Thermal dilepton rate and electrical conductivity: An analysis of vector current correlation functions in quenched lattice QCD

TL;DR

This study uses quenched lattice QCD to precisely calculate vector current correlation functions at high temperature, providing insights into electrical conductivity and dilepton production in the quark-gluon plasma.

Contribution

It presents the first continuum-extrapolated vector correlation functions at T=1.45 Tc with high accuracy, constraining the spectral function and related transport coefficients.

Findings

Vector correlator deviates less than 9% from free theory.

Second thermal moment differs less than 7% from free value.

Results inform electrical conductivity and dilepton rate estimates.

Abstract

We calculate the vector current correlation function for light valence quarks in the deconfined phase of QCD. The calculations have been performed in quenched lattice QCD at T=1.45 Tc for four values of the lattice cut-off on lattices up to size 128^3x48. This allows to perform a continuum extrapolation of the correlation function in the Euclidean time interval tau*T -in [0.2, 0.5], which extends to the largest temporal separations possible at finite temperature, to better than 1% accuracy. In this interval, at the value of the temperature investigated, we find that the vector correlation function never deviates from the free correlator for massless quarks by more than 9%. We also determine the first two non-vanishing thermal moments of the vector meson spectral function. The second thermal moment deviates by less than 7% from the free value. With these constraints, we then proceed to extract information on the spectral representation of the vector correlator and discuss resulting consequences for the electrical conductivity and the thermal dilepton rate in the plasma phase.