  We compare the azimuthal correlations arising from three and two hadron
production in high energy proton-proton and nucleus-nucleus collisions at
\sqrt{s_{NN}}=200 GeV, using the leading order matrix elements for two-to-three
and two-to-two parton-processes in perturbative QCD. We first compute the two
and three hadron production cross sections in mid-rapidity proton-proton
collisions. Then we consider Au + Au collisions including parton energy loss
using the modified fragmentation function approach. By examining the
geometrical paths the hard partons follow through the medium, we show that the
two away-side partons produced in two-to-three processes have in average a
smaller and a greater path length than the average path length of the away-side
parton in two-to-two processes. Therefore there is a large probability that in
the former processes one of the particles escapes while the other gets
absorbed. This effect leads to an enhancement in the azimuthal correlations of
the two-to-three with respect to the two-to-two parton-processes when comparing
to the same processes in proton-proton collisions since in average the particle
with the shortest path length looses less energy with respect to the away side
particle in two-to-two processes. We argue that this phenomenon may be
responsible for the shape of the away-side in azimuthal correlations observed
in mid-rapidity Au + Au collisions at RHIC.
