Dielectron measurements with the HADES at GSI

Abstract

In this work we present the dielectron analysis of 4.5 billion Ag+Ag collisions ((0−40)% centrality) at a center-of-mass energy of √sNN = 2.55 GeV measured with HADES. The obtained dielectron signal spectrum is compared to simulated hadronic cocktail and nucleon-nucleon reference spectra revealing a strong contribution from the hot and dense phases. The average temperature of the collision system can be extracted from the slope of the in-medium contribution. In a momentum differential analysis we observe modifications of the dielectron signal shape in the ω−ρ invariant mass region. Furthermore we compare the results to previous measurements in Au+Au collisions at slightly lower energy. The suggested modifications of the ρ spectral function is further studied within the HADES pion-beam program. Here, we present recently published results on the electromagnetic and hadronic coupling of baryonic resonances to the ρ − N final state.