Δ(1232) Dalitz decay in proton-proton collisions at T=1.25 GeV measured with HADES at GSI

Adamczewski-Musch, J.; Arnold, O.; Atomssa, E. T.; Behnke, C.; Belounnas, A.; Belyaev, A.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Bohmer, M.; Bordalo, P.; Chernenko, S.; Chlad, L.; Deveaux, C.; Dreyer, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Filip, P.; Finocchiaro, P.; Fonte, P.; Franco, C.; Friese, J.; Frohlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhauser, R.; Golubeva, M.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hlavac, S.; Hohne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Kampfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Kuhn, W.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Liu, T.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Mangiarotti, A.; Markert, J.; Maurus, S.; Metag, V.; Michel, J.; Moriniere, E.; Mihaylov, D. M.; Morozov, S.; Muntz, C.; Munzer, R.; Naumann, L.; Nowakowski, K.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petousis, V.; Petukhov, O.; Pietraszko, J.; Przygoda, W.; Ramos, S.; Ramstein, B.; Reshetin, A.; Rodriguez-Ramos, P.; Rosier, P.; Rost, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataro, S.; Strobele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Tlusty, P.; Traxler, M.; Tsertos, H.; Usenko, E.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wirth, J.; Zanevsky, Y.; Zumbruch, P.; Sarantsev, A. V.

doi:10.1103/PhysRevC.95.065205

We report on the investigation of Δ(1232) production and decay in proton-proton collisions at a kinetic energy of 1.25 GeV measured with HADES. Exclusive dilepton decay channels ppe+e- and ppe+e-γ have been studied and compared with the partial-wave analysis of the hadronic ppπ0 channel. They allow to access both Δ+→pπ0(e+e-γ) and Δ+→pe+e- Dalitz decay channels. The perfect reconstruction of the well-known π0 Dalitz decay serves as a proof of the consistency of the analysis. The Δ Dalitz decay is identified for the first time and the sensitivity to N-Δ transition form factors is tested. The Δ(1232) Dalitz decay branching ratio is also determined for the first time; our result is (4.19 ± 0.62 syst. ± 0.34 stat.) ×10-5, albeit with some model dependence.