  The experimental results on transverse momentum azimuthal hadron correlations
at RHIC have opened a rich field for parton energy loss analysis in heavy-ion
collisions. Recently, a considerable amount of work has beendevoted to study
the shapes of the ``away-side'' jet which exhibit an interesting and unexpected
``double hump'' structure not observed in the analogous treatment of $pp$ data.
Driven by the possibility that the latter result might just mean that such
structure exists already in the case of $pp$ collisions, but that its relative
intensity could be small, here we use the Event Shape Analysis to show that it
is possible to identify and select well defined event topologies in $pp$
collisions, among which, a double hump structure for the away-side jet emerges.
Using two shape parameters, the sphericity in the transverse plane and the
recoil to analyze a sample of PYTHIA generated $pp$ collisions at
$\sqrt{s_{NN}}=200$ GeV, we show that this structure corresponds to two jets
emitted in the backward hemisphere. Finally, we show that Q-PYTHIA
qualitatively reproduces the decrease in the yield of dijet events and the
increase of the double hump structure in the away side observed in heavy ion
collisions. The implications for the treatment of parton energy loss in
heavy-ion collisions are discussed
