ATLAS measurements of the azimuthal anisotropy in lead–lead collisions at $\sqrt{s_{NN}}=2.76$ TeV are shown using a dataset of approximately $7 \mu b^{-1}$ are shown using a dataset of approximately 7 < $p_{T}$ < 20 GeV and in the pseudorapidity range $\left | \eta \right |<2.5$. The anisotropy is characterized by the Fourier coefficients, $v_{n}$, of the charged-particle azimuthal angle distribution for n=2–4. The Fourier coefficients are evaluated using multi-particle cumulants calculated with the generating function method. Results on the transverse momentum, pseudorapidity and centrality dependence of the $v_{n}$ coefficients are presented. The elliptic flow, $v_{n}$, is obtained from the two-, four-, six- and eight-particle cumulants while higher-order coefficients, $v_{3}$ and $v_{4}$, are determined with two- and four-particle cumulants. Flow harmonics $v_{n}$ measured with four-particle cumulants are significantly reduced compared to the measurement involving two-particle cumulants. A comparison to $v_{n}$ measurements obtained using different analysis methods and previously reported by the LHC experiments is also shown. Results of measurements of flow fluctuations evaluated with multi-particle cumulants are shown as a function of transverse momentum and the collision centrality. Models of the initial spatial geometry and its fluctuations fail to describe the flow fluctuations measurements.
number of pulisher's sheets:
2
affiliation:
Wydział Fizyki, Astronomii i Informatyki Stosowanej : Instytut Fizyki im. Mariana Smoluchowskiego