Nuclear shadowing and prompt photons at relativistic hadron colliders
  The production of prompt photons at high energies provides a direct probe of the dynamics of the strong interactions. In particular, one expect that it could be used to constrain the behavior of the nuclear gluon distribution in $pA$ and $AA$ collisions. In this letter we investigate the influence of nuclear effects in the production of prompt photons and estimate the transverse momentum dependence of the nuclear ratios $R_{pA} = {\frac{d\sigma (pA)}{dy d^2 p_T}} / A {\frac{d\sigma (pp)}{dy d^2 p_T}}$ and $R_{AA} = {\frac{d\sigma (AA)}{dy d^2 p_T}} / A^2 {\frac{d\sigma (pp)}{dy d^2 p_T}}$ at RHIC and LHC energies. We demonstrate that the study of these observables can be useful to determine the magnitude of the shadowing and antishadowing effects in the nuclear gluon distribution. 
C. Brenner Mariotto, V. P. Goncalves