Search for the kaonic bound state ppK⁻ in pp→ pK⁺Λ

The investigation of the kaon-nucleon interaction has been intensified in the last years due to new measurements of the Λ(1405) resonance and indications on the existence of the ppK⁻ bound state. Such results are heavily discussed, since they can lead to new knowledge about the $\overline{K}$-Nucleon interaction. In the last years, the reaction p+p →p+ K⁺ + Λ has been measured at the GSI Helmholtzcentre in Darmstadt with the FOPI and the HADES spectrometers at beam energies of 3.1 GeV and 3.5 GeV, respectively. New analyses methods have been developed to understand quantitatively all the processes contributing to the pK⁺Λ final state. At the FOPI experiment a set of around 1.000 events and in the HADES experiment around 22.000 events of the exclusive reaction p+p →p+ K⁺ + Λ could be extracted. These reconstructed exclusive events were analyzed within the Bonn Gatchina Partial Wave Analysis (BG-PWA) framework, which provides a coherent description of the data including several resonant and non-resonant production channels. The results have shown that the inclusion of interferences between different channels has to be considered in the analysis. Based on the description of the data with the Partial Wave Analysis an upper limit on the cross-section for the production of the ppK⁻ could be determined.