Measurement of the $B^0-{\bar{B}}^0$ mixing rate with $B^0({\bar{B}}^0)\to D^{\ast \mp }{\pi }^{\pm }$ partial reconstruction

Abstract

We report a measurement of the $B^0-{\bar{B}}^0$ mixing parameter $\Delta m_d$ based on a $29.1\mathrm{f}{\mathrm{b}}^{-1}$ sample of ${\rm Y}(4S)$ resonance decays collected by the Belle detector at the KEKB asymmetric $e^{+}{e}^{-}$ collider. We use events with a partially reconstructed $B^0({\bar{B}}^0)\to D^{\ast \mp }{\pi }^{\pm }$ candidate and where the flavor of the accompanying $B$ meson is identified by the charge of the lepton from a $B^0({\bar{B}}^0)\to X^{\mp }{\ell }^{\pm }\nu$ decay. The proper-time difference between the two $B$ mesons is determined from the distance between the two decay vertices. From a simultaneous fit to the proper-time distributions for the same-flavor ($B^0({\bar{B}}^0)$, ${\ell }^{\pm }$) and opposite-flavor ($B^0({\bar{B}}^0)$, ${\ell }^{\mp }$) event samples, we measure the mass difference between the two mass eigenstates of the neutral $B$ meson to be $\Delta m_d$= $(0.509\pm 0.017(\mathrm{stat})\pm 0.020(\mathrm{syst}))\mathrm{p}{\mathrm{s}}^{-1}$.

16 pages, 14 figures

References in corpus (2)

• Electron Identification in Belle
• Measurement of Inclusive Production of Neutral Pions from Upsilon(4S) Decays

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