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

摘要

The second and the third order anisotropic flow, V-2 and V-3, are determined by the corresponding initial spatial anisotropy coefficients, epsilon(2) and epsilon(3), in the initial density distribution. On the contrary, the higher order anisotropic flow V-n (n > 3), in addition to their dependence on the same order initial anisotropy coefficient epsilon(n), 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 root S-NN = 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.