Study from threshold to high momenta of the [formula omitted] reaction

Abstract

A semi-phenomenological model using the distorted-wave Born approximation method that incorporates the K-meson exchange is constructed for the p p → ΛΛ 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 p p interaction is based on the Paris potential. The unknown Λ Λ 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 2π exchange one, were added to the very short-range Λ Λ 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 p p annihilation is realized mainly in a Λ Λ triplet state. This can be attributed to the strong tensor force of the kaon exchange. The role of the K ∗ exchange is briefly discussed.