# Nuclear gluons at RHIC in a multi-observable approach

## TL;DR

This paper investigates measuring nuclear gluon distributions at RHIC using multiple observables like Drell-Yan, dijet, and photon-jet processes, highlighting the potential of forward rapidity measurements and collider flexibility.

## Contribution

It introduces a multi-observable approach to probe nuclear gluons at RHIC, including methods to reduce experimental uncertainties and utilize different ion beams for comprehensive measurements.

## Key findings

- Drell-Yan is an effective probe of small-x gluons.
- Normalization uncertainties can be mitigated using complementary observables.
- RHIC's flexibility enables studying A-dependence of gluon distributions.

## Abstract

We explore the possibility of measuring nuclear gluon distributions at the Relativistic Heavy-Ion Collider (RHIC) with $\sqrt{s}=200 \, {\rm GeV}$ proton-nucleus collisions. In addition to measurements at central rapidity, we consider also observables at forward rapidity, consistent with proposed upgrades to the experimental capabilities of STAR and sPHENIX. The processes we consider consist of Drell-Yan dilepton, dijet, and direct photon-jet production. The Drell-Yan process is found to be an efficient probe of gluons at small momentum fractions. In order to fully utilize the potential of Drell-Yan measurements we demonstrate how the overall normalization uncertainty present in the experimental data can be fixed using other experimental observables. An asset of the RHIC collider is its flexibility to run with different ion beams, and we outline how this ability could be taken advantage of to measure the $A$ dependence of gluon distributions for which the current constraints are scarce.