Determination of vertical bar V-ub vertical bar from the measurement of the inclusive charmless semileptonic branching ratio of b hadrons

From a study of the kinematic properties of the final state produced in the semileptonic decays b --> Xlv(e), the inclusive charmless semileptonic branching ratio of b hadrons is measured. With a sample of 3.6 million hadronic Z decays recorded between 1992 and 1995 with the ALEPH detector at LEP, the value Br(b --> X(u)lv(e)) is determined to be (1.73 +/- 0.55(stat) +/- 0.55(syst)) x 10(-3), where X-u represents any charmless hadronic state and b is a mixture of b hadrons weighted by; their production rates. This measurement yields the result /V-ub/(2) = (18.68 +/- 5.94(stat) +/- 5.94(syst) +/- 1.45(HQE)) x 10(-6) where the last error comes from the conversion of the branching ratio to the CKM matrix element squared.