Application of fixed scale approach to static quark free energies in quenched and 2+1 flavor lattice QCD with improved Wilson quark action

TL;DR

This study investigates static quark free energies and Debye screening in quark-gluon plasma using lattice QCD with improved Wilson quarks, demonstrating temperature-dependent screening effects and the validity of the fixed-scale approach.

Contribution

It applies the fixed-scale approach to analyze static quark free energies in 2+1 flavor lattice QCD with improved Wilson quarks, revealing temperature effects on screening and short-distance physics.

Findings

Short-distance free energies match zero-temperature potentials.

Long-distance free energies show full screening, approaching twice the single-quark free energy.

Screened Coulomb form describes screening at high temperatures.

Abstract

Free energies between static quarks and Debye screening masses in the quark-gluon plasma are studied on the basis of Polyakov-line correlations in lattice simulations of 2+1 flavors QCD with the renormalization-group improved gluon action and the $O(a)$-improved Wilson quark action. We perform simulations at $m_{\rm PS}/m_{\rm V} = 0.63$ (0.74) for light (strange) flavors with lattice sizes of $32^3 \times N_t$ with $N_t=4$--12. We adopt the fixed-scale approach, where temperature can be varied without changing the spatial volume and renormalization factor. We find that, at short distance, the free energies of static quarks in color-singlet channel converge to the static-quark potential evaluated from the Wilson-loop at zero-temperature, in accordance with the expected insensitivity of short distance physics to the temperature. At long distance, the free energies of static quarks approach to twice the single-quark free energies, implying that the interaction between static quarks is fully screened. The screening properties can be well described by the screened Coulomb form with appropriate Casimir factor at high temperature. We also discuss a limitation of the fixed-scale approach at high temperature.