Development of a Parity Violation Experiment for Undergraduate Laboratories
An undergraduate experiment is being developed at Houghton College to measure weak nuclear parity violation. Parity violation, discovered in 1956-57 by Lee and Yang , and Wu , was a breakthrough in modern physics, but has yet to make its way into undergraduate laboratories. Following a method originally suggested by Lee and Yang, a coincident counting experiment is being developed to measure the transmission through magnetized iron of circularly polarized gamma rays from 60Co beta decay. A BGO gamma detector and silicon beta detector, collinear on either side of a 60Co source with a steel electromagnet core between the source and gamma detector, measure the gamma rays in coincidence with the beta particles. Since the Compton scattering cross section in the magnetized steel depends on the relative orientations of the gamma ray spin and the spin of the polarized electrons in the magnet, an asymmetry in the transmission count rate when the magnet is polarized in opposite directions demonstrates that parity is violated.