Relativistic spin effects and three-body forces in P-D scattering

Abstract

We analyze the structure of the (3→3)-nucleon amplitude appearing in proton-deuteron elastic scattering amplitude. We calculate that part of the amplitude, which can be unambiguously expressed, through analyticity and unitarity, in terms of physical (2→2)-nucleon amplitudes. By comparing the result with the experimental data on spin observables we find that it is necessary to add extra terms, which must be interpreted as 3-body effects. These 3-body forces, of the type of contact interactions, are also required by the high-energy asymptotics of the amplitudes involved, and can be, to some extent, determined from soft-pion theorems. Much more information on them should become available through systematic analysis of the spin structure of p-d scattering amplitudes.