## Abstract

The distributions of event-by-event harmonic flow coefficients υ_{n} for n = 2-4 are measured in √s_{NN} = 2.76TeV Pb+Pb collisions using the ATLAS detector at the LHC. The measurements are performed using charged particles with transverse momentum pT > 0.5GeV and in the pseudorapidity range |η| < 2.5 in a dataset of approximately 7 μb-1 recorded in 2010. The shapes of the υ_{n} distributions suggest that the associated flow vectors are described by a two-dimensional Gaussian function in central collisions for υ_{2} and over most of the measured centrality range for υ_{3} and υ_{4}. Significant deviations from this function are observed for υ_{2} in mid-central and peripheral collisions, and a small deviation is observed for υ_{3} in mid-central collisions. In order to be sensitive to these deviations, it is shown that the commonly used multi-particle cumulants, involving four particles or more, need to be measured with a precision better than a few percent. The υ_{n} distributions are also measured independently for charged particles with 0.5 < p_{T} < 1 GeV and p_{T} > 1 GeV. When these distributions are rescaled to the same mean values, the adjusted shapes are found to be nearly the same for these two p_{T} ranges. The υ_{n} distributions are compared with the eccentricity distributions from two models for the initial collision geometry: a Glauber model and a model that includes corrections to the initial geometry due to gluon saturation effects. Both models fail to describe the experimental data consistently over most of the measured centrality range. Copyright CERN.

Original language | English (US) |
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Journal | Journal of High Energy Physics |

Volume | 2013 |

Issue number | 11 |

DOIs | |

State | Published - Nov 1 2013 |

## All Science Journal Classification (ASJC) codes

- Nuclear and High Energy Physics

## Keywords

- Event-by-event fluctuation
- Hadron-Hadron scattering
- Harmonic flow
- Heavy-ion collision
- Unfolding

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