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

Abstract

A measurement of the inclusive charmless semileptonic branching fraction of beauty hadrons, b→X_uℓν, has been performed using almost two million hadronic Z decays collected by the L3 experiment at LEP, yielding the result: Br(b→X_uℓν)=(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 V_ub extracted from this measurement is: <math><mtext>|</mtext><mtext>V</mtext><msub><mi></mi><mn>ub</mn></msub><mtext>|=(6.0</mtext><mspace sp="0.2" width="2px" linebreak="nobreak" is="true"></mspace><msup><mi></mi><mn>+0.8</mn></msup><msub><mi></mi><mn>−1.0</mn></msub><mspace sp="0.2" width="2px" linebreak="nobreak" is="true"></mspace><msup><mi></mi><mn>+1.4</mn></msup><msub><mi></mi><mn>−1.9</mn></msub><mtext>±0.2)×10</mtext><msup><mi></mi><mn>−3</mn></msup><mtext>,</mtext></math> where the uncertainties are statistical, systematic and theoretical, respectively.