Observation of 1.5% Parity-Nonconservingγ-Ray Asymmetry

Abstract

The angular distribution of the 501-keV $\gamma$ radiation from low-temperature polarized ${}_{}{}^{180m}{}_{}{}^{}\mathrm{Hf}$ was found to exhibit a very large parity-nonconserving forward-backward asymmetry. At a polarization of 71%, the measured asymmetry is -(1.49 ± 0.25)%. This asymmetry corresponds to an $\frac{\tilde{E}2}{M2\mathrm{}}$ mixing ratio of magnitude 0.038 ± 0.007 in fairly good agreement with circular-polarization experiments. We also deduce the $\frac{E3\mathrm{}}{M2\mathrm{}}$ mixing ratio to be +6.0 ± 0.5, agreeing with angular-correlation measurements.