Abstract Using the CLEO II detector at CESR we observe 500 Λ l + pairs consistent with the semileptonic decay Λc+ → λ+ν We measure σ(e + e − → Λ + c X) · B(Λ + c → Λ l + ν l ) = 4.77±0.25±0.66 pb . Combining with the charm semileptonic width and the lifetime of the Λc we also obtain B(Λ+c → pK−π+). We find no evidence for Λ l + ν l final states in which there are additional Λ+c decay products. We measure the decay asymmetry parameter of Λ+c → Λe+νe to be αΛc = −0.89+0.17+0.09−0.11−0.05.
