Temporal quark correlation functions are analyzed in quenched lattice QCD for two values of temperature above the critical temperature ($T_c$) for deconfinement, $T=1.5T_c$ and $3T_c$. 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 ${128}^3\times 16$. 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 quasiparticle peaks in the quark spectrum. We furthermore find evidence that the dispersion relation of the plasmino mode has a minimum at nonzero momentum even in the nonperturbative region near $T_c$. We also elaborate on the enhancement of the quark correlator near the chiral limit which is observed at $T=1.5T_c$ 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 nontrivial topology of the gauge configurations.

• Received 12 June 2012

DOI:https://doi.org/10.1103/PhysRevD.86.036006