Valence quarks in the QCD plasma: quark number susceptibilities and screening

Abstract

We have investigated the quark sector of quenched QCD for 1.5\le T/Tc\le3 in the continuum limit, using two different lattice discretisations of quarks and extrapolating from lattice spacings between 1/4T and 1/14T. At these temperatures, the flavour off-diagonal susceptibility, chi_{ud}/T^2, is compatible with zero at each lattice spacing, and hence also in the continuum limit. In the continuum limit, the light quark susceptibilities are about 10% less than the ideal gas results even at the highest T, in agreement with hard thermal loop predictions but marginally below a resummed perturbative computation. For the mass range appropriate to the strange quark, the flavour diagonal susceptibility is significantly smaller. Our estimate of the Wroblewski parameter is compatible with observations at RHIC and SPS. The continuum limit of screening masses in all (local) quark-bilinears is very close to the ideal gas results.