Gluon saturation effects at forward rapidities at LHC in pp collisions

TL;DR

This paper explores gluon saturation effects in proton-proton collisions at the LHC, highlighting the potential of forward rapidity measurements, especially direct photon production, to probe saturation phenomena.

Contribution

It demonstrates the sensitivity of forward rapidity measurements to gluon saturation effects and compares different saturation models using the color-dipole approach.

Findings

Gluon saturation effects are most detectable at very forward rapidities.

Discrepancies among saturation models can be a factor of 2-3.

The ratio of direct-photon to pion production can reach 20-10 at =7-8.

Abstract

We investigate hadrons and direct photon production in pp collisions at the LHC energy within the color-dipole approach. We show that greatest sensitivity to gluon saturation effects is reached at very forward rapidities in pp collisions at LHC (\sqrt{s}=14 TeV). The discrepancies among various saturation models (fitted to HERA data) results can be about a factor of 2-3 at forward rapidities. We found that the ratio of direct-photon to pion production can be about 20-10 at forward rapidities \eta=7-8. Therefore, direct photon production at forward rapidities should provide a rather clean probe as the background from radiative hadronic decays is significantly suppressed.