Precision determination of vertical bar Vub vertical bar from inclusive decays - art. no. 113004

We propose determining \V-ub\ from inclusive semileptonic B decay Using com bined cuts on the leptonic and hadronic invariant masses to eliminate the b -c background. Compared to a pure dilepton invariant mass cut, the uncertai nty from unknown order A(QCD)(3)/m(b)(3) terms in the operator product expa nsion is significantly reduced and the fraction of b-u events is roughly do ubled. Compared to a pure hadronic invariant mass cut, the uncertainty from the unknown light-cone distribution function of the b quark is significant ly reduced. We find that \V-ub\ can be determined with theoretical uncertai nty at the 5-10% level.