Gluon shadowing in nuclei and the role of the c c g state in the coherent photoproduction of J/ψ in nucleus-nucleus collisions

In this brief note, we confront our results on diffractive photoproduction of J/ψ mesons with the putative gluon shadowing ratio defined as Rg= √σ(γ A → J/ψ A)/σIA., where σIA is the result in impulse approximation. Building on our earlier description of the process in the color-dipole approach, where we took into account the rescattering of c c states only, we demonstrate that the inclusion of c c g-Fock states improves the description at small x commonly associated with gluon shadowing.