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∣∼0.21GeV2. 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.Comment: 8 pages, Latex, 4 figure