Soft-core meson-baryon interactions. II. πN and K⁺N scattering

The πN potential includes the t-channel exchanges of the scalar mesons σ and f₀, vector meson ρ, tensor mesons f₂ and f₂^', and the Pomeron as well as the s- and u-channel exchanges of the nucleon N and the resonances Δ, Roper, and S₁₁. These baryonic resonances are not generated dynamically. We consider them, at least partially, as genuine three-quark states, and we treat them in the same way as the nucleon. The Roper and S₁₁ resonances were needed to find the proper behavior of the phase shifts at higher energies in the corresponding partial waves. The soft-core πN model gives an excellent fit to the empirical πN S- and P-wave phase shifts up to T_lab=600 MeV. Also, the scattering lengths have been reproduced well, and the soft-pion theorems for low-energy πN scattering are satisfied. The soft-core model for the K⁺N interaction is an SU_f(3) extension of the soft-core πN model. The K⁺N potential includes the t-channel exchanges of the scalar mesons a₀,σ, and f₀, vector mesons ρ,ω, and ϕ, tensor mesons a₂,f₂, and f₂^', and the Pomeron as well as u-channel exchanges of the hyperons Λ,Σ,Σ(1385), and Λ(1405). The fit to the empirical K⁺N S-, P-, and D-wave phase shifts up to T_lab=600 MeV is reasonable and certainly reflects the present state of the art. Since the various K⁺N phase shift analyses are also not very consistent, scattering observables are also compared with the soft-core K⁺N model. A good agreement for the total and differential cross sections as well as the polarizations is found.