Mixed higher-order flow harmonics and nonlinear response coefficients in PbPb collisions at 2.76 and 5.02 TeV with CMS

Shengquan Tuo

doi:10.1016/j.nuclphysa.2017.05.064

Abstract

The mixed higher-order flow harmonics and nonlinear response coefficients of charged particles are presented as a function of pT and centrality in PbPb collisions at sNN=2.76 TeV and 5.02 TeV with the CMS detector. The results are obtained using the scalar product method, and cover a pT range from 0.3 GeV/c to 8.0 GeV/c, pseudorapidity |η|<2.4, and a centrality range of 0-60%. The mixed harmonic results at 5.02 TeV are compared to the matching higher-order flow harmonics from two-particle correlations, which measure vn values with respect to the n-th order event plane. It is observed that the nonlinear response coefficients of the odd harmonics are larger than the even harmonics ones. The results are compared with hydrodynamic predictions using different shear viscosity to entropy density ratios and different initial conditions.

Highlights

Anisotropic flow plays a major role in probing the properties of the produced medium at the Relativistic Heavy Ion Collider (RHIC) at BNL and Large Hadron Collider (LHC) at CERN
The mixed higher-order flow h√armonics and nonlinear response coefficients of charged particles have been studied in PbPb collisions at sNN = 2.76 TeV and 5.02 TeV using the CMS detector
The measurements are done with the scalar product method, covering a pT range from 0.3 GeV/c to 8.0 GeV/c, |η| < 2.4 and centrality range of 0-60%

Summary

Introduction

Anisotropic flow plays a major role in probing the properties of the produced medium at the Relativistic Heavy Ion Collider (RHIC) at BNL and Large Hadron Collider (LHC) at CERN. V4 and higher harmonics can arise from initial state anisotropies in the same order harmonic (linear response) or can be induced by lower-order harmonics (nonlinear response) [6, 9, 10]. Recent hydrodynamic studies show that the nonlinear response coefficients probe the apnrodpTaehbrtioiseusat n3oa0flytmhseiislsliiyossntpeePmrbfPoatrbmfmreedienziuems-iounumgt -aabnbidaosuatreev1e0wn0etsemkailtlyli√soensnNsPNibti=Pveb2t.mo76itnhTiemeiVun.mitTi-ahbleidaesscneasvliateyrntpflsruoacdttuu√acttsiomNnNest=h[6o5,d.90u]2.seTdeiVn the analysis always measures the root-mean-square of vn distribution. This analysis presents the mixed higher-order flow harmonics, v4 with respect to Ψ2 (v4{Ψ22}), v5 with respect to Ψ2 and Ψ3 (v5{Ψ23}), v6 with respect to Ψ2 (v6{Ψ222}), v6 with respect to Ψ3 (v6{Ψ33}) and v7 with respect to Ψ2 and Ψ3 (v7{Ψ223}). More details about the CMS detector and this analysis can be found in [11, 12]

Results for mixed harmonics

Results for nonlinear response coefficients

Summary