Parity violation in p-p scattering: the TRIUMF experiment

Parity violation in proton-proton elastic scattering provides a unique window on the hadronic weak interaction. At low and intermediate energies, the coupling constants of an effective meson exchange model provide an appropriate parametrization. Measurements at different beam energies permit the lowest partial wave amplitudes to be determined in a model independent framework. The TRIUMF cyclotron provides a unique opportunity to measure the 3P2−1D2 contribution to proton-proton parity violation at 221 MeV beam energy. This partial wave in turn isolates the weak ρ meson exchange contribution, which is only known to within a factor of 2 from theoretical estimates. An experiment underway for many years at TRIUMF completed data taking in 1999, and the analysis is now nearing completion. Preliminary results, based on half of the acquired data sample, are consistent with the meson exchange model prediction at this beam energy.