Eur. Phys. J. A (2012) 48: 64
https://doi.org/10.1140/epja/i2012-12064-y

Regular Article - Experimental Physics

Inclusive dielectron spectra in p+p collisions at 3.5 GeV kinetic beam energy

¹ Istituto Nazionale di Fisica Nucleare, 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 Institut für Strahlenphysik, Helmholtz-Zentrum Dresden-Rossendorf, 01314, Dresden, Germany
⁶ Joint Institute of Nuclear Research, 141980, Dubna, Russia
⁷ Institut für Kernphysik, Goethe-Universität, 60438, Frankfurt, Germany
⁸ Excellence Cluster “Origin and Structure of the Universe”, 85748, Garching, Germany
⁹ Physik Department E12, Technische Universität München, 85748, Garching, Germany
¹⁰ II.Physikalisches Institut, Justus Liebig Universität Giessen, 35392, Giessen, Germany
¹¹ Istituto Nazionale di Fisica Nucleare, Sezione di Milano, 20133, Milano, Italy
¹² Institute for Nuclear Research, Russian Academy of Science, 117312, Moscow, Russia
¹³ Frederick University, 1036, Nicosia, Cyprus
¹⁴ Department of Physics, University of Cyprus, 1678, Nicosia, Cyprus
¹⁵ Institut de Physique Nucléaire (UMR 8608), CNRS/IN2P3, Université Paris Sud, F-91406, Orsay Cedex, France
¹⁶ Nuclear Physics Institute, Academy of Sciences of Czech Republic, 25068, Rez, Czech Republic
¹⁷ Departamento de Física de Partículas, Univ. de Santiago de Compostela, 15706, Santiago de Compostela, Spain

^* e-mail: Rustamov@Physik.uni-frankfurt.de

Received: 18 December 2011
Accepted: 23 March 2012
Published online: 11 May 2012

Abstract

We present the inclusive invariant mass, transverse momentum and rapidity distributions of dielectrons (e⁺e^- pairs) in p+p interactions at 3.5GeV beam kinetic energy. In the vector meson mass region, a distinct peak corresponding to direct ω decays is reconstructed with a 2% mass resolution. The data is compared to predictions from three model calculations. Due to the large acceptance of the HADES apparatus for e⁺e^- invariant masses above 0.2 GeV/c ² and for transverse pair momenta p _t < 1 GeV/c, acceptance corrections are, to a large extent, model independent. This allows us to extract from dielectron data for the first time at this energy the inclusive production cross-sections for light vector mesons. Inclusive production cross-sections for π⁰ and η mesons are also reported. The obtained results will serve as an important reference for the study of vector meson production in proton-nucleus and heavy-ion collisions. Furthermore, using this data, an improved value for the upper bound of the branching ratio for direct η decays into the electron-positron channel is obtained.