Open questions in QCD at high parton density

TL;DR

This paper reviews the current understanding of quantum chromodynamics (QCD) at high parton densities, highlights key open questions, and discusses how future electron-ion colliders can address these challenges to advance nuclear physics.

Contribution

It identifies the main unresolved issues in QCD at high parton density and emphasizes the potential of upcoming electron-ion colliders to provide comprehensive insights.

Findings

Highlights the importance of electron-ion colliders for QCD research.

Identifies key open questions in high-density QCD.

Suggests future experiments will significantly advance understanding.

Abstract

I present the state of our understanding of the QCD dynamics at play in the parton saturation regime of nuclear wave functions. I explain what are the biggest open questions in the field, their intrinsic interest, but also why is it important to answer them from the quark-gluon-plasma physicists' perspective. Focusing on those aspects that proton-nucleus collisions cannot investigate to a satisfactory degree, I show that future high-energy electron-ion colliders have the potential to address these questions, providing thorough answers in most cases, and exploratory measurements otherwise.