Upper Limit on Parity Mixing inNe21

Abstract

The parity-nonconserving circular polarization of $\gamma$ rays from the 2.789 → 0.0 MeV transition in ${}_{}{}^{21}{}_{}{}^{}\mathrm{Ne}$ is found to be (-9 ± 51) × ${10}^{-4\mathrm{}}$, which corresponds to a parity-mixing matrix element $\left|〈H_{\mathrm{PNC}}〉\right|=0.009\mathrm{}\pm 0.054$ eV between the 2.80-MeV, $J^{\pi }={\frac{1}{2}}^{\pm }$ levels. This value is considerably smaller than the measured parity mixing in the $J=\frac{1}{2}$ doublet in ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$.