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

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.