Collective Expansion at the LHC: selected ALICE anisotropic flow measurements

TL;DR

This paper reviews ALICE experiment measurements of anisotropic flow in heavy-ion collisions at the LHC, highlighting how collective expansion reveals properties of hot, dense nuclear matter through flow harmonic analysis.

Contribution

It provides a comprehensive overview of ALICE's flow harmonic measurements at the LHC, emphasizing new insights into the properties of quark-gluon plasma.

Findings

Flow harmonics increase with collision energy

Evidence of collective behavior in small systems

Constraints on the equation of state of nuclear matter

Abstract

The collective expansion of matter created in collisions of heavy-ions, ranging from collision energies of tens of MeV to a few TeV per nucleon pair, proved to be one of the best probes to study the detailed properties of these unknown states of matter. Collective expansion originates from the initial pressure gradients in the created hot and dense matter. These pressure gradients transform the initial spatial deformations and inhomogeneities of the created matter into momentum anisotropies of the final state particle production, which we call anisotropic flow. These momentum anisotropies are experimentally characterised by so-called flow harmonics. In this paper I review ALICE measurements of the flow harmonics at the CERN Large Hadron Collider and discuss some of the open questions.