  The collimation of average multiplicity inside quark and gluon jets is
investigated in perturbative QCD in the modified leading logarithmic
approximation (MLLA). The role of higher order corrections accounting for
energy conservation and the running of the coupling constant leads to smaller
multiplicity collimation as compared to leading logarithmic approximation (LLA)
results. The collimation of jets produced in heavy-ion collisions has also been
explored by using medium-modified splitting functions enhanced in the infrared
sector. As compared to elementary collisions, the angular distribution of the
jet multiplicity is found to broaden in QCD media at all energy scales.
