Thermal modifications of quarkonia and heavy quark diffusion from a comparison of continuum-extrapolated lattice results to perturbative QCD

TL;DR

This study compares lattice QCD results with perturbative calculations to analyze how heavy quarkonia are modified in hot media and to estimate heavy quark diffusion coefficients, revealing different thermal behaviors for charmonium and bottomonium.

Contribution

It provides a continuum-extrapolated lattice analysis combined with perturbative spectral functions to study in-medium quarkonia modifications and heavy quark diffusion at various temperatures.

Findings

Charmonium shows no resonance peak above T_c.

Bottomonium retains a broadened resonance up to 2.25 T_c.

Charm quarks have a larger drag coefficient than bottom quarks.

Abstract

We investigate the in-medium modifications of heavy quarkonia in the vector channel and the heavy quark diffusion coefficient by comparing Euclidean correlators from the lattice to a perturbative spectral function. On the lattice side, we work with continuum extrapolated data from four different large and fine lattices with Clover-improved Wilson fermions in the quenched approximation at five temperatures (0.75, 1.1, 1.3, 1.5 and 2.25$T_c$). On the perturbative side, we use a combination of pNRQCD and vacuum asymptotics to describe the spectral function. After accounting for systematic errors, we obtain a spectral function that is suited to describe the bound state region. This spectral function describes charmonium well without a resonance peak at any of our analyzed temperatures above $T_c$, while we observe a thermally broadened resonance peak for bottomonium that is only melted at our largest temperature, $2.25T_c$. For the transport contribution we assume a Breit-Wigner shaped peak and find that the drag coefficient of charm quarks is larger than that of bottom quarks.