  Multiple scattering, induced radiative energy loss and modified fragmentation
functions of a heavy quark in nuclear matter are studied within the framework
of generalized factorization in perturbative QCD. Modified heavy quark
fragmentation functions and energy loss are derived in detail with illustration
of the mass dependencies of the Landau-Pomeranchuk-Migdal interference effects
and heavy quark energy loss. Due to the quark mass dependence of the gluon
formation time, the nuclear size dependencies of nuclear modification of the
heavy quark fragmentation function and heavy quark energy loss are found to
change from a linear to a quadratic form when the initial energy and momentum
scale are increased relative to the quark mass. The radiative energy loss of
the heavy quark is also significantly suppressed due to limited cone of gluon
radiation imposed by the mass. Medium modification of the heavy quark
fragmentation functions is found to be limited to the large $z$ region due to
the form of heavy quark fragmentation functions in vacuum.
