Study of the Decay $\Lambda_c \to \Lambda l^+ \nu_{l}

Abstract

Using the CLEO II detector at CESR, we observe 500 $\Lambda l^{+}$ pairs consistent with the semileptonic decay ${\Lambda }_c\to \Lambda l^{+}{\nu }_l$. We measure $\sigma (e^{+}{e}^{-}\to {\Lambda }_{c}X)\dot{calB}({\Lambda }_c^{+}\to \Lambda l{\nu }_l)=4.77\pm 0.25\pm 0.66$pb. Combining with the charm semileptonic width and the lifetime of the ${\Lambda }_c$, we also obtain $\mathcal{B}({\Lambda }_c\to p{K}^{-}{\pi }^{+})$. We find no evidence for $\Lambda l^{+}{\nu }_l$ final states in which there are additional ${\Lambda }_c^{+}$ decay products. We measure the decay asymmetry parameter of ${\Lambda }_c\to \Lambda l^{+}{\nu }_l$ to be $\alpha_{\Lambda_c} =-0.89\pm{^{0.17}_{0.11}}\pm{^{0.09}_{0.06}}.

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