THE JULICH HYPERON-NUCLEON INTERACTION MODELS

Hyperon-nucleon interaction models (A, B), which have been developed in the meson-exchange framework by the Julich group, are reviewed, with some emphasis on characteristic conceptual differences compared to corresponding interactions constructed by the Nijmegen group. We report on two new versions A and B in which the explicit energy-dependence of the original models A and B is removed in order to simplify application in nuclear structure calculations. As a byproduct of our analysis we find that the resulting SU(3)-parameters like F/(F + D) ratios do depend on the specific model used an on approximations applied. While all models provide a reasonable description of the scarce cross-section data, sizeable differences occur in the, so far unmeasured, spin observables, especially between our models and the Nijmegen soft-core model NSC. This demonstrates clearly that a measurement of such observables can easily discriminate between present models and thus shed some light on various aspects of the hyperon-nucleon interactions like e.g. the proper choice of parameter constraints. In addition, the results obtained with the energy-independent potentials (A, B) in a conventional first-order Brueckner calculation for a LAMBDA-hyperon in nuclear matter are presented. The binding energy B(LAMBDA)(infinity) of a LAMBDA-hyperon in nuclear matter was found to be 29.8 MeV (32.0 MeV) for model A(B).