Diphoton production in high-energy p+A collisions

TL;DR

This paper models diphoton production in high-energy proton-nucleus collisions, highlighting how correlations at low transverse momenta reveal saturation effects in the nuclear target.

Contribution

It introduces a framework combining the Color-Glass-Condensate model with the parton model to analyze diphoton production and correlations in p+A collisions.

Findings

Diphoton correlations at low transverse momentum are sensitive to saturation effects.

Back-to-back correlations are stronger in the fragmentation component than in the direct component.

The study provides predictions for diphoton production at LHC energies.

Abstract

We consider semi-inclusive diphoton+jet and inclusive diphoton production in high-energy proton-nucleus collisions, treating the target nucleus as a Color-Glass-Condensate and the projectile proton in the parton model. We obtain the prompt diphoton production cross-section in terms of fragmentation and direct contributions. The fragmentation part is given in terms of single-photon and double-photon fragmentation functions. We study prompt, direct and fragmentation diphoton correlations in p+p and p+A collisions at the LHC, and show that at low values of transverse momenta of the produced photon pair, these correlations are sensitive to saturation effects. We show that back-to-back (de)-correlations in prompt diphoton production are stronger in fragmentation part than in the direct one.