J/Psi production in heavy ion collisions and gluon saturation

TL;DR

The paper develops a saturation-based framework for J/psi production in high-energy heavy ion collisions, integrating the Color Glass Condensate/KLN approach with a dipole description of ccbar dynamics. It identifies a dominant higher-twist production mechanism in hadron–nucleus and nucleus–nucleus interactions and shows that gluon saturation shapes the rapidity distributions, yielding a more midrapidity-centered profile in AA than in pp. Numerical results for Au–Au at RHIC energies indicate that cold nuclear matter effects account for a substantial portion of the observed J/psi suppression, though final-state hot medium effects may still contribute. Overall, the work highlights the importance of saturation physics in interpreting J/psi yields and provides a quantitative framework for disentangling cold and hot nuclear matter contributions.

Abstract

We calculate the inclusive J/Psi production in heavy ion collisions including the effects of gluon saturation in the wave functions of the colliding nuclei. We argue that the dominant production mechanism in proton--nucleus and nucleus--nucleus collisions for heavy nuclei is different from the one in hadron-hadron interactions. We find that the rapidity distribution of primary J/Psi production is more peaked around midrapidity than the analogous distribution in elementary pp collisions. We discuss the consequences of this fact on the experimentally observed J/Psi suppression in Au-Au collisions at RHIC energies.

Figures (6)

• Figure 1: The main diagrams for the process of inclusive $c\bar{c}$ production with fixed relative momentum in nucleus-nucleus collisions (see Appendix).
• Figure 2: Rapidity dependence of the ratio $R(Y)=\frac{\frac{d \sigma}{d Y}(Y)}{\frac{d \sigma}{d Y}(Y=0)}$ for the gold-gold collision at RHIC. For the saturation momenta the KLN expression was used.
• Figure 3: $J/\psi$ rapidity distribution in Au-Au collisions for different centrality cuts. Experimental data from Adare:2006ns.
• Figure 4: Ratios of $J/\psi$ rapidity distribution in $Au-Au$ collisions: Experimental data Adare:2006ns divided by theoretical our results.
• Figure 5: Nuclear modification factor for $J/\psi$ production in heavy ion collisions for different rapidities.