B semileptonic decays at the Upsilon (4S) and the Upsilon (5S).

{ital B}-meson semileptonic decay spectra have been obtained at the {Upsilon}(4{ital S}) and at the {Upsilon}(5{ital S}) at the Cornell Electron Storage Ring with the Columbia University--Stony Brook detector. The branching ratio for {ital B}{r arrow}{ital e}{nu}{ital X} at the {Upsilon}(4{ital S}) is found to be (10.0{plus minus}0.5)%. The electron spectrum of {ital B}{r arrow}{ital e}{nu}{ital X} at the {Upsilon}(5{ital S}) is observed for the first time and the average branching ratio of {ital B},{ital B}{sub {ital s}}{r arrow}{ital e}{nu}{ital X} is consistent with that for {ital B}'s from {Upsilon}(4{ital S}) decays. The shape of the electron spectrum at the {Upsilon}(5{ital S}) indicates production of {ital B} mesons which are heavier than nonstrange {ital B}'s, presumably strange {ital B}'s.