Static quark anti-quark free energy and the running coupling at finite temperature

TL;DR

This paper investigates the free energy of static quark-antiquark pairs in quenched QCD at finite temperature, identifying the transition between perturbative and non-perturbative regimes and discussing implications for heavy quark bound states.

Contribution

It introduces a method to determine the length scale separating perturbative and non-perturbative regimes in the QCD plasma at high temperature.

Findings

Identification of the scale separating regimes at high temperature

Discussion of ambiguities in defining couplings beyond perturbation

Non-perturbative properties near T_c relate to confinement remnants

Abstract

We analyze the free energy of a static quark anti-quark pair in quenched QCD at short and large distances. From this we deduce running couplings, g^2(r,T), and determine the length scale that separates at high temperature the short distance perturbative regime from the large distance non-perturbative regime in the QCD plasma phase. Ambiguities in the definition of a coupling beyond the perturbative regime are discussed in their relation to phenomenological considerations on heavy quark bound states in the quark gluon plasma. Our analysis suggests that it is more appropriate to characterize the non-perturbative properties of the QCD plasma phase close to T_c in terms remnants of the confinement part of the QCD force rather than a strong Coulombic force.