Measurement of higher-order harmonic azimuthal anisotropy in PbPb collisions at s NN =2.76 TeV

Abstract

Measurements are presented by the CMS Collaboration at the Large Hadron Collider (LHC) of the higher-order harmonic coefficients that describe the azimuthal anisotropy of charged particles emitted in sNN=2.76 TeV PbPb collisions. Expressed in terms of the Fourier components of the azimuthal distribution, the n=3-6 harmonic coefficients are presented for charged particles as a function of their transverse momentum (0.3 < pT < 8.0GeV/c), collision centrality (0%-70%), and pseudorapidity (|η| < 2.0). The data are analyzed using the event plane, multiparticle cumulant, and Lee-Yang zeros methods, which provide different sensitivities to initial-state fluctuations. Taken together with earlier LHC measurements of elliptic flow (n=2), the results on higher-order harmonic coefficients develop a more complete picture of the collective motion in high-energy heavy-ion collisions and shed light on the properties of the produced medium. © 2014 CERN, for the CMS Collaboration.