  Energy-energy-correlators (EEC's) are a promising observable to study the
dynamics of jet evolution in the quark-gluon plasma (QGP) through its imprint
on angular scales in the energy flux of final-state particles. We carry out the
first complete calculation of EEC's using realistic simulations of high-energy
heavy-ion collisions, and dissect the different dynamics underlying the final
distribution through analyses of jet propagation in a uniform medium. The EEC's
of $\gamma$-jets in heavy-ion collisions are found to be enhanced by the medium
response from elastic scatterings instead of induced gluon radiation at large
angles. In the meantime, EEC's are suppressed at small angles due to energy
loss and transverse momentum broadening of jet shower partons. These
modifications are further shown to be sensitive to the angular scale of the
in-medium interaction, as characterized by the Debye screening mass.
Experimental verification and measurement of such modifications will shed light
on this scale, and the short-distance structure of the QGP in heavy-ion
collisions.
