  We study three-hadron azimuthal angular correlations in high energy
proton-proton and central nucleus-nucleus collisions at RHIC and LHC at
mid-rapidity. We use the LO parton matrix elements for 2 \rightarrow 3
processes and include the effect of parton energy loss in the Quark-Gluon
Plasma using the modified fragmentation function approach. For the case when
the produced hadrons have either same or not too different momenta, we observe
two away side peaks at 2pi/3 and 4pi/3. We consider the dependence of the
angular correlations on energy loss parameters that have been used in studies
of single inclusive hadron production at RHIC. Our results on the angular
dependence of the cross section agree well with preliminary data by the PHENIX
collaboration. We comment on the possible contribution of 2 \rightarrow 3
processes to di-hadron angular correlations and how a comparison of the two
processes may help characterize the plasma further.
