Probing non-linearity of higher order anisotropic flow in Pb-Pb collisions

Abstract

The second and the third order anisotropic flow, V2 and V3, are etermined by the corresponding initial spatial anisotropy coefficients, ε2 and ε3, in the initial density distribution. On the contrary, the higher order anisotropic flow Vn (n > 3), in addition to their dependence on the same order initial anisotropy coefficient εn, have a significant contribution from lower order initial anisotropy coefficients, which leads to mode-coupling effects. In this contribution, we present the investigations on linear and non-linear modes √ in higher order anisotropic flow (V4, V5 and V6) in Pb–Pb collisions at √sNN = 2.76 TeV using the ALICE detector at the Large Hadron Collider (LHC). A significant contribution from a nonlinear mode is observed. A new observable, the non-linear response coefficient, is measured as well. The comparison to theoretical calculations provides crucial information on dynamic of the created system especially at the freeze-out conditions, which are poorly known from previous flow measurements.