Initial conditions in AA and pA collisions

TL;DR

This paper reviews the initial conditions and early evolution of quark-gluon plasma in heavy ion collisions, emphasizing classical gluon fields and gluon saturation effects, especially in small systems showing collective behavior.

Contribution

It provides recent insights into initial matter production and thermalization within the gluon saturation framework, highlighting the role of classical gluon fields in small and large systems.

Findings

Initial stages dominated by classical gluon fields.

Signatures of collective behavior in small systems.

Advances in understanding thermalization processes.

Abstract

A full understanding of the spacetime evolution of the QCD matter created in a heavy ion collision requires understanding the properties of the initial stages. In the weak coupling picture these are dominated by classical gluon fields, whose properties can also be studied via the scattering of dilute probes off a high energy hadron or nucleus. A particular challenge is understanding small systems, where LHC data is also showing signs of collective behavior. We discuss some recent results of on the initial matter production and thermalization in heavy ion collisions, in particular in the gluon saturation framework.