Enhancement of prompt photons in ultrarelativistic proton-proton collisions from nonlinear gluon evolution at small-$x$

Abstract

In this paper we estimate the influence of nonlinear gluon evolution in the production of prompt photons at the LHC pp collider. We assume the validity of collinear factorization and consider the EHKQS parton distributions, which are solutions of the GLR-MQ evolution equations and describe quite well the DESY $ep$ HERA data, as input in our calculations. We find that both single and double photon production are enhanced for low-$p_T$ photons and central rapidities, while this effect is absent for the high-$p_T$ photons. The implications of this effect for the Quark-Gluon Plasma searches and for the QCD background to Higgs are also discussed.Comment: 4 pages, 4 figures. Version to be published in Physical Review