Direction of Proton Spin Polarization Produced by Elastic Scattering

A measurement has been made of the direction of spin polarization produced by elastic scattering of high-energy protons. 435-Mev protons were polarized by scattering elastically from beryllium to the right at 14° after which they were slowed to 0-20 Mev and scattered again elastically from helium. From the measured energies and angles of the scattered protons as recorded in photographic emulsions, together with the calculated polarizations resulting from interferences among the levels of the doublet $P$ state involved in proton-helium elastic scattering, we find that the polarization of the proton beam is directed down. This result has been predicted by an hypothesis which extrapolates to high energies the effect of the spin-orbit coupling postulated for the nuclear shell model.