Experimental Investigation ofV−Ain Leptonic Lambda Decay

Abstract

Twenty-two $\Lambda \to p^{+}+e^{-}+\overline{\nu }$ events were observed from $K^0{\Lambda }^0$ production in hydrogen, for which the lambdas are highly polarized and three events from $K^0{\Sigma }^0$ production. The 22 polarized events were studied as to the space-time properties of the interaction currents. Assuming vector and axial vector currents, a likelihood fit to the data was used to determine a best value for the ratio and sign of the coupling strengths $k=\frac{C_A}{C_V}$. The data was most consistent with $C_V=-C_A$. Higher order terms in the coupling form factors were looked at, but the statistical errors were too large to permit any significant statements concerning them. The branching ratios for ${\Lambda }_e$ and ${\Lambda }_{\mu }$ decays are reported and are consistent with $V-A$ and muon-electron universality. Finally, the values obtained for $k$ and the ${\Lambda }_e$ branching ratio are compared to the theory of $N$. Cabibbo and seen to be in remarkable agreement.