Extracting |Vub| from the hadronic mass spectrum of inclusive B decays

Following a strategy introduced earlier by the authors, we show that it is possible to extract |Vub| from the cut hadronic mass spectrum of B decays without large systematic errors which usually arise from having to model the Fermi motion of the heavy quark. We present a closed form expression for |Vub|/|Vts| which is accurate up to corrections of order αs2, αsρ, (Λ/mb)2/ρ, where ρ is the experimental cut (sc/mb2) on the hadronic mass used to veto charmed decays. Modulo duality violation errors, which are intrinsic to all inclusive predictions, we estimate the theoretical error in the extraction to be at the 5% level.