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

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

doi:10.1140/epja/i2014-14082-1

2023 Impact factor 2.6

Hadrons and Nuclei

Open Access

Eur. Phys. J. A (2014) 50: 82
https://doi.org/10.1140/epja/i2014-14082-1

Regular Article - Experimental Physics

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

G. Agakishiev⁷, A. Balanda³, D. Belver¹⁸, A. Belyaev⁷, J. C. Berger-Chen⁹, A. Blanco², M. Böhmer¹⁰, J. L. Boyard¹⁶, P. Cabanelas¹⁸, S. Chernenko⁷, A. Dybczak³, E. Epple⁹, L. Fabbietti⁹, O. Fateev⁷, P. Finocchiaro¹, P. Fonte², J. Friese¹⁰, I. Fröhlich⁸, T. Galatyuk⁵, J. A. Garzón¹⁸, R. Gernhäuser¹⁰, K. Göbel⁸, M. Golubeva¹³, D. González-Dıaz⁵, F. Guber¹³, M. Gumberidze⁵, T. Heinz⁴, T. Hennino¹⁶, R. Holzmann⁴, A. Ierusalimov⁷, I. Iori¹², A. Ivashkin¹³, M. Jurkovic¹⁰, B. Kämpfer⁶, T. Karavicheva¹³, I. Koenig⁴, W. Koenig⁴, B. W. Kolb⁴, G. Kornakov⁵, R. Kotte⁶, A. Krása¹⁷, F. Krizek¹⁷, R. Krücken¹⁰, H. Kuc³^,16, W. Kühn¹¹, A. Kugler¹⁷, A. Kurepin¹³, V. Ladygin⁷, R. Lalik⁹, S. Lang⁴, K. Lapidus⁹, A. Lebedev¹⁴, T. Liu¹⁶, L. Lopes², M. Lorenz⁸, L. Maier¹⁰, A. Mangiarotti², J. Markert⁸, V. Metag¹¹, B. Michalska³, J. Michel⁸, C. Müntz⁸, L. Naumann⁶, Y. C. Pachmayer⁸, M. Palka³, Y. Parpottas¹⁵, V. Pechenov⁴, O. Pechenova⁸, J. Pietraszko⁴, W. Przygoda³^*, B. Ramstein¹⁶, A. Reshetin¹³, A. Rustamov⁸, A. Sadovsky¹³, P. Salabura³, A. Schmah¹, E. Schwab⁴, J. Siebenson⁹, Yu. G. Sobolev¹⁷, S. Spataro¹, B. Spruck¹¹, H. Ströbele⁸, J. Stroth⁸^,4, C. Sturm⁴, A. Tarantola⁸, K. Teilab⁸, P. Tlusty¹⁷, M. Traxler⁴, R. Trebacz³, H. Tsertos¹⁵, T. Vasiliev⁷, V. Wagner¹⁷, M. Weber¹⁰, C. Wendisch⁶, J. Wüstenfeld⁶, S. Yurevich⁴ and Y. Zanevsky⁷

¹ INFN, Laboratori Nazionali del Sud, 95125, Catania, Italy
² LIP-Laboratório de Instrumentação e Física Experimental de Partículas, 3004-516, Coimbra, Portugal
³ Smoluchowski Institute of Physics, Jagiellonian University of Cracow, 30-059, Kraków, Poland
⁴ GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291, Darmstadt, Germany
⁵ Technische Universität Darmstadt, 64289, Darmstadt, Germany
⁶ Institut für Strahlenphysik, Helmholtz-Zentrum Dresden-Rossendorf, 01314, Dresden, Germany
⁷ Joint Institute of Nuclear Research, 141980, Dubna, Russia
⁸ Institut für Kernphysik, Goethe-Universität, 60438, Frankfurt, Germany
⁹ Excellence Cluster “Origin and Structure of the Universe”, 85748, Garching, Germany
¹⁰ Physik Department E12, Technische Universität München, 85748, Garching, Germany
¹¹ II.Physikalisches Institut, Justus Liebig Universität Giessen, 35392, Giessen, Germany
¹² INFN, Sezione di Milano, 20133, Milano, Italy
¹³ Institute for Nuclear Research, Russian Academy of Science, 117312, Moscow, Russia
¹⁴ Institute of Theoretical and Experimental Physics, 117218, Moscow, Russia
¹⁵ Department of Physics, University of Cyprus, 1678, Nicosia, Cyprus
¹⁶ Institut de Physique Nucléaire (UMR 8608), CNRS/IN2P3, Université Paris Sud, F-91406, Orsay Cedex, France
¹⁷ Nuclear Physics Institute, Academy of Sciences of Czech Republic, 25068, Rez, Czech Republic
¹⁸ LabCAF. F. Física, Univ. de Santiago de Compostela, 15706, Santiago de Compostela, Spain

^* e-mail: witold.przygoda@uj.edu.pl

Received: 3 January 2014
Revised: 12 March 2014
Accepted: 25 March 2014
Published online: 9 May 2014

Abstract

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.