QCD in heavy ion collisions

TL;DR

This paper provides an overview of the theoretical frameworks and phenomena related to the partonic states of QCD matter in ultrarelativistic heavy ion collisions, highlighting recent experimental observations at RHIC and LHC.

Contribution

It introduces and explains the effective theories describing the color glass condensate, glasma, and quark-gluon plasma, connecting them to experimental phenomena.

Findings

Observation of particle suppression and azimuthal correlations

Analysis of energy and centrality dependence of multiplicities

Insights into jet quenching and dijet asymmetry

Abstract

These lectures provide a modern introduction to selected topics in the physics of ultrarelativistic heavy ion collisions which shed light on the fundamental theory of strong interactions, the Quantum Chromodynamics. The emphasis is on the partonic forms of QCD matter which exist in the early and intermediate stages of a collision -- the colour glass condensate, the glasma, and the quark-gluon plasma -- and on the effective theories that are used for their description. These theories provide qualitative and even quantitative insight into a wealth of remarkable phenomena observed in nucleus-nucleus or deuteron-nucleus collisions at RHIC and/or the LHC, like the suppression of particle production and of azimuthal correlations at forward rapidities, the energy and centrality dependence of the multiplicities, the ridge effect, the limiting fragmentation, the jet quenching, or the dijet asymmetry.