${{\mathit B}^{0}}-{{\overline{\mathit B}}^{0}}$ 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 average and rescaling were performed by the Heavy Flavor Averaging Group (HFLAV) and are described at https://hflav.web.cern.ch/. 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 ${{\mathit \Upsilon}{(4S)}}$.

$\bf{ 0.769 \pm0.004}$ OUR EVALUATION
Conservation Laws:
$\Delta \mathit B$ = 2 VIA MIXING