J/Psi production in nuclear collisions: measuring the transport coefficient

TL;DR

This paper investigates the nuclear suppression of J/Psi production in heavy ion collisions, explaining the pT dependence through multiple mechanisms and estimating the medium's transport coefficient, which aligns with pQCD predictions.

Contribution

It provides a comprehensive, parameter-free model of J/Psi suppression mechanisms and extracts the transport coefficient consistent with theoretical predictions.

Findings

The transport coefficient q_0-hat is consistent with pQCD predictions.

Nuclear effects include hot medium attenuation, shadowing, and the Cronin effect.

The model explains the pT dependence of J/Psi suppression without free parameters.

Abstract

The observed pT-dependence of nuclear effects for J/Psi produced in heavy ion collisions at RHIC might look puzzling, since the nuclear suppression seems to fade at large pT. We explain this by the interplay of three mechanisms: (i) attenuation of J/Psi in the hot medium created in the nuclear collision; (ii) initial state shadowing of charmed quarks and attenuation of a c-cbar dipole propagating through the colliding nuclei; (iii) a strong Cronin effect for J/Psi caused by saturation of gluons in the colliding nuclei. All three effects are well under control and calculated in a parameter free way, except for the transport coefficient q_0-hat characterizing the medium. This is adjusted to the J/Psi data and found to be in good agreement with the pQCD prediction, but more than an order of magnitude smaller than what was extracted from jet quenching data within the energy loss scenario.