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April 24, 2026

Evidence for the collective nature of radial flow in Pb+Pb collisions with the ATLAS detector

Key Points

The aim is to investigate the collective nature of radial flow fluctuations in heavy-ion collisions.
Analysis of transverse momentum differential observable v0(pT)
Measurements conducted in Pb+Pb collisions at √sNN = 5.02TeV
Comparison with hydrodynamic model calculations
Identification of three signatures of collective behavior: factorization, long-range correlations, and a centrality-independent shape.
Findings show v0(pT) is sensitive to the bulk viscosity of the QGP.

Abstract

In heavy-ion collisions, the isotropic radial expansion of the formed Quark-Gluon Plasma (QGP) has been studied using its influence on other experimental observables. This proceeding summarizes the first direct evidence for the collective nature of radial flow fluctuations, using a transverse momentum (pT) differential observable, v0(pT), measured in Pb+Pb collisions at √sNN = 5.02TeV by the ATLAS Collaboration 1. The measurement reveals three key signatures of the collective behavior of radial flow: factorization, longrange pseudorapidity correlations, and a centrality-independent shape. Comparisons with hydrodynamic model calculations show that v0(pT) is highly sensitive to the bulk viscosity of the QGP.

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