Damped Pseudoscalar- and Vector-Meson Model for Nucleon-Nucleon Scattering

Recently, a pseudoscalar-vector-meson (PV) model for elastic nucleon-nucleon scattering was presented by Barker and Haracz in which phase parameters are defined by a perturbative method which is similar to the geometric unitarization scheme used in other models. These phase parameters are dominated by the two-pion-exchange (TPE) contribution for the low values of L, and TPE is unreasonably large for the phases associated with the S state. In order to suppress this large contribution, relativistic Heitler damping or K-matrix unitarization is applied to the PV model. It is found that the low-partial-wave phase parameters ¹K₀, ³θ^S₁, ³θ^D₁, and ρ₁ are drastically reduced and made much more reasonable by damping. Moreover, the P-and D-state phase shifts are reduced by as much as 20% at the higher scattering energies. The resulting damped phase parameters are in good agreement with the phenomenological values for L>=2 and energies up to 200 MeV, excluding ³θ^D₁. Coupling constants more consistent with experiment are used contrasting with our previous usage. It is also found that the presence of a strongly coupled scalar ɛ resonance does not improve this model.