Constraints On Weak Meson-Nucleon Coupling From Parity Nonconservation In F-19

The parity-nonconservation asymmetry ${A}_{\ensuremath{\gamma}}$ in the decay of polarized $^{19}\mathrm{F}^{*}$ (110-keV) nuclei has been measured to high precision and is found to be ${A}_{\ensuremath{\gamma}}=\ensuremath{-}(6.8\ifmmode\pm\else\textpm\fi{}1.8)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$. Absolute uncertainties have been largely removed. This new value for ${A}_{\ensuremath{\gamma}}$ together with recent nuclear structure calculations provides severe constraints on the weak meson-nucleon coupling constants, in particular on ${f}_{\ensuremath{\pi}}$ and ${h}_{\ensuremath{\rho}}^{0}$.