  We report on measurements of differential $\mu - {\bar b}$ cross sections,
where the muon is from a semi-leptonic $b$ decay and the ${\bar b}$ is
identified using precision track reconstruction in jets. The semi-differential
correlated cross sections, d$\sigma$/d$\Et^{{\bar b}}$, d$\sigma$/d$\pt^{{\bar
b}}$, and d$\sigma$/d$\delta\phi(\mu - {\bar b})$ for $\pt^{\mu}>$~9 GeV/c,
$|\eta^{\mu}|<$~0.6, $\Et^{{\bar b}}>$~10 GeV, $|\eta^{{\bar b}}|<$~1.5, are
presented and compared to next-to-leading order QCD calculations.
