Study of the Decay $Λ_c \to Λl^+ ν_{l}

Abstract

Using the CLEO II detector at CESR, we observe 500 $Λl^+$ pairs consistent with the semileptonic decay $Λ_c \to Λl^+ ν_{l}$. We measure $σ(e^+ e^- \to Λ_c X) \dot {cal B}(Λ_c^+ \to Λl ν_{l}) =4.77 \pm 0.25 \pm 0.66 $pb. Combining with the charm semileptonic width and the lifetime of the $Λ_c$, we also obtain ${\cal B}(Λ_c \to p K^- π^+)$. We find no evidence for $Λl^+ ν_{l}$ final states in which there are additional $Λ_c^+$ decay products. We measure the decay asymmetry parameter of $Λ_c \to Λl^+ ν_{l}$ to be $α_{Λ_c} =-0.89\pm{^{0.17}_{0.11}}\pm{^{0.09}_{0.06}}.