  We study the hydrodynamic response to jet quenching in expanding quark-gluon
plasma (QGP) and its signal in the resulting particle distribution. The ideal
hydrodynamic simulations of the $\gamma$-jet events in heavy-ion collisions are
performed in a full (3 + 1)-dimensional setup. The jet-induced Mach cone and
the radial expansion of the background mutually push and distort each other. As
a result, the particle emission is suppressed in the direction in which the
radial flow is pushed back by the Mach cone when the jet path is an off-central
one. This is the direct signal of hydrodynamic response to the jetand,
moreover, includes information about the jet path in the expanding QGP fluid.
