Nucleon-nucleon potentials with and withoutΔ(1232)degrees of freedom

Abstract

We present two new nucleon-nucleon (NN) potentials: a $v_{14}$ model that is a conventional NN potential and a $v_{28}$ model with explicit $\Delta \mathrm{}\left(1232\right)\mathrm{}$ degrees of freedom. The $v_{14}$ model has 14 operator components describing NN channels, while the $v_{28}$ model has 14 additional operators, including 12 transition operators for all possible $\pi \mathrm{N}\Delta$ and $\pi \Delta \Delta$ couplings and two central operators for $\mathrm{N}\Delta$ and $\Delta \Delta$ channels; the latter are constrained so that the $v_{28}$ model has no additional free parameters for data fitting. The two models give excellent and almost identical fits to deuteron properties and np scattering below 330 MeV. The $v_{14}$ and $v_{28}$ forms are convenient for nuclear structure calculations; when many-body cluster contributions are evaluated the $v_{28}$ model will automatically include much of the effect attributed to many-body forces in conventional models, while the $v_{14}$ model will provide a standard of comparison.