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

Measurements of the p(T)-dependent flow vector fluctuations in Pb-Pb collisions at root 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, Phys. Rev. C 107, L051901 (2023)] 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 root S-NN = 5.02 TeV with two-particle correlations. Significant p(T)-dependent fluctuations of the (V) over right arrow (2) flow vector in Pb-Pb collisions are found across different centrality ranges, with the largest fluctuations of up to similar to 15% being present in the 5% most central collisions. In parallel, no evidence of significant p(T)-dependent fluctuations of (V) over right arrow (3) or (V) over right arrow (4) is found. Additionally, evidence of flow angle and magnitude fluctuations is observed with more than 5 sigma 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.