  An accurate knowledge of nuclear parton distribution functions (nPDFs) is an
essential ingredient of high energy physics calculations when the processes are
involving nuclei in the initial state. It is well known now that the prompt
photon production both in hadronic and nuclear collisions is a powerful tool
for exploring the parton densities in the nucleon and nuclei especially of the
gluon. In this work, we are going to perform a comprehensive study of the
isolated prompt photon production in $ p $-Pb collisions at backward rapidities
to find the best kinematic regions in which the experimental measurements have
most sensitivity to the nuclear modifications of parton densities. Most
emphasis will be placed on the antishadowing nuclear modification. To this aim,
we calculate and compare various quantities at different values of
center-of-mass energy covered by the LHC and also different rapidity regions to
realize which one is most useful.
