Proton-helium elastic scattering: a possible high-energy polarimeter at RHIC-BNL

We examine a suggestion to use p-4He elastic scattering, as an absolute polarimeter for high-energy polarized proton beams, by means of a Coulomb-Nuclear Interference effect for the single-spin asymmetry AN(t), around the diffractive minimum of the differential cross section |t|∼0.21 GeV2. Although this reaction has a fairly simple dynamical structure, our theoretical uncertainties and the present experimental inaccuracy of the differential cross section in this t region, allows one to generate dramatic effects for AN(t), which will be discussed.