Tensor and Spin-Orbit Forces in Nucleon-Nucleon Scattering

In order to investigate effects of a tensor force and to examine necessity of introducing a spin-orbit force at high energies, nucleon-nucleon scattering at 150 Mev is analysed. The analysis is made taking into account some characteristic features of the pion-theoretical nuclear forces. It is shown that the experimental data around 150 Mev can be well explained by two main features of nuclear forces; (i) a strong tensor force in the outer part of the interaction and (ii) a hard-core-like repulsive interaction in the inner part. It should be emphasized that the former feature, which is the most characteristic one of the pion-theoretical nuclear forces, is decisively important at such high energies as well as at low energies. We find no positive evidences for such spin-orbit forces as play an important role around 150 Mev. This conclusion is in conflict with the prediction of very strong spin-orbit forces recently made by Signell and Marshak and by Gammel and Thaler. This point is discussed quite in detail. Especially, it is shown that Signell and Marshak's spin-orbit coupling potential comes from their undue reliance on the inner part of Gartenhaus' potential.