Improved Measurement of|Vub|with Inclusive SemileptonicBDecays

We report a new measurement of the Cabibbo-Kobayashi-Maskawa parameter $|V_{\mathrm{ub}}|$ made with a sample of $9.7\times {10}^6$ $B\overline{B}$ events collected with the CLEO II detector. Using heavy quark theory, we combine the observed yield of leptons from semileptonic $B$ decay in the end-point momentum interval $2.2–2.6\mathrm{GeV}/c$ with recent CLEO II data on $B\to X_s\gamma$ to find $|V_{\mathrm{ub}}|=(4.08\pm 0.34\pm 0.44\pm 0.16\pm 0.24)\times {10}^{-3\mathrm{}}$, where the first two uncertainties are experimental and the last two are from theory.