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 $Deltaphi$ 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 $sigma_{cbar{c}} =$ 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 $Deltaphi = pi$ is dominantly from the leading order contributions (gluon fusion), while higher order processes (flavor excitation and gluon splitting) contribute to the yield at all $Deltaphi$. We observe a suppression in the pair yield per collision in $d$+Au. We find the pair yield suppression factor for $2.7<Deltaphi<3.2$ rad is $J_{dA}$ = 0.433 $pm$ 0.087 (stat) $pm$ 0.135 (syst), indicating cold nuclear matter modification of $cbar{c}$ pairs.
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