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

You Zhou

doi:10.1016/j.nuclphysa.2017.04.016

Abstract

The second and the third order anisotropic flow, V2 and V3, 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 (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 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.

Highlights

The primary goal of the ultra-relativistic heavy-ion collisions program is to create and study the quarkgluon plasma (QGP), a state of matter whose existence under extreme conditions is predicted by quantum chromodynamics
The χmn is a newly proposed observable called the non-linear mode coefficient which quantifies the contributions of non-linear model without contribution from v2 and/or v3 [13]. We investigate both the linear and non-linear contributions to higher order anisotropic flow, with above mentioned observables
It is observed that v4L has a dominant contribution to v4{2} for the centrality range 0-30% and it only changes modestly from central to peripheral collisions

Summary

Introduction

The primary goal of the ultra-relativistic heavy-ion collisions program is to create and study the quarkgluon plasma (QGP), a state of matter whose existence under extreme conditions is predicted by quantum chromodynamics. The anisotropic flow Vn, defined as Vn = vneinΨn , have been measured at the CERN Large Hadron Collider (LHC) [2, 3] These measurements of n coefficients, combine with the hydrodynamic model calculations, provide compelling evidence that the created QGP matter appears to behave like an almost perfect fluid. VnNL and VnL represent the non-linear and linear contributions to the higher order anisotropic flow, whose magnitudes are denoted as vn,ml (or vn,mlk) and vLn , respectively. The χmn (or χmnl) is a newly proposed observable called the non-linear mode coefficient which quantifies the contributions of non-linear model without contribution from v2 and/or v3 [13] In these proceedings, we investigate both the linear and non-linear contributions to higher order anisotropic flow, with above mentioned observables

Analysis Details

Results and Discussions

Summary