  The effect of multiple scatterings on the propagation of hard partonic jets
in a dense nuclear medium is studied in the framework of deep-inelastic
scattering (DIS) off a large nucleus. Power counting arguments based on the
Glauber improved Soft-Collinear-Effective-Theory are used to identify the class
of leading power corrections to the process of a single parton traversing the
extended medium without emission. It turns out that the effect of longitudinal
drag and diffusion (often referred to as straggling) is as important as
transverse scattering, when relying solely on power counting arguments. With
the inclusion of momentum exchanges in both transverse and longitudinal
directions between the traversing hard parton and the constituents of the
medium, we derive a differential equation for the time (or distance) evolution
of the hard parton momentum distribution. Keeping up to the second order in a
momentum gradient expansion, this equation describes in-medium evolution of
hard jets which experience longitudinal drag and diffusion plus the transverse
broadening caused by multiple scatterings from the medium.
