Measuring Parity Violation in Cobalt-60 Decay

Abstract

An experiment was performed to measure parity violation in the decay of 60Co. Measurements of the correlation between the circular polarization of ?-rays and ?-particles were made by measuring the circular polarization of the decay ?-ray emitted at 180° from the correlated ?-particle. A ?-? coincidence circuit counted gamma rays transmitted through a magnetized iron core. Since the Compton scattering cross-section for circularly polarized ?-rays depends on the spin orientation of the electrons in the magnet, an asymmetry in the count rate when the electron and photon spins are parallel and anti-parallel indicates parity violation. While only initial measurements have been made to date, in the future it should be possible to measure the asymmetry to within approximately 5%.