Dilepton analysis in the HADES spectrometer for C+C at 2 A GeV

The high-acceptance dielectron spectrometer (HADES) has become operational at GSI Darmstadt. The primary physics programme is to study in-medium changes of light vector mesons via their e+e− decays. The methods of dilepton signal reconstruction in the HADES spectrometer and preliminary dilepton spectra for C+C reactions at 2 A GeV are presented. In the signal reconstruction, particularly important is the reduction of the huge combinatorial background arising from e+e− combinations of leptons from gamma conversion in materials with other leptons in the collision. The purity of the dilepton signal is determined by using GEANT simulations with the full HADES geometry and a realistic detector response.