2018 Impact factor 4.843
Particles and Fields
Eur. Phys. J. C 5, 195-203
DOI 10.1007/s100529800901

Measurement of the ${\rm\bf B_{\bf d}^{\bf 0}-
 {\bf \bar{B}}_{\bf d}^{\bf 0}}$ oscillation frequency

The L3 Collaboration
M.Acciarri27 - et al.

27 INFN-Sezione di Milano, I-20133 Milan, Italy

Received: 20 February 1998 / Revised version: 23 March 1998 / Published online: 12 August 1998

Abstract
Time-dependent \ensuremath{{\rm B^{0}}\mbox{-}\bar{{\rm B}}^{0}} mixing is studied using about two million hadronic Z decays registered by L3 in 1994 and 1995. For this study three techniques are used. Tagging of the b-quark charge at decay time is performed by identifying leptons from semileptonic B decays. The flavour of the b quark at production time is determined from the charge of the lepton in the opposite hemisphere or by using a jet-charge technique. The proper time of the B-particle decay is obtained by reconstructing the production and decay vertices or by a measurement of the lepton impact parameter. The combined result for the frequency of \ensuremath{{\rm B_d^0}} meson oscillations is

\begin{displaymath}
\ensuremath{\Delta m_d}= 0.444 \pm 0.040 \ {\rm ps}^{-1}.
 \end{displaymath}


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