QCD sum rules are evaluated at finite nucleon densities and temperatures to determine the change of mass parameters for the lightest vector mesons ρ, ω and φ in a strongly interacting medium. For conditions relevant for the starting experiments at HADES we find that the in-medium mass shifts of the ρ and ω 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 ρ meson and can lead to a change of the sign of the ω meson mass shift as a function of the density. In contrast, the in-medium mass of the φ meson is directly related to the chiral strange quark condensate which seems correspondingly accessible.

An analysis of the dilepton measurements in the reactions Pb(158 A·GeV) + Au, Pb points to a unique thermal source contributing to the invariant mass and transverse momentum spectra. Effects of the flow pattern are discussed.

The polarization of a surrounding QCD medium modifies the induced gluon radiation spectrum of a high-energy parton at small transverse momenta for a single interaction and for multiple scatterings as well. This effect is an analogue of the Ter-Mikaelian effect in QED, superimposed to the Landau-Pomeranchuk effect, however it appears in QCD in a different phase space region.

Exploiting a unique set of parton distribution functions we estimate hard processes for open charm, dilepton and mini-jet production. Assuming rapid thermalization within the mini-jet plasma we follow the evolution (expansion and chemical equilibration) of the parton matter and calculate the energy loss of charm quarks in this environment. A substantial part of charm is expected to thermalize. We try to estimate the thermalized open charm component in the final hadron spectra.