  Utilizing the generalized factorization of twist-4 processes, we derive the
modified heavy quark fragmentation function after considering the gluon
radiation induced by multiple scattering in DIS. It is found that the mass
effects of heavy quark may reduce the gluon formation time and change the
medium size dependence of heavy quark energy loss. The radiative energy loss is
also significantly suppressed relative to a light quark due to the dead-cone
effect.
