Measurement of event plane correlations in Pb-Pb collisions with the ATLAS detector

Recently harmonic flow coefficients $v_1-v_6$ have been measured in heavy-ion collisions at LHC. The magnitude of these coefficients and their centrality dependence suggest that they are associated with the various shape components in the initial geometry, arising from fluctuations of the participating nucleons in the overlap region. The orientation of these harmonics (event plane or $Phi_n$) are generally correlated due to the correlations between the original shape components in the initial geometry; the correlations between event plane can also be generated dynamically during the hydrodynamic evolution of the medium. We present first measurements of various event plane correlations involving $Phi_2$ to $Phi_6$ in Pb-Pb collisions at the LHC. The large acceptance of the ATLAS EM calorimeters, covering $-5<eta<5$, allows for a precise measurement of these correlations. The procedure for obtaining these correlations and the physics implication of the results are discussed.