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

The electron asymmetry was measured in the beta decay of polarized sigma hyperons ${\Sigma }^{-}\to n{e}^{-}\overline{\nu }$ produced in the reaction $K^{-}p\to {\Sigma }^{-}{\pi }^{+}$ at the ${Y_0}^{*}\mathrm{}\left(1520\right)\mathrm{}$ resonance. Particles were tracked in a magnetic spectrometer and a large-acceptance, segmented, gas-Cherenkov-scintillation counter array identified electrons. A maximum-likelihood analysis based on 193 events yields the electron asymmetry of ${\alpha }_e=0.35\mathrm{}\pm 0.29$. The result favors a positive value for $\frac{g_1}{f_1}$ which is opposite to the Cabibbo-favored sign.