Temporal propagators and quasiparticles in hot QCD

We have calculated the temporal quark and gluon propagators on large (64"3 x 16) isotropic lattice and extracted the spectral function from them. Calculating the spectral function at several spatial momenta we were able to determine the dispersion relation for quarks and gluons and extract the temperature dependent quasiparticle masses. We have found that the quasiparticle masses measured in units of temperature increase substantially as the temperature is lowered from 3T_c to 1.5T_c. Our temporal propagators are quite different from those calculated within the HTL perturbation theory. We have found that in general medium effects are stronger than suggested by hard thermal loop perturbation theory. In particular, the quasiparticle masses determined by us are generally larger than those predicted by HTL perturbation theory (except for the gluon mass at 3T_c). We also see a large continuum contribution in the gluon spectral function which is absent in the HTL approximation. (orig.)Available from TIB Hannover: RA 2999(02-109) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

A lattice calculation of thermal dilepton rates

Using clover improved Wilson fermions we calculate thermal vector meson correlation functions above the deconfinement phase transition of quenched QCD. At temperatures 1.5 T_c and 3 T_c they are found to differ by less than 15% from that of a freely propagating quark anti-quark pair. This puts severe constraints on the dilepton production rate and in particular rules out a strong divergence of the dilepton rate at low energies. The vector spectral function, which has been reconstructed using the Maximum Entropy Method, yields an enhancement of the dilepton rate over the Born rate of at most a factor two in the energy interval 4<or#approx##omega#/T<or#approx#8 and suggest that the spectrum is cut-off at low energies by a thermal mass threshold of about (2 - 3) T. (orig.)Available from TIB Hannover: RA 2999(01-175) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Hadron correlators, spectral functions and thermal dilepton rates from lattice QCD

We discuss information on thermal modifications of hadron properties which can be extracted from the structure of Euclidean correlation functions of hadronic currents as well as more direct information obtained through the reconstruction of the spectral functions based on the Maximum Entropy Method. (orig.)Available from TIB Hannover: RA 2999(02-153) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman