  Nuclear gluon modifications are the least constrained component of current
global fits to nuclear parton distributions, due to the inadequate constraining
power of presently available experimental data from nuclear deep inelastic
scattering and nuclear Drell-Yan lepton-pair production. A recent advance is
the use of observables from relativistic nucleus-nucleus collisions to
supplement the data pool for global fits. It is thus of interest to investigate
the sensitivity of various experimental observables to different strengths of
nuclear gluon modifications from large to small Bjorken $x$. In this work we
utilize three recent global fits with different gluon strengths to investigate
the sensitivity of three observables: nuclear modification factor,
pseudorapidity asymmetry, and charge ratio. We observe that both nuclear
modification factor and pseudorapidity asymmetry are quite sensitive to the
strength of gluon modifications in a wide pseudorapidity interval. The
sensitivity is greatly enhanced at LHC (Large Hadron Collider) energies
relative to that at RHIC (Relativistic Heavy Ion Collider). The charge ratio is
mildly sensitive only at large Bjorken x. Thus measurement of these observables
in proton-lead collisions at the LHC affords the potential to further constrain
gluon modifications in global fits.
