Mining for Gluon Saturation at Colliders

TL;DR

This paper reviews the theoretical and experimental progress in understanding gluon saturation in quantum chromodynamics at high energies, emphasizing the importance of future colliders like EIC and LHeC for advancing knowledge.

Contribution

It provides a comprehensive overview of the current state of gluon saturation research and advocates for the development of new electron-proton/ion colliders to deepen understanding.

Findings

Confirmed predictions of gluon saturation phenomena

Reviewed experimental evidence from high-energy collisions

Highlighted the need for future collider experiments

Abstract

Quantum chromodynamics (QCD) is the theory of strong interactions of quarks and gluons collectively called partons, the basic constituents of all nuclear matter. Its non-abelian character manifests in nature in the form of two remarkable properties: color confinement and asymptotic freedom. At high energies, perturbation theory can result in the growth and dominance of very gluon densities at small-x. If left uncontrolled, this growth can result in gluons eternally growing violating a number of mathematical bounds. The resolution to this problem lies by balancing gluon emissions by recombinating gluons at high energies : phenomena of gluon saturation. High energy nuclear and particle physics experiments have spent the past decades quantifying the structure of protons and nuclei in terms of their fundamental constituents confirming predicted extraordinary behavior of matter at extreme density and pressure conditions. In the process they have also measured seemingly unexpected phenomena. We will give a state of the art review of the underlying theoretical and experimental tools and measurements pertinent to gluon saturation physics. We will argue for the need of high energy electron-proton/ion colliders such as the proposed EIC (USA) and LHeC (Europe) to consolidate our knowledge of QCD in the small x kinematic domains.