Non-equilibrium charmonium regeneration in strongly coupled quark-gluon plasma

TL;DR

This paper develops a semi-classical transport model for charmonium regeneration in quark-gluon plasma, incorporating nonperturbative charm-medium interactions and non-equilibrium effects, to better match experimental data from heavy-ion collisions.

Contribution

It introduces a unified transport framework that combines nonperturbative charm interactions with dynamical charm quark spectra for improved quarkonium regeneration modeling.

Findings

Large K-factor (~5) needed for accurate J/ψ yield reproduction

Nonperturbative interactions are essential for matching experimental data

Framework links open and hidden heavy-flavor observables

Abstract

The evaluation of quarkonium regeneration in ultrarelativistic heavy-ion collisions (URHICs) requires the knowledge of the heavy-quark phase space distributions in the expanding quark-gluon plasma (QGP) fireball. We employ a semi-classical charmonium transport approach where regeneration processes explicitly account for the time-dependent spectra of charm quarks via Langevin simulations of their diffusion. The inelastic charmonium rates and charm-quark transport coefficients are computed from the same charm-medium interaction. The latter is modeled by perturbative rates, augmented with a $K$-factor to represent nonperturbative interaction strength and interference effect. Using central 5.02~TeV Pb-Pb collisions as a test case we find that a good description of the measured $J/\psi$ yield and its transverse-momentum dependence can be achieved if a large $K\gtrsim5$ is employed while smaller values lead to marked discrepancies. This is in line with open-charm phenomenology in URHICs, where nonperturbative interactions of similar strength are required. Our approach establishes a common transport framework for a microscopic description of open and hidden heavy-flavor (HF) observables that incorporates both nonperturbative and non-equilibrium effects, and thus enhances the mutual constraints from experiment on the extraction of transport properties of the QGP.