Relativistic Nucleus-Nucleus Collisions and the QCD Matter Phase Diagram

TL;DR

This review discusses the properties and phases of QCD matter, focusing on the transition from confined hadrons to the deconfined quark-gluon plasma in relativistic nucleus-nucleus collisions.

Contribution

It provides a comprehensive overview of the current understanding of QCD matter phases, especially the quark-gluon plasma, in high-energy nuclear collisions.

Findings

Evidence for QGP formation in heavy-ion collisions

Characteristics of confinement and deconfinement transitions

Insights into the QCD phase diagram

Abstract

This review will be concerned with our knowledge of extended matter under the governance of strong interaction, in short: QCD matter. Strictly speaking, the hadrons are representing the first layer of extended QCD architecture. In fact we encounter the characteristic phenomena of confinement as distances grow to the scale of 1 fm (i.e. hadron size): loss of the chiral symmetry property of the elementary QCD Lagrangian via non-perturbative generation of "massive" quark and gluon condensates, that replace the bare QCD vacuum. However, given such first experiences of transition from short range perturbative QCD phenomena (jet physics etc.), toward extended, non perturbative QCD hadron structure, we shall proceed here to systems with dimensions far exceeding the force range: matter in the interior of heavy nuclei, or in neutron stars, and primordial matter in the cosmological era from electro-weak decoupling (10^-12 s) to hadron formation (0.5 10^-5 s). This primordial matter, prior to hadronization, should be deconfined in its QCD sector, forming a plasma (i.e. color conducting) state of quarks and gluons: the Quark Gluon Plasma (QGP).