On the DecaysΣ±→Λ0+e±+ν

We have scanned 550 000 pictures of stopping ${K}^{\ensuremath{-}}$ mesons in hydrogen for the decays ${\ensuremath{\Sigma}}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}\ensuremath{\Lambda}+{e}^{\ifmmode\pm\else\textpm\fi{}}+\ensuremath{\nu}$, and find ${\ensuremath{\Sigma}}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\Lambda}+{e}^{\ensuremath{-}}+\ensuremath{\nu}/\mathrm{all}$ ${\ensuremath{\Sigma}}^{\ensuremath{-}}$ decays to be (0.64\ifmmode\pm\else\textpm\fi{}0.12)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$ and ${\ensuremath{\Sigma}}^{+}\ensuremath{\rightarrow}\ensuremath{\Lambda}+{e}^{+}\ensuremath{\nu}/\mathrm{all}$ ${\ensuremath{\Sigma}}^{+}$ decays to be (0.20\ifmmode\pm\else\textpm\fi{}0.08)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$. The rate for ${\ensuremath{\Sigma}}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\Lambda}+{e}^{\ensuremath{-}}+\ensuremath{\nu}$ yields a value of $D=0.76\ifmmode\pm\else\textpm\fi{}0.07$, and $\ensuremath{\alpha}=\frac{D}{(D+F)}=0.64\ifmmode\pm\else\textpm\fi{}0.06$. The observed electron-neutrino angular correlation together with the lambda polarization determines the magnitude of the ratio of vector to axial-vector coupling for this decay to be 0.31\ifmmode\pm\else\textpm\fi{}0.30, consistent with the hypothesis of conserved vector current, with the absence of second-class currents, and with time-reversal invariance.