Heavy flavor production in high energy hadron collisions is dominated by gluonic processes and so is a sensitive probe of the gluon structure function in the nucleon and its modification in nuclei. A study of heavy flavor production in p+p and d+Au collisions in various kinematic regions
presents an opportunity to probe cold nuclear medium effects; parton shadowing, color glass condensate, initial state energy loss, and coherent multiple scattering in final state interactions.
The PHENIX muon arms cover both forward and backward directions in the rapidity range of $1.2 < |\eta| < 2.4$. We investigate single muon production form open heavy flavor and light meson decay and the nuclear modification factor at forward and backward rapidity. The PHENIX preliminary results and current status of this analysis will be
presented.