Observations on dA scattering at forward rapidities
V. Guzey, M. Strikman, W. Vogelsang
TL;DR
Addressing the BRAHMS forward-rapidity suppression in RdAu for hadron production, the paper investigates whether leading-twist shadowing and standard pQCD dynamics can explain the data. Using full NLO pQCD calculations for inclusive hadron production and an explicit treatment of the h^− selection, the authors quantify the impact of isospin and the enhancement of the pp baseline. They analyze the relevant parton momentum fractions, showing that the dominant contributions come from $x_{\mathrm{Au}} > 0.02$ at forward rapidity. They also show that very small-$x$ regions are not the main driver and that conventional shadowing alone cannot fully account for the suppression, providing guidance for interpreting future forward-rapidity measurements.
Abstract
We point out that the suppression in the ratio R_dAu recently observed by the BRAHMS collaboration in forward scattering is stronger than usually appreciated. This is related to the fact that at forward rapidities BRAHMS measures negatively charged hadrons and that R_dAu is defined from the ratio of dA and pp scattering cross sections. We also investigate the influence of standard shadowing on R_dAu, and the typical values of partonic momentum fractions relevant in forward scattering. We find that x_Au > 0.02 dominate in the cross section.