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 is fit using the running coupling BK equation. We show that it is possible to obtain a good fit of the HERA inclusive cross section also without an anomalous dimension in the initial condition. We argue that one must consistently use the proton transverse area as measured by a high virtuality probe in DIS also 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.