Speaker
Description
ATLAS measurements of flow harmonics ($v_{n}$) and their fluctuations in Pb+Pb and Xe+Xe collisions covering a wide range of transverse momenta, pseudorapidity and collision centrality are presented. The $v_{n}$ are measured up to $n=7$ using the two-particle correlations, multi-particle cumulants and scalar product methods.The $v_{n}$ for $n$=2-7 is obtained with various correlation methods, together with a non-flow subtraction technique to improve the understanding of flow in peripheral region.A universal scaling in the $p_{T}$ dependence of the $v_{n}$ is observed for both systems. For the first time, longitudinal flow decorrelations involving two- and four-particle correlations for $v_{2}$ and $v_{3}$ are measured in Xe+Xe collisions and compared with results from Pb+Pb collisions.The four-particle decorrelation is found to not factorize as a product of two-particle decorrelations. The ability of such measurements to distinguish between different models of initial geometry and to reduce the uncertainty in determining the effective shear-viscosity to entropy-density ratio of the QGP are demonstrated.
