  Using the Drell-Yan process in hadron-nucleus collisions and deeply inelastic
lepton-nucleus scattering (DIS) as examples, I show that the transverse
momentum broadening can be expressed in terms of four-parton correlation
functions. I argue that jet broadening in DIS provide an excellent measurement
of the four-parton correlation functions and a test of QCD treatment of the
multiple scattering.
