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

Abstract

Measurements of the 𝑝T-dependent flow vector fluctuations in Pb–Pb collisions at √𝑠NN=5.02TeV 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 𝑝T-dependent flow vector fluctuations at √𝑠NN=5.02TeV with two-particle correlations. Significant 𝑝T-dependent fluctuations of the 𝑉2 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 𝑝T-dependent fluctuations of 𝑉3 or V4 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 𝑝T, which might be biased by 𝑝T-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.