Systematic study of flow vector fluctuations in sNN =5.02 TeV Pb-Pb collisions

Abstract

Measurements of the p T -dependent flow vector fluctuations in Pb–Pb collisions at s NN = 5.02 TeV using azimuthal correlations with the ALICE experiment at the Large Hadron Collider are presented. A four-particle correlation approach [ALICE Collaboration, ] is used to quantify the effects of flow angle and magnitude fluctuations separately. This paper extends previous studies to additional centrality intervals and provides measurements of the p T -dependent flow vector fluctuations at s NN = 5.02 TeV with two-particle correlations. Significant p T -dependent fluctuations of the V ⃗ 2 flow vector in Pb–Pb collisions are found across different centrality ranges, with the largest fluctuations of up to ∼ 15 % being present in the 5% most central collisions. In parallel, no evidence of significant p T -dependent fluctuations of V ⃗ 3 or V ⃗ 4 is found. Additionally, evidence of flow angle and magnitude fluctuations is observed with more than 5 σ significance in central collisions. These observations in Pb–Pb collisions indicate where the classical picture of hydrodynamic modeling with a common symmetry plane breaks down. This has implications for hard probes at high p T , which might be biased by p T -dependent flow angle fluctuations of at least 23% in central collisions. Given the presented results, existing theoretical models should be reexamined to improve our understanding of initial conditions, quark–gluon plasma properties, and the dynamic evolution of the created system. ©2024 CERN, for the ALICE Collaboration 2024 CERN