$\Upsilon(1S)$ transverse momentum spectra through dissociation and regeneration in heavy ion collisions

TL;DR

This paper models the transverse momentum spectra of $
$ in heavy ion collisions by incorporating dissociation and regeneration effects, explaining experimental data through a combined theoretical approach.

Contribution

It introduces a unified framework using pNRQCD and Boltzmann equations to analyze quarkonium suppression and regeneration across different temperatures and momenta.

Findings

High-$p_T$ $
$ $R_{AA}$ influenced by regeneration effects.

CMS data's $p_T$ independence explained by dissociation-regeneration interplay.

Calculated $
$ $v_2$ consistent with experimental limits.

Abstract

We calculate the transition between a quarkonium state and an unbound heavy quark-antiquark pair through gluo-dissociation and inelastic parton scattering using a partonic picture that interpolates between the formal limits based on potential nonrelativistic QCD (pNRQCD) at different temperatures. While the thermal width increases with momentum and temperature, the quarkonium regeneration is affected by the heavy quark distribution function which depends on the diffusion constant. By solving the Boltzmann equation with the dissociation and regeneration terms, we investigate the medium modifications of quarkonium momentum spectra. Our numerical results indicate that the $\Upsilon(1S)$ $R_{AA}$ at high transverse momentum are influenced by the regeneration effects depending on the heavy quark diffusion. In this picture, the published CMS data that show an almost transverse momentum independence can be explained by the interplay between the suppression by dissociation and enhancement by regeneration at low and high transverse momenta, respectively. With the same input, we also calculate the transverse momentum dependence of the $\Upsilon(1S)$ $v_2$ and show that it lies within the limits of the available data.