A MESON-EXCHANGE MODEL FOR THE ANTIHYPERON HYPERON PRODUCTION

A meson-exchange model for strangeness production processes ppBAR --> YYBAR (Y = LAMBDA, SIGMA) is presented, which is based on a full coupled-channel treatment. The transition interactions are given by K- and K*-meson exchange. The elastic part of the ppBAR and YYBAR interactions has been derived from a one-boson-exchange version of the Bonn NN potential and a corresponding extension to the hyperon-nucleon case whereas the annihilation part is taken into account by introducing phenomenological optical potentials. Results for cross sections, polarizations, depolarization and spin correlation parameters are presented for the reactions ppBAR --> LAMBDASIGMA0BAR, SIGMA0LAMBDABAR as well as ppBAR --> SIGMABAR +/- SIGMA +/-, SIGMA0SIGMA0BAR. As in ppBAR --> LAMBDALAMBDABAR, tensor and spin-triplet dominance is realized in ppBAR --> SIGMASIGMABAR but is somewhat reduced in ppBAR --> LAMBDASIGMA0BAR, SIGMA0LAMBDABAR. Although SIGMA-SIGMA-BAR cannot be reached from ppBAR by a one step transition the corresponding cross section is only slightly smaller than that for SIGMA+SIGMA+BAR. For ppBAR --> LAMBDASIGMA0BAR, SIGMA0LAMBDABAR, the results are compared to those derived from different transition interactions based on (i) K-exchange only and (ii) the constituent quark model (S-3(1) version). Predictions are made for the YYBAR --> YYBAR cross sections.