Abstract
Firstly a soft-core model for the pion-nucleon interaction in momentum space is derived. Gaussian form factors are included and strong dynamical pair suppression is assumed. The pion-nucleon potential includes the t-channel exchanges of scalar-, vector-, tensor-mesons and the Pomeron as well as s- and u-channel exchanges of the nucleon and the resonances Delta, Roper and S11. These resonances are not generated dynamically. We consider them as, at least partially, genuine three-quark states and treat them in the same way as the nucleon. The latter two resonances were needed to find the proper behavior of the phase shifts at higher energies in the corresponding partial waves. The model gives an excellent fit to the empirical S- and P-wave phase shifts up to pion laboratory energy 600 MeV. Also the scattering lengths have been reproduced well and the soft-pion theorems for pion-nucleon scattering are satisfied. This soft-core pion-nucleon model provides a good basis for a kaon-nucleon model. Secondly a soft-core model for the positive strangeness kaon-nucleon interaction is derived. This model is an SU(3)-extension of the soft-core pion-nucleon model, similar to the successful Nijmegen nucleon-nucleon and hyperon-nucleon models. The kaon-nucleon potential includes the t-channel exchanges of scalar-, vector-, tensor-mesons and the Pomeron as well as u-channel exchanges of the hyperons Lambda and Sigma. The fit to the empirical S-, P- and D-wave phase shifts up to kaon laboratory energy 600 MeV is reasonable and reflects the present state of the art. Since the various kaon-nucleon phase shift analyses are not very consistent, also scattering observables are compared directly with the kaon-nucleon model. A good agreement for the total and differential cross sections and the polarizations is found.
