Spectral functions of heavy quarkonia in a bulk-viscous quark gluon plasma

TL;DR

This paper investigates how bulk viscosity in a quark-gluon plasma affects heavy quarkonia properties, including spectral functions and observable ratios, providing insights into the medium's non-equilibrium effects.

Contribution

It introduces a method to incorporate bulk viscous effects into the dielectric permittivity and potential calculations for heavy quarkonia in a quark-gluon plasma.

Findings

Bulk viscous effects modify binding energies and thermal widths of quarkonia.

Different sensitivities of quarkonium states to bulk viscosity could aid in critical point searches.

The study links medium properties to observable quantities like $R_{AA}$ and quarkonium ratios.

Abstract

We study the properties of quarkonia inside a bulk-viscous quark gluon plasma. The non-equilibrium nature of the medium is encoded in the deformed distribution functions of thermal quarks and gluons, with which we compute the dielectric permittivity within the hard thermal loop approximation at one-loop. The modified dielectric permittivity is used to calculate the in-medium heavy quark potential, and using the potential we compute spectral functions, which reflect the physical properties of heavy quarkonia. We discuss how the bulk viscous effect influences quantities such as binding energies and thermal widths. Based on those properties, we discuss the implications of the bulk viscous effect on the physical observables such as $ \psi' $ to $ J/\psi $ ratio and the nuclear modification factor, $R_{AA}$. In particular, we argue that the nuclear modification factors of excited and ground states show different sensitivities to the bulk viscous nature of a plasma, which is potentially useful for the critical point search.