Single inclusive particle production at high energy from HERA data to proton-nucleus collisions

Abstract

We study single inclusive hadron production in proton-proton and proton-nucleus collisions in the CGC framework. The parameters in the calculation are determined solely by standard nuclear geometry and by electron-proton deep inelastic scattering data, which are fit using the running coupling BK equation. We show that it also is possible to obtain a good fit of the HERA inclusive cross section without an anomalous dimension in the initial condition. We argue that one must consistently also use the proton transverse area as measured by a high virtuality probe in DIS for the single inclusive cross section in proton-proton and proton-nucleus collisions. We show that this leads to a midrapidity nuclear modification ratio ${R}_{pA}$ that approaches unity at high transverse momentum independently of $\sqrt{s}$, in contrast to most CGC calculations in the literature. We also present predictions for future forward ${R}_{pA}$ measurements at the LHC.