Unraveling Gluon Jet Quenching through $J/\psi$ Production in Heavy-Ion Collisions

TL;DR

This paper demonstrates that high transverse momentum $J/\psi$ production is a sensitive probe of gluon jet quenching in quark-gluon plasma, providing new insights into gluon energy loss through combined theoretical modeling and data analysis.

Contribution

It introduces a novel method to isolate gluon jet quenching effects using $J/\psi$ production and quantitatively extracts gluon energy loss in the quark-gluon plasma.

Findings

Gluon-dominance in high $p_T$ $J/\psi$ production established in proton-proton collisions.

Gluon jet quenching identified as the main cause of high $p_T$ $J/\psi$ suppression.

First quantitative extraction of gluon energy loss distribution in quark-gluon plasma.

Abstract

Jet quenching has long been regarded as one of the key signatures for the formation of quark-gluon plasma in heavy-ion collisions. Despite significant efforts, the separate identification of quark and gluon jet quenching has remained as a challenge. Here we show that $J/\psi$ in high transverse momentum ($p_\text{T}$) region provides a uniquely sensitive probe of in-medium gluon energy loss since its production at high $p_\text{T}$ is particularly dominated by gluon fragmentation. Such gluon-dominance is first demonstrated for the baseline of proton-proton collisions within the framework of leading power NRQCD factorization formalism. We then use the linear Boltzmann transport model combined with hydrodynamics for the simulation of jet-medium interaction in nucleus-nucleus collisions. The satisfactory description of experimental data on both nuclear modification factor $R_{\text{AA}}$ and elliptic flow $v_2$ reveals, for the first time, that the gluon jet quenching is the driving force for high $p_\text{T}$ $J/\psi$ suppression. This novel finding is further confirmed by the data-driven Bayesian analyses of relevant experimental measurements, from which we also obtain the first quantitative extraction of the gluon energy loss distribution in the quark-gluon plasma.