Polarization of Recoil Protons inπ±pElastic Scattering Near 600 MeV

Abstract

Angular distributions of recoil-proton polarization in elastic ${\pi }^{\pm }p$ scattering were measured at 523-, 572-, and 689-MeV incident pion kinetic energy. Polarization measurements were made by observing the azimuthal asymmetry in the subsequent scattering of recoil protons in large carbon-plate spark chambers. Typical strong variation of the polarization with pion scattering angle near the $\pi p$ diffraction minima was observed. Since existing opinion favors a $D_{13}$ resonance at 600 MeV, a phase-shift analysis was attempted in order to confirm the existence and parity of this resonance. Available $\pi p$ total and differential cross sections, these polarization data, and some possible restrictive assumptions related to the 600-MeV resonance were used in the analysis. Though the polarization results aided significantly in restricting the number of acceptable phase-shift sets, still, many plausible and qualitatively different sets were found.