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Particles and Fields

Eur. Phys. J. C 21, 399-410 (2001)
DOI: 10.1007/s100520100764

Measurement of $\vert\rm {V}_{\rm {ub}}\vert$ using b hadron semileptonic decay

The OPAL Collaboration G. Abbiendi and et al.

Dipartimento di Fisica dell' Università di Bologna and INFN, 40126 Bologna, Italy

(Received: 26 June 2001 / Published online: 31 August 2001 -© Springer-Verlag / Società Italiana di Fisica 2001 )

The magnitude of the CKM matrix element \(\vert\rm {V}_{\rm {ub}}\vert\) is determined by measuring the inclusive charmless semileptonic branching fraction of beauty hadrons at OPAL based on \(b \to \rm {X}_{\rm {u}} \ell \nu \) event topology and kinematics. This analysis uses OPAL data collected between 1991 and 1995, which correspond to about four million hadronic Z decays. We measure Br( \(b \to \rm {X}_{\rm {u}} \ell \nu \)) to be (1.63 $\pm$ 0.53 +0.55-0.62) $\times$ 10-3. The first uncertainty is the statistical error and the second is the systematic error. From this analysis, \(\vert\rm {V}_{\rm {ub}}\vert\) is determined to be:

\begin{displaymath}\vert\rm {V}_{\rm {ub}}\vert = (4.00 \pm 0.65 (\rm {stat})
...7}_{-0.76} (\rm {sys}) \pm 0.19 (\rm {HQE})) \times

The last error represents the theoretical uncertainties related to the extraction of \(\vert\rm {V}_{\rm {ub}}\vert\) from Br( \(b \to \rm {X}_{\rm {u}} \ell \nu \)) using the Heavy Quark Expansion.

© Società Italiana di Fisica, Springer-Verlag 2001