Complementary observables for the determination of |Vub| in inclusive semileptonic B decays

The determination of |V{sub ub}| from inclusive semileptonic B decays is limited by uncertainties in modeling the decay distributions in b {yields} u{ell}{nu} transitions. The largest uncertainties arise from the limited knowledge of the appropriate b quark mass and Fermi momentum to use in the parameterization of the shape function. This paper presents a new method in which these shape function parameters are constrained by the same data used to measure |V{sub ub}|. The method requires measurements of the momenta of both the charged lepton and the neutrino in semileptonic B decays. From these quantities two complementary observables can be constructed, one for discriminating between b {yields} u{ell}{nu} transitions and background and the other for constraining the shape function. Using this technique the uncertainties in |V{sub ub}| from the shape function may be significantly reduced.