Baryon resonance production and dielectron decays in proton-proton collisions at 3.5 GeV

We report on baryon resonance production and decay in proton-proton collisions at a kinetic energy of 3.5 GeV based on data measured with HADES. The exclusive channels \( pp \rightarrow np\pi^{+}\) and \( pp\rightarrow pp\pi^{0}\) as well as \( pp\rightarrow ppe^{+}e^{-}\) are studied simultaneously for the first time. The invariant masses and angular distributions of the pion-nucleon systems were studied and compared to simulations based on a resonance model ansatz assuming saturation of the pion production by an incoherent sum of baryonic resonances (R with masses < 2 GeV/c2. A very good description of the one-pion production is achieved allowing for an estimate of individual baryon resonance production cross sections which are used as input to calculate the dielectron yields from \( R\rightarrow pe^{+}e^{-}\) decays. Two models of the resonance decays into dielectrons are examined assuming a point-like \( RN\gamma^{*}\) coupling and the dominance of the \( \rho\) meson. The results of model calculations are compared to data from the exclusive \( ppe^{+}e^{-}\) channel by means of the dielectron and \( pe^{+}e^{-}\) invariant mass distributions.