Quarkonium $p_{\rm T}$ spectra in heavy--ion collisions at LHC energies within a hydrodynamic core--corona framework

TL;DR

This paper models quarkonium production in heavy-ion collisions at LHC energies using an analytical hydrodynamic framework combined with a core-corona approach, successfully describing experimental spectra and yield ratios.

Contribution

It introduces a unified analytical hydrodynamic model with core-corona effects to describe quarkonium spectra in heavy-ion collisions at LHC energies.

Findings

The model reproduces charmonium and bottomonium spectra across a broad $p_{\rm T}$ range.

It successfully describes the $\\psi(2S)/J/\psi$ ratio and bottomonium yield ratios.

Deviations at high $p_{\rm T}$ suggest additional production mechanisms.

Abstract

We present a systematic study of the transverse momentum ($p_{\rm T}$) spectra of charmonium (J/$\psi$, $\psi(2S)$) and bottomonium ($\Upsilon(nS)$) states in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV within an analytical relativistic hydrodynamics framework. The medium evolution is described assuming cylindrical symmetry with boost-invariant longitudinal expansion and Hubble-like transverse flow. Quarkonium spectra are evaluated using the Cooper-Frye formalism on a constant-temperature freeze-out hypersurface, supplemented by a core--corona approach to include both thermal and non-thermal contributions. The model describes the measurements from ALICE and CMS over a broad $p_{\rm T}$ range. For charmonium, both the spectra and the $\psi(2S)$/J/$\psi$ ratio are well reproduced, while deviations at high $p_{\rm T}$ for J/$\psi$ indicate additional hard production mechanisms. In the bottomonium sector, the $\Upsilon(nS)$ spectra and their yield ratios are successfully described, consistent with the expected sequential suppression pattern. These results demonstrate that an analytical hydrodynamic approach combined with a core-corona framework provides a unified and transparent description of quarkonium production in heavy--ion collisions at LHC energies.