EPJ

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EPJ C - Particles and Fields
Particles and Fields
Eur. Phys. J. C 9, 1-9
DOI 10.1007/s100529900059

A measurement of the product branching ratio $f ({\rm b} \to \Lambda_{\rm b}) \cdot {\rm BR} (\Lambda_{\rm b} \to \Lambda {\rm X})$ in ${\rm Z}^0$ decays

The OPAL Collaboration

G. Abbiendi 2 - et al.

2Dipartimento di Fisica dell' Università di Bologna and INFN, I-40126 Bologna, Italy

Received: 25 November 1998 / Published online: 27 April 1999

Abstract
The product branching ratio, $f ({\rm b} \to \Lambda_{\rm b}) \cdot {\rm BR} (\Lambda_{\rm b} \to \Lambda {\rm X})$,where $\Lambda_{\rm b}$denotes any weakly-decaying b-baryon, has been measured using the OPAL detector at LEP. $\Lambda_{\rm b}$'s are selected by the presence of energetic \ensuremath {\Lambda} particles in bottom events tagged by the presence of displaced secondary vertices. A fit to the momenta of the $\Lambda$ particles separates signal from B meson and fragmentation backgrounds. The measured product branching ratio is

\begin{displaymath} f ({\rm b} \to \Lambda_{\rm b}) \cdot {\rm BR} (\Lambda_{\rm... ...(2.67) \pm 0.38 ({\rm stat})^{+0.67}_{-0.60} ({\rm sys}))\%\; .\end{displaymath}

Combined with a previous OPAL measurement, one obtains

\begin{displaymath} f ({\rm b} \to \Lambda_{\bf b}) \cdot {\rm BR} (\Lambda_{\rm... ...m X}) = (3.50) \pm 0.32 ({\rm stat})\pm 0.35 ({\rm sys}))\%\; .\end{displaymath}

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