$B_s$ Mixing via $ψK^*$
The decay mode $B_s\toψ\overline{K}^*$ is suggested as a very good way to measure the $B_s$ mixing parameter $x_s$. These decays can be gathered using a $ψ\to\ell^+\ell^-$ trigger. This final state has a well resolved four track decay vertex, useful for good time resolution and background rejection.
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