Two-Nucleon Interactions, the Unitary Model, and Polarization in Elastic Nucleon-Deuteron Scattering

The use of the first-order unitary model to calculate nucleon polarizations in elastic nucleon-deuteron scattering at energies up to 40 MeV is investigated. One shortcoming of extant unitary-model calculations, that of inadequate two-nucleon input, is partially remedied by introducing a variety of more realistic models for the two-nucleon interaction. It is found that even with the latter interactions the unitary model fails to represent the nucleon polarization, and, as is to be expected from the work of Sloan et al., to a lesser degree, the elastic differential cross section. The nucleon polarization is found to be extremely sensitive even at fairly low energies to the presence of the $P$-wave components of the two-nucleon amplitudes when the three-particle scattering is computed via the unitary and other approximations. This indicates that any method (exact or otherwise) for computing polarizations in $N-d$ scattering must include these components.