different states are modified in the QGP. The ψ(2S) to J/ψ yield ratio in Pb-Pb, compared to pp collisions, helps isolate medium effects. In this article, the current status of the analysis of inclusive J/ψ and ψ(2S) production at forward rapidity (2.5 ψ(2S)- to-J/ψ ratio is presented as a function of the charmonium transverse momentum (pT) and event centrality and is compared to the extrapolated ratio from pp collisions, and to existing theoretical models.
Sara Garetti (Fri,) studied this question.