The COSY-11 collaboration has measured the total cross section for the pp --> pp eta-prime and pp --> pp eta reactions in the excess energy range from Q = 1.5 MeV to Q = 23.6 MeV and from Q = 0.5 MeV to Q = 5.4 MeV, respectively. Measurements have been performed with the total luminosity of 73 nb^(-1) for the pp --> pp eta reaction and 1360 nb^(-1) for the pp --> pp eta-prime one. Recent results are presented and discussed.
The Lambda, Sigma0 and Sigma+ hyperon production in NN collisions is studied at the COSY - 11 installation in order to investigate the production mechanism as well as to extract information about the Y-N interaction.
We report on the COSY-11 measurements of the analysing power for the p(pol)p --> ppeta reaction and interpret the results in the framework of the meson exchange models.
The open strangeness production near threshold is investigated at the internal experiment COSY-11 in different reaction channels. Recently, the main focus has been to extend measurements of the hyperon production pp->pK+Lambda/Sigma0 in different isospin channels as well as the associated strangeness production in pp->ppK+K-. The experimental technique is based on the reconstruction of the four momentum for all positively charged ejectiles. Neutrons are detected in addition using a neutral particle detector. The unregistered hyperon or meson is identified by means of the missing mass technique. The present status of the analysis for both reaction channels is presented. In case of the reaction pp->ppK+K-, very preliminary cross sections are shown.
We summarise measurements of the COSY-11 collaboration concerning the excitation functions of the near threshold pseudoscalar meson production in the proton-proton interaction. The results are discussed in the context of the meson-nucleon and hyperon-nucleon interactions. We conclude that the $eta$-proton interaction is significantly stronger than the eta-proton interaction. Similarly, we found that the hyperon Lambda interacts with the nucleon considerably stronger than the hyperon Sigma, and that the interaction of (K-)-proton is much stronger than this of the (K+)-proton.
Selected results from experiments at COSY-Juelich are presented: an attempt to measure the mass of the eta meson with high precision (ANKE facility), first steps towards the detection of rare eta decays (WASA), and several measurements of KKbar-pair production (ANKE, COSY-11, MOMO).