The 2+ 1 to 3+ 1 transition in 22na and the second class current problem

Abstract

This thesis is motivated by searches of second-class currents with semi-leptonic β decays. The standard model predicts very small effects from second-class currents on account of the relatively small mass difference between the up and down quarks. Despite this prediction, detailed studies of specific nuclear β decays have suggested unusually large second-class currents that are contrary to expectations. The measured β − γ angular correlation from 22Na β decay presents one such example, where an unexpectedly large second-class form factor is required to describe the data. To further investigate the discrepancy, this work aims to determine the magnetic dipole (M1) strength of the 2+ 1 → 3 + 1 transition in 22Na, which is the analogue electromagnetic transition to the β decay. A 21Ne(p, γ) resonance reaction was used to produce the analogue 2 + 1 level. Angular distribution measurements were performed with high-purity Germanium detectors to determine the E2/M1 mixing ratio for the transition. Together with the conserved vector current hypothesis, these data were used to determine the weak magnetism form factor for 22Na β decay, as a means to resolve the anomaly