Thermal QCD sum rules in the rho(0) channel revisited

From the hypothesis that at zero temperature the square root of the spectra l continuum threshold s(0) is linearly related to the QCD scale Lambda we d erive in the chiral limit and for temperatures considerably smaller than La mbda scaling relations for the vacuum parts of the Gibbs averaged scalar op erators contributing to the thermal operator product expansion of the rho ( 0) current-current correlator. The scaling with lambda drop roots(0)(T)/s(0 )(0), s(0) being the T-dependent perturbative QCD continuum threshold in th e spectral integral, is simple for renormalization group invariant operator s, and becomes nontrivial for a set of operators which mix and scale anomal ously under a change of the renormalization point. In contrast to previous works on thermal QCD sum rules with this approach the gluon condensate exhi bits a sizable T-dependence. The rho -meson mass is found to rise slowly wi th temperature which coincides with the result found by means of a PCAC and current algebra analysis of the rho (0) correlator.