EPJ

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EPJ C - Particles and Fields
Particles and Fields

Eur. Phys. J. C 6, 555-574
DOI 10.1007/s100529801031

Determination of ${\rm \vert V_{ub}\vert}$ from the measurement
of the inclusive charmless semileptonic branching ratio
of b hadrons

The ALEPH Collaboration
R.Barate - et al.

Laboratoire de Physique des Particules (LAPP), IN2P3-CNRS, F-74019 Annecy-le-Vieux Cedex, France

Received: 6 May 1998 / Published online: 14 December 1998

Abstract
From a study of the kinematic properties of the final state produced in the semileptonic decays ${\rm b\to X\ell\nu_{\ell}}$, the inclusive charmless semileptonic branching ratio of ${\rm b}$ hadrons is measured. With a sample of 3.6 million hadronic ${\rm Z}$ decays recorded between 1992 and 1995 with the ALEPH detector at LEP, the value ${\rm Br(b\to X_u\ell\nu_{\ell})}$ is determined to be $(1.73\pm 0.55_{{\rm stat}}\pm 0.55_{{\rm syst}})\times 10^{-3}$, where ${\rm X_u}$ represents any charmless hadronic state and ${\rm b}$ is a mixture of b hadrons weighted by their production rates. This measurement yields the result

\begin{displaymath} {\rm \vert V_{ub}\vert^2}= (18.68\pm 5.94_{{\rm stat}}\pm 5.94_{{\rm syst}}\pm 1.45_{HQE})\times 10^{-6},\end{displaymath}

where the last error comes from the conversion of the branching ratio to the CKM matrix element squared.

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