POLARIZATION MEASUREMENTS ON THE RECOIL PROTON FROM PION (O) PHOTOPRODUCTION,

The polarization of the recoil proton in piono photoproduction off hydrogen has been measured for photons in the range 500-1000 MeV, using the Stanford Mark III linear accelerator. Protons were detected at an angle b and momentum analyzed using a 90 degree magnetic spectrometer. The scattered protons were detected by two counter telescopes placed symmetrically to left and right of the carbon target and making angles C with respect to the direction of a proton emerging from the spectrometer. The measured asymmetry was obtained from the usual formula e L-RLR and the proton polarization Pb was then obtained by substituting the known carbon analyzing power Ac in the equation eb,c Pb Ac. Using parity conservation it can be shown that Pb -Pb. Thus the running time was equally divided between measurements with the spectrometer at b and -b. This technique enabled residual artificial asymmetries to be removed, since these do not change sign when b becomes -b. Preliminary results are presented and compared to existing data from various laboratories. Author