  The most suitable way to study the jet quenching as a function of distance
traversed is varying the impact parameter b of ultrarelativistic
nucleus-nucleus collision (initial energy density in nuclear overlapping zone
is almost independent of b up to b R_A). It is shown that b-dependences of
medium-induced radiative and collisional energy losses of a hard parton jet
propagating through dense QCD-matter are very different. The experimental
verification of this phenomenon could be performed for a jet with non-zero cone
size basing on essential difference between angular distributions of
collisional and radiative energy losses.
