Covariant separable interaction for the neutron–proton system in image–image partial-wave state

Within a covariant Bethe–Salpeter approach a rank-six separable neutron–proton interaction kernel for the triplet coupled image partial-wave state is constructed. Two different methods of a relativistic generalization of initially nonrelativistic form factors parametrizing the kernel are considered. The model parameters are determined by fitting the elastic image and image phase shifts and the triplet scattering length as well as the asymptotic image ratio of the deuteron wave functions and the deuteron binding energy. The D-state probability constraints 4–7% are taken into account. The deuteron magnetic moment is calculated. The half-off-shell properties are further demonstrated by the Noyes–Kowalski functions. The first test of the constructed kernel is performed by calculating the deuteron electrodisintegration at three different kinematic conditions.