For decades, hadron structure research has progressed toward probing the behavior of constituent quarks and gluons (partons) at smaller and smaller fractions (x) of their parent hadron's momentum. At sufficiently small x, this behavior is expected to transition to saturation, a condition where parton self-interactions and multiple scatterings become significant.

High-energy proton-nucleus collisions at RHIC and the LHC provide the best available testing ground for the saturation model. However, producing precise numerical predictions from the model is quite difficult. Recent work has shown that accurate predictions require including next-to-leading order corrections to the cross section, some of which are quite subtle and require careful work to account for. Also, numerical evaluation of the resulting formulas presents several technical challenges, especially with the extreme parameters of the LHC.

In this talk I'll present the results from our recent paper which addresses both sets of difficulties. With the incorporation of exact kinematical effects, we now have the cross section for inclusive hadron production complete to one-loop order. And having addressed the technical challenges of numerical integration, we are able to produce accurate results for both RHIC and LHC parameter sets. In both cases, with appropriate choices of the input parameters, our results agree cleanly with the available experimental data over the transverse momentum range where we expect the model to be effective.

Host: Prof. Xiangdong Ji