Evaluation of QCD sum rules for light vector mesons at finite density and temperature

QCD sum rules are evaluated at finite nucleon densities and temperatures to determine the change of mass parameters for the lightest vector mesons rho, omega and phi in a strongly interacting medium. For conditions relevant for the starting experiments at HADES we find that the in-medium mass shifts of the rho- and omega-mesons are governed, within the Borel QCD sum rule approach, by the density and temperature dependence of the four-quark condensate. In particular, the variation of the strength of the density dependence of the four-quark condensate reflects directly the decreasing mass of the rho-meson and can lead to a change of the sign of the omega-meson mass shift as a function of the density. In contrast, the in-medium mass of the phi-meson is directly related to the chiral strange quark condensate which seems correspondingly accessible.