Quark propagator at finite temperature and finite momentum in quenched lattice QCD

Abstract

We present an analysis of the quark spectral function above and below the critical temperature for deconfinement performed at zero and nonzero momentum in quenched lattice QCD using clover improved Wilson fermions in Landau gauge. It is found that the temporal quark correlation function in the deconfined phase near the critical temperature is well reproduced by a two-pole ansatz for the spectral function. This indicates that excitation modes of the quark field have small decay rates. The bare quark mass and momentum dependence of the spectral function is analyzed with this ansatz. In the chiral limit we find that the quark spectral function has two collective modes corresponding to the normal and plasmino excitations in the high-temperature limit. Over a rather wide temperature range in the deconfined phase the pole mass of these modes at zero momentum, which corresponds to the thermal mass of the quark, is approximately proportional to temperature. With increasing bare quark masses the plasmino mode gradually disappears, and the spectral function is dominated by a single pole. We also discuss quasiparticle properties of heavy quarks in the deconfined phase. In the confined phase, it is found that the pole ansatz for the spectral function fails completely.

Phase diagram and thermal properties of strong-interaction matter

“…With T p = T c , the critical temperature for chiral symmetry restoration, then a = 0.029, b = 0.47 yield a dressed-quark thermal mass m T = 0.8 T at T = 2T c , in agreement with lQCD simulations [35].…”

“…This associates it with dynamically-driven changes in the analytic structure of QCD's propagators and vertices [50][51][52][53][54][55] that occur because both gluons and quarks acquire running mass distributions, which are large at infrared momenta. This leads to the emergence of a length-scale ς ≈ 0.5 fm, whose existence and size is evident in all continuum and lQCD studies of dressed-gluons and -quarks: ς characterises the material change in their analytic structure [6,35,56,57]. From this perspective, deconfinement occurs when ς → 0 and reflection positivity is thus recovered.…”

Gauge bosons at zero and finite temperature

“…Going into details or even listing a complete set of references just for Landau gauge is far beyond the scope of this review. It suffices to say that one can investigate from them a phletora of physical phenomena like, e. g., the dynamical generation of mass [14, 271, 272, 280, 355-358, 365, 366, 368, 369], chiral symmetry breaking and restoration at finite temperature [280,370,371], the deconfinement transition [249,[371][372][373][374], center observables like the Polyakov loop [249,375], conceptual access to the string tension [206][207][208]376], confinement of matter fields [206-208, 375, 377], color-superconducting phases at large densities [239,[378][379][380][381], the Higgs effect [25], and infrared conformality [6,26,382,383], only to mention some. However, already from the brief presentation in figure 36, it can be deduced that the presence …”

Dilepton production spectrum aboveTcwith a lattice quark propagator

“…This pole ansatz was employed motivated by the study of fermion propagator at nonzero temperature [24,25]. It has been shown [21][22][23] that this simple ansatz can reproduce the quark correlator obtained on the lattice over a rather wide range of bare quark mass and momentum. It is therefore expected that the obtained quark propagator well grasps the gist of the nonperturbative nature of the quark propagator.…”

“…Recently, an analysis of the nonperturbative quark propagator above T c was performed on the lattice in the quenched approximation in Landau gauge [21][22][23]. In this series of analyses, the quark propagator was analyzed with the two-pole ansatz for the real-time propagator in order to carry out the analytic continuation.…”