Looking at saturation effects with η′ production in pA collisions

We compute the inclusive differential cross section production of the pseudo-scalar meson η′ in high-energy proton-nucleus (pA) collisions. We use an effective coupling between gluons and η′ meson to derive a reduction formula that relates the η′ production to a field-strength tensor correlator. We take into account saturation effects on the nucleus side by using the Color Glass Condensate formalism to evaluate this correlator. We derive new results for Wilson line - color charges correlators in the McLerran-Venugopalan model needed in the computation of η′ production. The unintegrated parton distribution functions are used to characterize the gluon distribution inside the proton. We show that the cross section is sensitive to saturation effects so it can be utilized to estimate the value of the saturation scale.