Parity violation in polarized p-p scattering at 222 MEV

An experiment is in progess at TRIUMF to measure the parity-violating longitudinal analyzing power Az in polarizedp-p scattering at 222 MeV. Previous measurements at 15 and 45 MeV have determined the parity-mixed partial wave scattering amplitude to high precision. In contrast, only the (3P2-1D2) amplitude contributes to Az at 222 MeV. These two amplitudes yield complementary information on the underlying parity violating reaction mechanism. In a weak meson exchange model, the (3P2-1D2) amplitude is entirely due to rho meson exchange, and the present experiment affords a unique opportunity to measure the weak ρ-N coupling strength hρ. At TRIUMF, a 500 nA beam of longitudinally polarized protons (pz∼0.8) from the optically pumped polarized ion source will be scattered from a 20 cm liquid hydrogen target. A unique feature of this experiment is that Az will be measured in two different geometries (scattering and transmission mode) simultaneously, which will provide a crucial consistency check on the results. Monte Carlo simulations have confirmed that d.c. ionization chambers used to collect the transmitted and scattered protons in the two simultaneous measurements will achieve comparable statistical accuracies in the ∼ 300 hour counting time proposed for the experiment. High precision monitoring devices are being constructed and tested at TRIUMF to monitor changes in beam properties, such as beam position and residual transverse polarization, that can contribute to systematic errors in the parity violation measurements. The present status of the detector developments and systematic error controls will be discussed