Thermal mass and dispersion relations of quarks in the deconfined phase of quenched QCD

TL;DR

This study investigates quark spectral functions in quenched lattice QCD above the deconfinement temperature, revealing quasi-particle peaks and non-trivial dispersion relations, including a plasmino mode minimum at non-zero momentum.

Contribution

It provides the first detailed non-perturbative analysis of quark dispersion relations and spectral functions at high temperatures in quenched QCD using a two-pole ansatz.

Findings

Evidence of quasi-particle peaks in quark spectra.

Dispersion relation of the plasmino mode has a minimum at non-zero momentum.

Enhanced quark correlator near the chiral limit linked to topological zero modes.

Abstract

Temporal quark correlation functions are analyzed in quenched lattice QCD for two values of temperature above the critical temperature (Tc) for deconfinement, T=1.5Tc and 3Tc. A two-pole ansatz for the quark spectral function is used to determine the bare quark mass and the momentum dependence of excitation spectra on large lattices of size up to 128^3x16. The dependence of the quark correlator on these parameters as well as the finite volume dependence of the excitation energies are analyzed in detail in order to examine the reliability of our analysis. Our results suggest the existence of quasi-particle peaks in the quark spectrum. We furthermore find evidence that the dispersion relation of the plasmino mode has a minimum at non-zero momentum even in the non-perturbative region near Tc. We also elaborate on the enhancement of the quark correlator near the chiral limit which is observed at T=1.5Tc on about half of the gauge configurations. We attribute this to the presence of near zero-modes of the fermion matrix that are associated with non-trivial topology of the gauge configurations.