Double Scattering of High-Energy Protons

Abstract

Measurements of polarization effects in double scattering of protons have been made in the energy range near 200 Mev. With a first scattering angle of 19\ifmmode^\circ\else\textdegree\fi{} and a mean second polar angle of 27\ifmmode^\circ\else\textdegree\fi{}, the azimuthal asymmetry $2\ensuremath{\epsilon}$, the fractional difference between second scattered flux at azimuths 0\ifmmode^\circ\else\textdegree\fi{} and 180\ifmmode^\circ\else\textdegree\fi{}, has been determined with several first and second target materials. With a polyethelene second target, an effective hydrogen target was realized by detecting in coincidence the scattered and recoil protons. By successive use of carbon and polyethelene first targets, with an effective hydrogen second target, the asymmetry in double $p\ensuremath{-}p$ scattering was determined by subtraction to be 9.6\ifmmode\pm\else\textpm\fi{}3.5 percent. Since the fractional polarization, $P$, in a single scatter is related to the asymmetry in a double scatter by $2\ensuremath{\epsilon}=2P{P}^{\ensuremath{'}}$, the polarizations produced in single scatters from hydrogen and carbon were found to be, neglecting energy degradation and angle change, ${P}_{\mathrm{H}}=22\ifmmode\pm\else\textpm\fi{}4$ percent and ${P}_{\mathrm{C}}=43\ifmmode\pm\else\textpm\fi{}8$ percent. A comparison of the double $p\ensuremath{-}p$ asymmetry with those calculated by Goldfarb and Feldman using current $p\ensuremath{-}p$ force models shows that the repulsive core model of Jastrow which best predicts the observed single scattering differential cross sections yields far too little polarization. Considerable singular noncentral force as used in other models seems indicated. The polarized protons produced in scattering from carbon may be useful for other experiments. The polarizations in scattering from several elements in the range from D to Ag, as measured with a hydrogen analyzer, vary from 20 to 50 percent.