Parity Nonconservation inF18and Meson-Exchange Contributions to the Axial Charge Operator

Abstract

A simple relationship between the one-body and exchange-current contributions to the axial charge operator may allow a separation of these amplitudes in the $\ensuremath{\beta}$-decay transition $^{18}\mathrm{Ne}({J}^{\ensuremath{\pi}}I={0}^{+}1)\ensuremath{\rightarrow}^{18}\mathrm{F}({J}^{\ensuremath{\pi}}I={0}^{\ensuremath{-}}0)$. Since the exchange-current operator is related by isospin rotation to the pion-exchange component of the parity-nonconserving nucleon-nucleon potential, this suggests that the parity-nonconserving pion coupling can be extracted, with minimal dependence on nuclear models, from circular-polarization measurements for the analog $\ensuremath{\gamma}$ decay in $^{18}\mathrm{F}$.