Measurement of the Electron Asymmetry in the Beta Decay of PolarizedΣ−Hyperons

We report the results of a Fermilab Tevatron experiment using a ${\Sigma }^{-}$ beam with a measured polarization of 0.22 ± 0.04. We find the electron asymmetry in ${\Sigma }^{-}$ beta decay to be ${\alpha }_e=-0.53\mathrm{}\pm 0.14$ on the basis of a sample of 25 000 events, in agreement with the Cabibbo model and in contradiction with previous experiments. The corresponding value for the ratio of axial-vector to vector form factors is $\frac{g_1}{f_1}=-0.29\mathrm{}\pm 0.07$.