  A high energy jet that propagates in a dense medium generates a cascade of
partons that can be described as a classical branching process. A simple
generating functional for the probabilities to observe a given number of gluons
at a given time is derived. This is used to obtain an evolution equation for
the inclusive one-gluon distribution, that takes into account the dependence
upon the energy and the transverse momentum of the observed gluon. A study of
the explicit transverse momentum dependence of the splitting kernel leads us to
identify large corrections to the jet quenching parameter.
