Measurements of the Branching Ratio and form of Interaction for the Beta Decay of theΛHhyperon

In a stopping-$K^{-}$ exposure of the Brookhaven National Laboratory 30-in. hydrogen bubble chamber, we have found 204 $\Lambda$ $\beta$ decays, $\Lambda \to p+e^{-}+{\overline{\nu }}_e$, with a scanning efficiency of 0.97±0.02. We obtain a branching ratio of (0.80±0.08)×${10}^{-3\mathrm{}}$. Using SU(3) and conservation of vector current to determine the weak-magnetism to vector form-factor ratio in the baryon current, we find an axial-vector-to-vector ratio of ${0.72}_{-0.14\mathrm{}}^{+0.19\mathrm{}}$. The results are in good agreement with Cabibbo theory and are insensitive to the relative strength of weak magnetism.