Determination of|Vub|from Measurements of the Electron and Neutrino Momenta in Inclusive SemileptonicBDecays

We present a determination of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{ub}|$ based on the analysis of semileptonic $B$ decays from a sample of $88\times {10}^6$ ${\rm Y}(4S)$ decays collected with the BABAR detector at the SLAC PEP-II $e^{+}{e}^{-}$ storage ring. Charmless semileptonic $B$ decays are selected using measurements of the electron energy and the invariant mass squared of the electron-neutrino pair. We obtain $|V_{ub}|=(3.95\pm {0.26}_{-0.42}^{+0.58}\pm 0.25)\times {10}^{-3}$, where the errors represent experimental uncertainties, heavy quark parameter uncertainties, and theoretical uncertainties, respectively.