We report on new measurements of the ${\Sigma }^{+}$ and ${\Sigma }^{-}$ lifetimes, the ${\Sigma }^{+}$ nonleptonic-decay branching ratio, and the ratio of the ${\Sigma }^{+}$ decay asymmetry parameters $\frac{{\alpha }_{+}}{{\alpha }_0}$. The final results obtained are ${\tau }^{+}=(0.798\mathrm{}\pm 0.005)\times {10}^{-10\mathrm{}}$ sec, ${\tau }^{-}=(1.480\mathrm{}\pm 0.014)\times {10}^{-10\mathrm{}}$ sec, $R=\frac{\Gamma ({\Sigma }^{+}\to p{\pi }^0)}{\Gamma ({\Sigma }^{+}\to \mathrm{all})}=0.5172\mathrm{}\pm 0.0036$, and $\frac{{\alpha }_{+}}{{\alpha }_0}=-0.073\mathrm{}\pm 0.021$. These results together with the world average for ${\alpha }_0$ are used to perform a test of the $\left|\Delta I\right|=\frac{1}{2}$ rule.

• Received 26 December 1979

DOI:https://doi.org/10.1103/PhysRevD.21.2501