EPJ

2023 Impact factor 4.2
EPJ C - Particles and Fields
Particles and Fields
Eur. Phys. J. C 12, 609-626
DOI 10.1007/s100520000322

Measurement of the $\rm B^+$ and $\rm B^0$ lifetimes
and search for CP(T) violation
using reconstructed secondary vertices

The OPAL Collaboration

G.Abbiendi$^{\rm 2}$ - et al.

$^{\rm 2}$ Dipartimento di Fisica dell' Università di Bologna and INFN, 40126 Bologna, Italy

Received: 11 December 1998 / Published online: 3 February 2000 - © Springer-Verlag 2000 2000

Abstract
The lifetimes of the $\rm B^+$ and $\rm B^0$ mesons, and their ratio, have been measured in the OPAL experiment using 2.4 million hadronic $\rm Z^0$ decays recorded at LEP. ${\rm Z^0} \rightarrow {\rm b\overline{b}} $decays were tagged using displaced secondary vertices and high momentum electrons and muons. The lifetimes were then measured using well-reconstructed charged and neutral secondary vertices selected in this tagged data sample. The results are

\begin{eqnarray*}\tau_{B^+} & = & 1.643 \pm 0.037\pm 0.025 \rm\,ps \\ \tau_{B^0... ...s \\ \tau_{B^+}/ \tau_{B^0} & = & 1.079 \pm 0.064 \pm 0.041 \,, \end{eqnarray*}


where in each case the first error is statistical and the second systematic.
A larger data sample of 3.1 million hadronic $\rm Z^0$ decays has been used to search for CP and CPT violating effects by comparison of inclusive b and $\rm\overline{b}$ hadron decays. No evidence for such effects is seen. The CP violation parameter $\rm Re(\epsilon_B)$ is measured to be

\begin{displaymath}{\rm Re(\epsilon_B)} = 0.001 \pm 0.014 \pm 0.003 \end{displaymath}

and the fractional difference between b and $\rm\overline{b}$ hadron lifetimes is measured to be

\begin{displaymath}\left(\frac{\Delta\tau}{\tau}\right)_{\rm b} \equiv \frac{\rm... ... } hadron)} {\rm\tau (average)} = -0.001\pm 0.012\pm 0.008 \,. \end{displaymath}

Copyright Springer-Verlag 2000

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