Photons from the Color Glass Condensate in p+A collisions

TL;DR

This paper presents the first next-to-leading order (NLO) calculation of photon production in proton-nucleus collisions within the Color Glass Condensate framework, revealing insights into gluon distributions and multi-gluon correlators.

Contribution

It extends previous leading-order results by including NLO processes, providing a more accurate description of photon production in p+A collisions.

Findings

NLO results dominate at central rapidities.

Photon spectrum is sensitive to nuclear gluon distribution at high momenta.

Numerical evaluation focuses on the annihilation process contribution.

Abstract

We report on a first NLO computation of photon production in p+A collisions at collider energies within the Color Glass Condensate framework, significantly extending previous LO results. At central rapidites, our result is the dominant contribution and probes multi-gluon correlators in nuclei. At high photon momenta, the result is directly sensitive to the nuclear gluon distribution. The NLO result contains two processes, the annihilation process and the process with $q\bar{q}$ pair and a photon in the final state. We provide a numerical evaluation of the photon spectrum from the annihilation process.