Studying hadron properties in baryonic matter with HADES

The HADES spectrometer installed at GSI Darmstadt is a second generation experiment to study the production of lepton pairs from proton, pion and nucleus induced reactions at the SIS/BEVALAC energy regime. The HADES study of the light C+C system at 1 and 2 AGeV confirms former findings of the DLS collaboration. Further studies of the reactions p+p and d+p allowed to reveal contributions to the above mentioned data of di-leptons produced during first chance collision. Finally, the results of the study of the heavier system Ar+KCl indicates a possible nonlinear dependence of the observed excess over the known long lived sources of di-leptons on the number of participants.