#### ${{\mathit B}^{0}}-{{\overline{\mathit B}}^{0}}$ MIXING PARAMETERS

For a discussion of ${{\mathit B}^{0}}-{{\overline{\mathit B}}^{0}}$ mixing see the note on “${{\mathit B}^{0}}-{{\overline{\mathit B}}^{0}}$ Mixing” in the ${{\mathit B}^{0}}$ Particle Listings above.
${{\mathit \chi}_{{{d}}}}$ is a measure of the time-integrated ${{\mathit B}^{0}}-{{\overline{\mathit B}}^{0}}$ mixing probability that a produced ${{\mathit B}^{0}}({{\overline{\mathit B}}^{0}}$) decays as a ${{\overline{\mathit B}}^{0}}({{\mathit B}^{0}}$). Mixing violates $\Delta \mathit B{}\not=$2 rule.
${{\mathit \chi}_{{{d}}}}$ = ${\mathit x{}^{2}_{\mathit d}\over 2(1+\mathit x{}^{2}_{\mathit d})}$

$\mathit x_{\mathit d}$ = ${\Delta {\mathit m}_{{{\mathit B}^{0}}}\over \Gamma _{{{\mathit B}^{0}}}}$ = (${\mathit m}_{{{\mathit B}_{{{H}}}^{0}}}$ $-$ ${\mathit m}_{{{\mathit B}_{{{L}}}^{0}}}){\mathit \tau}_{{{\mathit B}^{0}}}$ ,
where $\mathit H$, $\mathit L$ stand for heavy and light states of two ${{\mathit B}^{0}}$ $\mathit CP$ eigenstates and ${\mathit \tau}_{{{\mathit B}^{0}}}$ = ${1\over 0.5 (\Gamma _{{{\mathit B}_{{{H}}}^{0}}}+\Gamma _{{{\mathit B}_{{{L}}}^{0}}})}$.

#### $\mathit x_{\mathit d}$ = $\Delta {\mathit m}_{{{\mathit B}^{0}}}/\Gamma _{{{\mathit B}^{0}}}$

“OUR EVALUATION” is an average using rescaled values of the data listed below. The averaging/rescaling procedure takes into account correlations between the measurements and includes $\Delta {\mathit m}_{{{\mathit d}}}$ calculated from ${{\mathit \chi}_{{{d}}}}$ measured at ${{\mathit \Upsilon}{(4S)}}$.

VALUE
 $\bf{ 0.7697 \pm0.0035}$ OUR EVALUATION  $~~$(Produced by HFLAV)
Conservation Laws:
$\Delta \mathit B$ = 2 VIA MIXING