Measurement of the inclusive charmless semileptonic branching fraction of beauty hadrons and a determination of |Vub| at LEP

A measurement of the inclusive charmless semileptonic branching fraction of beauty hadrons, b→Xuℓν, has been performed using almost two million hadronic Z decays collected by the L3 experiment at LEP, yielding the result: Br(b→Xuℓν)=(3.3±1.0±1.7)×10−3. The first uncertainty is statistical and the second is systematic. The modulus of the Cabibbo-Kobayashi-Maskawa matrix element Vub extracted from this measurement is: |Vub|=(6.0+0.8−1.0+1.4−1.9±0.2)×10−3, where the uncertainties are statistical, systematic and theoretical, respectively.