Transverse Momentum Spectra of J/\psi in Heavy-Ion Collisions

TL;DR

This paper models J/ transverse momentum spectra in heavy-ion collisions at SPS and RHIC, combining primordial production with dissociation and coalescence, to explain observed suppression and regeneration patterns.

Contribution

It introduces a two-component model incorporating dissociation and coalescence, with momentum-dependent rates, to describe J/ spectra across different energies and centralities.

Findings

Fair agreement with SPS p_t spectra due to interplay of effects.

Transition from regeneration to direct production at RHIC energies.

Dominance of direct production at lower centralities.

Abstract

We investigate J/\psi transverse-momentum (p_t) distributions and their centrality dependence in heavy-ion collisions at SPS and RHIC within the framework of a two-component model, which includes (i) primordial production coupled with various phases of dissociation, (ii) statistical coalescence of c and \bar{c} quarks at the hadronization transition. The suppression of the direct component (i) is calculated by solving a transport equation for J/\psi, \chi_c and \psi' in an expanding fireball using momentum dependent dissociation rates in the Quark-Gluon Plasma (QGP). The coalescence component is inferred from a kinetic rate equation with a momentum dependence following from a blast wave approach. At SPS energies, where the direct component dominates, the interplay of Cronin effect and QGP suppression results in fair agreement with NA50 p_t spectra. At RHIC energies, the p_t spectra in central Au+Au collisions are characterized by a transition from regeneration at low p_t to direct production above. At lower centralities, the latter dominates at all p_t.