Proton-proton spin correlation measurements at 200 MeV with an internal target in a storage ring

Abstract

Measurements of the $\mathrm{pp}$ spin correlation coefficients ${A}_{\mathrm{xx}},$ ${A}_{\mathrm{yy}},$ and ${A}_{\mathrm{xz}}$ and analyzing power ${A}_{y}$ for $\mathrm{pp}$ elastic scattering at 197.8 MeV over the angular range $4.5\ifmmode^\circ\else\textdegree\fi{}$--$17.5\ifmmode^\circ\else\textdegree\fi{}$ have been carried out. The statistical accuracy is approximately $\ifmmode\pm\else\textpm\fi{}0.01$ for ${A}_{\mathrm{mn}}$ and $\ifmmode\pm\else\textpm\fi{}0.004$ for ${A}_{y},$ while the corresponding scale factor uncertainties are 2.4% and 1.3%, respectively. The experiment makes use of a polarized hydrogen gas target internal to a proton storage ring (IUCF Cooler) and a circulating beam of polarized protons. The target polarization $(Q=0.79)$ is switched in sign and in direction $(x,y,z)$ every 2 s by reversing a weak guide field (about 0.3 mT). The forward-scattered protons are detected in two sets of wire chambers and a scintillator, while recoil protons are detected in coincidence with the forward protons by silicon strip detectors placed 5 cm from the proton beam. The background rate from scattering by the walls of the target cell is $(0.2\ifmmode\pm\else\textpm\fi{}0.2)$% of the good event rate. Analysis methods and comparisons with $\mathrm{pp}$ potential models and $\mathrm{pp}$ partial wave analyses are described.