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The European Physical Journal C
ISSN: 1434-6044 (printed version)
ISSN: 1434-6052 (electronic version)
Abstract Volume 2 Issue 2 (1998) pp 197-211
experimental physics:
Measurement of the b baryon lifetime and branching fractions in Z decays
The ALEPH Collaboration
, R. Barate et al.
Laboratoire de Physique des Particules (LAPP), IN2P3-CNRS, F-74019 Annecy-le-Vieux Cedex, France
Received: 15 August 1997 / Online publication: March 10, 1998
Abstract. Using approximately 4 million hadronic Z decays recorded with the aleph detector from 1991 through 1995, the lifetime of the b baryon is measured with three independent methods. From the impact parameter distribution of candidate leptons in 1063 events with $\Lambda\ell^-$ combinations, the average b baryon lifetime is measured to be $1.20\pm{0.08}\pm{0.06}$ ps. From a sample of 193 fully reconstructed $\Lambda^+_{\rm c}$ candidates correlated with a lepton and a sample of 46 $\Lambda\ell^+\ell^-$ combinations, the $\Lambda_{\rm b}$ lifetime is measured to be $1.21\pm{0.11}$ ps. The product branching fractions to these final states are ${\rm Br(b\to \Lambda_{\rm b}}\cdot{\rm BR (\Lambda_{\rm b} \to \Lambda\ell^-\overline\nu X}) = 0.326\pm{0.016}\pm{0.039}$% for the first sample and ${\rm Br(b\to \Lambda_{\rm b}}\cdot{\rm BR(\Lambda_{ \rm b} \to \Lambda^+_{\rm c}\ell^-\overline\nu X}) =0.86\pm{0.07}\pm{0.14}$% for the second and third samples combined.
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Online publication: April 8, 1998
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