Nuclear shell effects in helion polarization phenomena.

Abstract

The helion elastic scattering cross section and polarization data for a target mass range 16\ensuremath{\le}A\ensuremath{\le}48 are fitted using the optical model, where the spin-orbit potential is deduced microscopically. The quenching effects on the spin-orbit potential of the nucleons occupying the spin-unsaturated shells in the target have been included through the nucleon-nucleus interaction in two different ways, one being an ad hoc approach, while the other is based on more rigorous calculations recently presented in the literature. Both methods produce very similar results and the predictions are comparable to the completely phenomenological approach, despite the contrasting shapes of the microscopic and phenomenological spin-orbit potentials. The valence quenching effects on elastic polarization are found to be small. The deduced N-nucleus spin-orbit potential strengths are consistent with the values obtained using realistic nucleon-nucleon calculations for the targets near closed-shell nuclei. The effects of using different nuclear densities and the sensitivity to the helion wave function are described.