  We report $e^\pm-\mu^\mp$ pair yield from charm decay measured between
midrapidity electrons ($|\eta|<0.35$ and $p_T>0.5$ GeV/$c$) and forward
rapidity muons ($1.4<\eta<2.1$ and $p_T>1.0$ GeV/$c$) as a function of
$\Delta\phi$ in both $p$$+$$p$ and in $d$+Au collisions at
$\sqrt{s_{_{NN}}}=200$ GeV. Comparing the $p$$+$$p$ results with several
different models, we find the results are consistent with a total charm cross
section $\sigma_{c\bar{c}} =$ 538 $\pm$ 46 (stat) $\pm$ 197 (data syst) $\pm$
174 (model syst) $\mu$b. These generators also indicate that the back-to-back
peak at $\Delta\phi = \pi$ is dominantly from the leading order contributions
(gluon fusion), while higher order processes (flavor excitation and gluon
splitting) contribute to the yield at all $\Delta\phi$. We observe a
suppression in the pair yield per collision in $d$+Au. We find the pair yield
suppression factor for $2.7<\Delta\phi<3.2$ rad is $J_{dA}$ = 0.433 $\pm$ 0.087
(stat) $\pm$ 0.135 (syst), indicating cold nuclear matter modification of
$c\bar{c}$ pairs.
