Open Access

Geydar Agakishiev, Héctor Álvarez-Pol, Andrzej Balanda, Roberto Bassini, Michael Böhmer, Helmut Bokemeyer, Jean-Louis Boyard, Pablo Cabanelas Eiras, Sergey Chernenko, Tassilo Christ, Marco Giovanni Maria Destefanis, Frank Dohrmann, Adrian Dybczak, Thomas Eberl, Laura Fabbietti, Oleg Fateev, Paolo Finocchiaro, Jürgen Friese, Ingo Fröhlich, Tetyana Galatyuk, Juan A. Garzón, Roman Gernhäuser, Camilla Gilardi, Marina Golubeva, Diégo González-Díaz, Fedor Guber, Malgorzata Gumberidze, Thierry Hennino, Romain Holzmann, Alexander P. Ierusalimov, Ileana Iori, Alexander Ivashkin, Martin Jurkovič, Burkhard Kämpfer, Kalliopi Kanaki, Tatiana Karavicheva, Ilse Koenig, Wolfgang Koenig, Burkhard W. Kolb, Roland Kotte, Anna Kozuch, Filip Krizek, Wolfgang Kühn, Andrej Kugler, Alexei Kurepin, Simon Martin Lang, Kirill Lapidus, T. Liu, Ludwig W. Maier, Jochen Markert, Volker Metag, Beata Michalska, Emilie Morinière, Jehad Mousa, Mathias Münch, Christian Münch, Lothar Naumann, Jacek Tomasz Otwinowski, Yvonne C. Pachmayer, Vladimir Pechenov, Olga Pechenova, Tiago Pérez Cavalcanti, Jerzy Pietraszko, Vladimir Pospısil, Witold Przygoda, Béatrice Ramstein, Andrey Reshetin, M. Roy-Stephan, Anar Rustamov, Alexander Sadovsky, Benjamin Sailer, Piotr Salabura, M. Sánchez, Alexander Schmah, Erwin Schwab, Yuri G. Sobolev, Stefano Spataro, Björn Spruck, Herbert Ströbele, Joachim Stroth, Christian Thomas Sturm, Attilio Tarantola Peloni, Khaled Teilab, Pavel Tlustý, Alberica Toia, Michael Traxler, Radoslaw Trebacz, Haralabos Tsertos, Vladimir Wagner, Marcin Wisniowski, Tomasz Wojcik, Jörn Wüstenfeld, Sergey Yurevich, Yuri V. Zanevsky, Peter W. Zumbruch

• We present measurements of exclusive ensuremathπ+,0 and η production in pp reactions at 1.25GeV and 2.2GeV beam kinetic energy in hadron and dielectron channels. In the case of π+ and π0 , high-statistics invariant-mass and angular distributions are obtained within the HADES acceptance as well as acceptance-corrected distributions, which are compared to a resonance model. The sensitivity of the data to the yield and production angular distribution of Δ (1232) and higher-lying baryon resonances is shown, and an improved parameterization is proposed. The extracted cross-sections are of special interest in the case of pp → pp η , since controversial data exist at 2.0GeV; we find \ensuremathσ=0.142±0.022 mb. Using the dielectron channels, the π0 and η Dalitz decay signals are reconstructed with yields fully consistent with the hadronic channels. The electron invariant masses and acceptance-corrected helicity angle distributions are found in good agreement with model predictions.