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Gluon saturation effects on J/Psi production in heavy ion collisions

Dmitri Kharzeev, Eugene Levin, Marzia Nardi, Kirill Tuchin

TL;DR

The paper addresses J/ψ production in high-energy heavy-ion collisions and the role of gluon saturation in cold nuclear matter. It introduces a novel, saturation-driven mechanism within the dipole framework, employing an impact-parameter dependent saturation scale Q_s and MV/Kovchegov formalisms to model multiple scatterings in nuclei. The authors derive an AA yield and R_AA that exhibit suppression and a narrower rapidity distribution, aligning with Au-Au data using a single normalization constant, and argue that cold matter effects account for a substantial portion of the observed suppression. This work highlights the need to separate cold nuclear matter contributions from hot medium (QGP) effects in interpreting J/ψ measurements and provides a predictive framework for rapidity and centrality dependence.

Abstract

We consider a novel mechanism for J/Psi production in nuclear collisions arising due to the high density of gluons. We calculate the resulting J/Psi production cross section as a function of rapidity and centrality. We evaluate the nuclear modification factor and show that the rapidity distribution of the produced J/Psi's is significantly more narrow in AA collisions due to the gluon saturation effects. Our results indicate that gluon saturation in the colliding nuclei is a significant source of J/Psi suppression that can be disentangled from the quark-gluon plasma effects.

Gluon saturation effects on J/Psi production in heavy ion collisions

TL;DR

The paper addresses J/ψ production in high-energy heavy-ion collisions and the role of gluon saturation in cold nuclear matter. It introduces a novel, saturation-driven mechanism within the dipole framework, employing an impact-parameter dependent saturation scale Q_s and MV/Kovchegov formalisms to model multiple scatterings in nuclei. The authors derive an AA yield and R_AA that exhibit suppression and a narrower rapidity distribution, aligning with Au-Au data using a single normalization constant, and argue that cold matter effects account for a substantial portion of the observed suppression. This work highlights the need to separate cold nuclear matter contributions from hot medium (QGP) effects in interpreting J/ψ measurements and provides a predictive framework for rapidity and centrality dependence.

Abstract

We consider a novel mechanism for J/Psi production in nuclear collisions arising due to the high density of gluons. We calculate the resulting J/Psi production cross section as a function of rapidity and centrality. We evaluate the nuclear modification factor and show that the rapidity distribution of the produced J/Psi's is significantly more narrow in AA collisions due to the gluon saturation effects. Our results indicate that gluon saturation in the colliding nuclei is a significant source of J/Psi suppression that can be disentangled from the quark-gluon plasma effects.

Paper Structure

This paper contains 3 sections, 7 equations, 2 figures.

Table of Contents

  1. Introduction
  2. New mechanism of $J/\Psi$ production
  3. Conclusions

Figures (2)

  • Figure 1: The process of inclusive J/$\Psi$ production in hadron-hadron (Fig. \ref{['psi1']}-A) and in hadron-nucleus collisions (Fig. \ref{['psi1']}-B).
  • Figure 2: (a) $J/\psi$ rapidity distribution in Au-Au collisions for different centrality cuts. (b) Nuclear modification factor for $J/\Psi$ production in heavy-ion collisions for different rapidities. Experimental data from Adare:2006ns.