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

Agakishiev, G.; Balanda, A.; Belver, D.; Belyaev, A.; Berger Chen, J. C.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Cabanelas, P.; Chernenko, S.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gernhäuser, R.; Göbel, K.; Golubeva, M.; González Dıaz, D.; Guber, F.; Gumberidze, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kornakov, G.; Kotte, R.; Krása, A.; Krizek, F.; Krücken, R.; Kuc, H.; Kühn, W.; Kugler, A.; Kurepin, A.; Ladygin, V.; Lalik, R.; Lang, S.; Lapidus, K.; Lebedev, A.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Müntz, C.; Naumann, L.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Schmah, A.; Schwab, E.; Siebenson, J.; Sobolev, Y. u. G.; Spataro, STEFANO GIOVANNI; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Weber, M.; Wendisch, C.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.

doi:10.1140/epja/i2014-14082-1

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 -> np pi(+) and pp -> pp pi(0) as well as pp -> 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/c(2). 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 -> 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.