Prompt photon production in proton–nucleus collisions at LHC: a comparison among color dipole models*

Abstract

The nuclear modification factor for prompt photon production in proton-nucleus (p+A) collisions are investigated within the color dipole formalism. By means of the Glauber-Gribov approach, the nuclear effects are studied in various rapidity bins with the evolution equation based saturation models and the phenomenological dipole models. The theoretical results are compared with the experimental data provided by PHENIX, ATLAS and CMS Collaborations. At forward rapidity and midrapidity, a reasonable agreement with the experimental data is shown for the theoretical results with the modified Kharzeev, Levin and Nardi (KLN) model, and the Kowalski and Teaney (KT) model. Then, we analyze the influence of the initial state energy loss effect on the nuclear modification factor and find that it is obvious only at backward rapidity together with small $p_{\mathrm{T}}$. Finally, the theoretical results are also compared with those of JETPHOX Monte Carlo program and the predictive results for the LHCb at very forward rapidities are presented.