Γ(b→ulν)/Γ(b→clν) from the end point of the lepton momentum spectrum in semileptonicBdecay

We have used the measured yield of leptons near the end point of the momentum spectrum from semileptonic B decay to obtain an upper limit on {Γ}(b{→}ul{ν})/{Γ}(b{→}cl{ν}) and a corresponding limit on {}Vub{}/{}Vcb{}.