Measurement of reaction plane correlations in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$=2.76 TeV

A measurement of correlations between reaction-plane angles $\Phi_n$ for harmonic number $n$ in azimuth is presented as a function of centrality for Pb-Pb collisions at $\sqrt{s_{_{\mathrm{NN}}}}=2.76$ TeV, recorded by the ATLAS experiment at the LHC. These correlations are estimated from correlations of event-plane angles $\Psi_n$ reconstructed using the calorimeters over a large pseudorapidity range $|\eta|<4.8$, followed by a resolution correction that accounts for the dispersion of $\Psi_n$ relative to $\Phi_n$. Various correlators involving two or three reaction planes with acceptable resolution are measured. Significant positive correlation signals are observed for $4(\Phi_2-\Phi_4)$, $6(\Phi_2-\Phi_6)$, $6(\Phi_3-\Phi_6)$, $2\Phi_2+3\Phi_3-5\Phi_5$, $2\Phi_2+4\Phi_4-6\Phi_6$ and $-10\Phi_2+4\Phi_4+6\Phi_6$. However, the correlation signals are negative for $2\Phi_2-6\Phi_3+4\Phi_4$. These results may shed light on the patterns of the fluctuation of the created matter in the initial state as well as the subsequent hydrodynamic evolution.