Open Access

Geydar Agakishiev, Oliver Werner Arnold, D. Belver, A. Belyaev, Jia-Chii Berger-Chen, Alberto Blanco, Michael Böhmer, J.L. Boyard, P. Cabanelas, S. Chernenko, A. Dybczak, Eliane Epple, Laura Fabbietti, Oleg Fateev, Paolo Finocchiaro, Paulo Fonte, J. Friese, I. Fröhlich, Tetyana Galatyuk, J.A. Garzón, Roman Gernhäuser, Kathrin Göbel, Marina Golubeva, D. González-Díaz, Fedor Guber, Malgorzata Gumberidze, T. Heinz, T. Hennino, R. Holzmann, Alexander P. Ierusalimov, I. Iori, Ivashkin Ivashkin, M. Jurkovic, B. Kämpfer, Tatiana L. Karavicheva, I. Koenig, W. Koenig, B.W. Kolb, G. Kornakov, R. Kotte, A. Krása, Filip Krizek, R. Krücken, H. Kuc, W. Kühn, Andrej Kugler, Tobias Kunz, Alexander Kurepin, Vladimir P. Ladygin, Rafał Tomasz Lalik, Kirill Lapidus, Alexei Lebedev, L. Lopes, M. Lorenz, L. Maier, Alessio Mangiarotti, Jochen Markert, Volker Metag, J. Michel, Christian Müntz, Robert Helmut Münzer, L. Naumann, Yvonne C. Pachmayer, Marek Palka, Y. Parpottas, Vladimir Pechenov, Olga Pechenova, Jerzy Pietraszko, Witold Przygoda, Béatrice Ramstein, Andrey Reshetin, Anar Rustamov, A. Sadovsky, Piotr Salabura, Alexander Schmah, E. Schwab, Johannes Stephan Siebenson, Yuri G. Sobolev, Stefano Spataro, Björn Spruck, Herbert Ströbele, Joachim Stroth, C. Sturm, A. Tarantola, K. Teilab, Pavel Tlustý, Michael Traxler, Haralabos Tsertos, T. Vasiliev, V. Wagner, Michael Weber, Christian Wendisch, Jörn Wüstenfeld, S. Yurevich, Y. Zanevsky, Andrei V. Sarantsev

• Employing the Bonn–Gatchina partial wave analysis framework (PWA), we have analyzed HADES data of the reaction p(3.5 GeV) + p → pK +Λ. This reaction might contain information about the kaonic cluster “ppK −” (with quantum numbers J P = 0− and total isospin I = 1/2) via its decay into pΛ. Due to interference effects in our coherent description of the data, a hypothetical KNN (or, specifically “ppK −”) cluster signal need not necessarily show up as a pronounced feature (e.g. a peak) in an invariant mass spectrum like pΛ. Our PWA analysis includes a variety of resonant and non-resonant intermediate states and delivers a good description of our data (various angular distributions and two-hadron invariant mass spectra) without a contribution of a KNN cluster. At a confidence level of CLs = 95% such a cluster cannot contribute more than 2–12% to the total cross section with a pK +Λ final state, which translates into a production cross-section between 0.7 μb and 4.2 μb, respectively. The range of the upper limit depends on the assumed cluster mass, width and production process.