  The influence of final-state radiation (FSR) of heavy quarks on observables
in high-energy proton-proton collisions is studied. The transverse momentum
correlation of D and Dbar mesons, which have been emitted with an azimuthal
difference angle close to 180 degrees, is identified as an observable which is
sensitive to the FSR process. We demonstrate this by performing calculations
with the EPOS3+HQ model and with the event generator Pythia 6. The initial
symmetric pT = pT' correlation for back-to-back pairs does not completely
vanish in EPOS3+HQ, neither for the final DDbar pairs nor for the ccbar pairs
before hadronisation. Also a significant difference in the shape of the
correlation distribution for EPOS3+HQ and Pythia 6 is observed. Therefore,
particle correlations in pp data offer the possibility to study several aspects
of energy loss in heavy-ion collisions.
