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Abstract

The magnitude of the CKM matrix element |V[sub ub]| is determined by measuring the inclusive charmless semileptonic branching fraction of beauty hadrons at OPAL based on b  X[sub u]lv event topology and kinematics. This analysis uses OPAL data collected between 1991 and 1995, which correspond to about four million hadronic Z decays. Bv(b X[sub u]lv) is measured to be (1.63 ± 0.53 [sup+0.55][sub -0.62]) x 10 ⁻³. The first uncertainty is the statistical error and the second is the systematic error. From this analysis, |V[sub ub]| is determined to be: |V[sub ub]| = (4.00 ± 0.65 (stat) [sup +0.67][sub -0.76] (sys) ± 0.19 (HQE)) x 10 ⁻³. The last error represents the theoretical uncertainties related to the extraction of |V[sub ub]| from Br(6 —> X[sub u]lv) using the Heavy Quark Expansion.