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

The second and the third order anisotropic flow, V 2 and V 3 , are determined 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 ( V 4 , V 5 and V 6 ) in Pb–Pb collisions at sNN=2.76 TeV using the ALICE detector at the Large Hadron Collider (LHC). A significant contribution from a non-linear 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.