Speaker
Description
The fourth-order cumulant of quadrangular flow ($\bf{v}_4$), $C_4\{4\}$, exhibits a distinct trend in Pb-Pb collisions at the LHC energy [1]: negative for 0-20% centrality, changes sign and becomes positive around 20-30% centrality, and remains positive throughout the remaining centrality range. This measurement, made over half a decade ago, remains unexplained. We attribute the observed sign change to a complex interplay between the linear and non-linear components of $\bf{v}_4$. We discover that the linear component has a significant reaction plane component, a novel insight that successfully reproduces the striking trend of $C_4\{4\}$ using a Gaussian model of eccentricity fluctuations. Finally, we discuss the potential for similar sign-changing behavior across different collision systems.
[1] M. Aaboud et al. (ATLAS), JHEP 01, 051 (2020).
| Category | Theory |
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