Workshop for young scientists with research interests focused on physics at FAIR

One of the main physics goals of HADES is to investigate spectral modifications of light vector mesons in strongly interacting matter via their dilepton (e+e−) decay channel. Theoretical models predict such modifications due to strong meson-baryon resonance coupling which can be also probed in elementary collisions. In 2007 electron-positron pair production has been measured in p+p reactions with beam kinetic energy of 3.5 GeV. One of the basic observables in this measurement is inclusive e+ e− mass distribution. The expected e+e− production channels are given by Dalitz decays of π0, η, ω mesons and ∆(1232) resonance. Indeed, the experimental data can be described by simulation of the aforementioned components, everywhere but not in the mass region below vector meson pole (M_inv ∈ (0.5 − 0.7)). We present analysis results of the exclusive channels ppπ0, pnπ+, ppe+e−, which might indicate contributions of higher lying resonances. In order to estimate production cross sections of the baryonic resonances for hadronic channels, the results have been compared to Monte-Carlo calculations based on the resonance model assuming incoherent sum of various four stars resonances. To convert obtained resonances cross sections into e+ e− yield, two models of dΓ(R→pe+ e−)/dM(e+e-) are applied in the simulation.