Multiple parton scattering and induced parton energy loss is studied in
deeply inelastic scattering (DIS) off nuclei. The effect of multiple scattering
of a highly off-shell quark and the induced parton energy loss is expressed in
terms of the modification to the quark fragmentation functions. We derive such
modified quark fragmentation functions and their QCD evolution equations in DIS
using generalized factorization of higher twist parton distributions. We
consider double-hard, hard-soft parton scattering as well as their
interferences in the same framework. The final result, which depends on both
the diagonal and off-diagonal twist-four parton distributions in nuclei,
demonstrates clearly the Landau-Pomeranchuk-Migdal interference features and
predicts a unique nuclear modification of the quark fragmentation functions.Comment: Final version published in Nucl. Phys. A. 40 pages in RevTex with 15
postscript figure
