ATLAS measurements of transverse and longitudinal flow decorrelations in Xe+Xe, Pb+Pb, and $p$+Pb collisions

Jun 3, 2020, 10:30 AM

Oral Presentation Initial State Parallel


Arabinda Behera (Stony Brook University (US))


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 measurements are performed using data from Xe+Xe collisions at 5.44 TeV, Pb+Pb collisions at 5.02 TeV, and $p$+Pb collisions at 5.02 and 8.16 TeV. The $v_{n}$ are measured up to $n=6$ using the two-particle correlations, multi-particle cumulants, and scalar product methods. The $v_{n}$ values are also performed using a non-flow subtraction technique that was developed for flow measurements in $pp$ and $p$+Pb collisions. This non-flow subtraction is found to have a significant effect on the measured $v_n$ at high-$p_T$ and in peripheral collisions. A universal scaling in the $p_{T}$ dependence of the $v_{n}$ is observed for both systems.
Measurements of correlations between the $v_n$ for different order $n$, studied with three- and four-particle mixed-harmonic cumulants, are also presented, and contributions to these correlations from ``centrality fluctuations'' are also discussed. Measurements of longitudinal flow decorrelations involving two- and four-particle correlations for $v_{2}$ and $v_{3}$ in Xe+Xe and $p$+Pb collisions are also presented and compared with the corresponding measurements in 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 is demonstrated.

Collaboration (if applicable) ATLAS
Track Initial State
Contribution type Contributed Talk

Primary authors

ATLAS Collaboration Lidija Zivkovic (Institute of physics Belgrade (RS))

Presentation materials