Analysis of the exclusive final state npe$^+$e$^-$ in quasi-free np reaction
Creators: name: Adamczewski-Musch, J.
name: Arnold, O.
name: Atomssa, E. T.
name: Behnke, C.
name: Belounnas, A.
name: Belyaev, A.
name: Berger-Chen, J. C.
name: Biernat, J.
name: Blanco, A.
name: Blume, C.
name: Böhmer, M.
name: Bordalo, P.
name: Chernenko, S.
name: Chlad, L.
name: Deveaux, C.
name: Dreyer, J.
name: Dybczak, A.
name: Epple, E.
name: Fabbietti, L.
name: Fateev, O.
name: Filip, P.
name: Finocchiaro, P.
name: Fonte, P.
name: Franco, C.
name: Friese, J.
name: Fröhlich, I.
name: Galatyuk, T.
name: Garzón, J. A.
name: Gernhäuser, R.
name: Golubeva, M.
name: Guber, F.
name: Gumberidze, M.
name: Harabasz, S.
name: Heinz, T.
name: Hennino, T.
name: Hlavac, S.
name: Höhne, C.
name: Holzmann, R.
name: Ierusalimov, A.
name: Ivashkin, A.
name: Kämpfer, B.
name: Karavicheva, T.
name: Kardan, B.
name: Koenig, I.
name: Koenig, W.
name: Kolb, B. W.
name: Korcyl, G.
name: Kornakov, G.
name: Kotte, R.
name: Kühn, W.
name: Kugler, A.
name: Kunz, T.
name: Kurepin, A.
name: Kurilkin, A.
name: Kurilkin, P.
name: Ladygin, V.
name: Lalik, R.
name: Lapidus, K.
name: Lebedev, A.
name: Liu, T.
name: Lopes, L.
name: Lorenz, M.
name: Mahmoud, T.
name: Maier, L.
name: Mangiarotti, A.
name: Markert, J.
name: Maurus, S.
name: Metag, V.
name: Michel, J.
name: Morinière, E.
name: Mihaylov, D. M.
name: Morozov, S.
name: Müntz, C.
name: Münzer, R.
name: Naumann, L.
name: Nowakowski, K. N.
name: Palka, M.
name: Parpottas, Y.
name: Pechenov, V.
name: Pechenova, O.
name: Petukhov, O.
name: Pietraszko, J.
name: Przygoda, W.
name: Ramos, S.
name: Ramstein, B.
name: Reshetin, A.
name: Rodriguez-Ramos, P.
name: Rosier, P.
name: Rost, A.
name: Sadovsky, A.
name: Salabura, P.
name: Scheib, T.
name: Schuldes, H.
name: Schwab, E.
name: Scozzi, F.
name: Seck, F.
name: Sellheim, P.
name: Siebenson, J.
name: Silva, L.
name: Sobolev, Yu. G.
name: Spataro, S.
name: Ströbele, H.
name: Stroth, J.
name: Strzempek, P.
name: Sturm, C.
name: Svoboda, O.
name: Tlusty, P.
name: Traxler, M.
name: Tsertos, H.
name: Usenko, E.
name: Wagner, V.
name: Wendisch, C.
name: Wiebusch, M. G.
name: Wirth, J.
name: Zanevsky, Y.
name: Zumbruch, P.
name: Sarantsev, A. V.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Nuclear Experiment (nucl-ex)
subject: FOS: Physical sciences
subject: FOS: Physical sciences
subject: J.2

description: We report on the investigation of dielectron production in tagged quasi-free neutron-proton collisions by using a deuteron beam of kinetic energy 1.25 GeV/u inpinging on a liquid hydrogen target. Our measurements with HADES confirm a significant excess of $e^+e^-$ pairs above the $π^{0}$ mass in the exclusive channel $dp \to npe^{+}e^{-}(p_{spect})$ as compared to the exclusive channel $ppe^{+}e^{-}$ measured in proton-proton collisions at the same energy. That excess points to different bremsstrahlung production mechanisms. Two models were evaluated for the role of the charged pion exchange between nucleons and double-$Δ$ excitation combined with intermediate $ρ$-meson production. Differential cross sections as a function of the $e^+e^-$ invariant mass and of the angles of the virtual photon, proton and electrons provide valuable constraints and encourage further investigations on both experimental and theoretical side.
description: 12 pages, 7 figures