Γ(b→ulν)/Γ(b→clν) from the end point of the lepton momentum spectrum in semileptonic<i>B</i>decay

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 \ensuremath{\Gamma}(b\ensuremath{\rightarrow}ul\ensuremath{\nu})/\ensuremath{\Gamma}(b\ensuremath{\rightarrow}cl\ensuremath{\nu}) and a corresponding limit on \ensuremath{\Vert}${V}_{\mathrm{ub}}$\ensuremath{\Vert}/\ensuremath{\Vert}${V}_{\mathrm{cb}}$\ensuremath{\Vert}.