Extension of the Bonn meson exchange NN potential above pion production threshold: Nucleon renormalization and unitarity

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Abstract
Nucleon self-energy diagrams, which are necessary to satisfy unitarity in NN scattering above pion production threshold, are studied for a realistic one-boson-exchange model. It is demonstrated that, in the framework of noncovariant perturbation theory, the independent iteration of (lowest order) bubble diagrams at both nucleon lines leads to dressing factors which provide well-defined off-shell corrections to the meson exchange contributions. It turns out that nucleon dressing yields additional attraction in lower partial waves. A slight readjustment of meson parameters (especially a reduction of the cutoff mass in the πNN vertex) leads to a reproduction of the empirical NN data below pion threshold which is of the same quality as before. The resulting inelasticities are, however, much too small, which clearly establishes the need for using a NN potential model containing the Δ isobar explicitly.