The e+A programme at a future Electron-Ion Collider facility

TL;DR

The paper discusses the scientific potential of an electron-ion collider (e+A) to explore high gluon densities at small x, which is crucial for understanding nuclear wave functions and the quark-gluon plasma.

Contribution

It highlights the importance of e+A collisions at a future collider for studying gluon saturation and comparing with A+A results, proposing a new experimental avenue.

Findings

e+A collisions can probe gluon saturation effects

Comparison with A+A collisions can reveal new states of matter

Understanding gluon interactions is essential for interpreting collider results

Abstract

At small x, the gluon distribution dominates the nuclear wave function. The increase needs to be tamed in avoid violating unitarity constraints. The most efficient way to study this in colliders is through e+A collisions as the nucleus is an efficient amplifier of the physics of high gluon densities. To this end, there are proposals to build an e+A machine in the USA which would operate over a large range of energies and masses. These studies would also allow an in-depth comparison to A+A collisions where recent results have given tantalising hints of a new state of matter produced with partonic degrees of freedom. As gluon interactions are the dominant source of hard probes, they themselves must be understood before the results are explained quantitatively.