NN tensor and LS potentials in a quark model with quark-antiquark excitations

Abstract

A more detailed study is made of the NN interaction in a quark model in which the (qq) excitations inherent in the quark-gluon interaction are explicitly incorporated into the model space. A unified treatment for all types of exchange terms of the (3q)-(3q) to (3q)-(3q)(qq) coupling kernels is used to calculate the space parts of the full coupling kernels and their Wigner transforms in complete analytic form. The present investigation focuses on the noncentral parts of the NN interaction. The tensor force gains almost its full strength from coupling kernels of N[pi] and N[rho] type. If the N[pi] contribution is adjusted to fit the experimental pion-nucleon coupling constant the predicted strength of the full tensor force is in reasonable agreement with that of conventional OBEP's over the range in which the tensor force can act. The LS force gains contributions from both the pure (3q)-(3q) and the coupling kernels, but the dominant contributions (about 60-65% of the triplet-odd LS potential in the 0.7-1.0 fm range), come from the coupling kernels and particularly from the N[omega] and N[rho] components. The triplet-odd LS potential derived from the full quark-exchange kernel is in remarkably good agreement with the OBEP LS potential over the significant range. Both the tensor and LS potentials are approximated surprisingly well over their full range by the simple (qq) exchange terms of our model. The 3P RGM phase shifts are calculated to show that both tensor and LS forces of our quark model are in good agreement with the experimental facts.