Measurement of the ${B}^{0}\mathrm{\text{\ensuremath{-}}}{\overline{B}}^{0}$ Mixing Parameter $\ensuremath{\Delta}{m}_{d}$ using Semileptonic ${B}^{0}$ Decays

Measurement of the $B^{0} − {\bar{B}}^{0}$ Mixing Parameter $Δ m_{d}$ using Semileptonic $B^{0}$ Decays

K. Hara et al. (Belle Collaboration)

Phys. Rev. Lett. 89, 251803 – Published 3 December 2002

Abstract

We present a measurement of the $B^{0} − {\bar{B}}^{0}$ mixing parameter $Δ m_{d}$ using neutral $B$ meson pairs in a $29.1 f b^{- 1}$ data sample collected at the $Υ (4 S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+} e^{-}$ collider. We exclusively reconstruct one neutral $B$ meson in the semileptonic $B^{0} \to D^{* -} ℓ^{+} ν$ decay mode and identify the flavor of the accompanying $B$ meson from its decay products. From the distribution of the time intervals between the two flavor-tagged $B$ meson decay points, we obtain $Δ m_{d} = (0.494 \pm 0.012 \pm 0.015) {p s}^{- 1}$ , where the first error is statistical and the second error is systematic.