Ultra-peripheral nucleus-nucleus collisions (UPC) are mediated by strong
electromagnetic fields, offering the opportunity to study photon-nucleus processes at RHIC.
Coherent $J/\psi$ photoproduction is of particular interest for its sensitivity
to nuclear gluon distribution. The $J/\psi$ mesons are heavy enough to be described
by perturbative Quantum Chromodynamics (pQCD), where coherent cross section, at the first order, is proportional to the square of the nuclear gluon distribution.
This makes coherent $J/\psi$ cross section an ideal probe to phenomena of gluon saturation
and nuclear gluon shadowing.
Here we present a brief overview of the topic and preliminary results of exclusive
coherent $J/\psi$ photoproduction in Au+Au UPC at \energyAuAu\ at central rapidity $|y|<1$,
where the photoproduction was tagged at the trigger level
by forward neutrons emitted as a result of electromagnetic excitation of the nuclei.