STUDY FROM THRESHOLD TO HIGH MOMENTA OF THE PBARP-]LAMBDA-BAR-LAMBDA REACTION

A semi-phenomenological model using the distorted-wave Born approximation method that incorporates the K-meson exchange is constructed for the ppBAR --> LAMBDA-LAMBDABAR reaction. This diagram alone reproduces reasonably well all the available experimental data over a wide range of energies. This is mainly due to the strong annihilation in the distortions both in the initial and final states. The ppBAR interaction is based on the Paris potential. The unknown LAMBDA-LAMBDABAR interaction is built from the Paris potential and from the fit to the data. In order to achieve a good fit, a 2K-exchange box diagram and, at high momenta, a 2-pi exchange one, were added to the very short-range LAMBDA-LAMBDABAR annihilation force. The explicit energy dependence in all our imaginary potentials is found to be crucial in the whole fit. As in results from similar models a rather strong P-wave contribution is found near threshold. In agreement with the spin-correlation measurements done so far, the strangeness production from ppBAR annihilation is realized mainly in a LAMBDA-LAMBDABAR triplet state. This can be attributed to the strong tensor force of the kaon exchange. The role of the K* exchange is briefly discussed.