  In this paper, we study the production of isolated-photon plus a jet in $pp$
and $PbPb$ collisions, which can be used as an important probe to the jet
transport property in quark gluon plasma created in heavy ion collisions.
Normally, there are two types of observables associated with the production of
isolated-photon plus a jet, namely, the azimuthal angular correlation and the
transverse momentum imbalance. To understand both observables in the full
kinematical region, we need to employ the perturbative QCD calculation, which
takes into account the hard splitting of partons, together with the Sudakov
resummation formalism, which resums soft gluon splittings. Furthermore, by
introducing energy-loss into the system, we calculate the enhancement of the
momentum imbalance distribution for $AA$ as compared to $pp$ collisions and
make predictions for future unfolded experimental data. In addition, in order
to extract the jet transport coefficient more precisely in our numerical
calculation, we also distinguish quark jets from gluon jets, since they
interact with quark gluon plasma with different strengths. This work provides a
reliable theoretical tool for the calculation of the gamma-jet correlation,
which can lead us to a more precise extraction of the jet transport coefficient
in relativistic heavy-ion collisions.
