Polarization of Recoil Protons from Neutral Pion Photoproduction

Abstract

The polarization of the recoil proton in the process γ+ P → p +π° was measured for a pion angle of 120° in the center of mass system at photon energies 450, 500, 550 and 600 Mev. Magnetically-analyzed protons were detected by a counter telescope consisting of three scintillation counters, which triggered the spark chamber system designed as a polarization analyzer. About 150 thousand spark chamber photographs were taken, and the tracks of protons quasi-elastically scattered by the carbon plates of the spark chamber and by a carbon block in its front were selected by manual scanning. Data from about 5000 photographs thus selected were processed by an electronic computer. Results obtained are: -0.07±0.18 for 450 MeV, -0.25±0.14 for 500 MeV, -0.38±0.12 for 550 Mev and -0.43±0.18 for 600 meV.