Charged hadron azimuthal anisotropy ($v_{2}$) in $\sqrt{s_{NN}} = 2.76$ TeV PbPb collisions from CMS

During the past decade, azimuthal correlation measurements have played a pivotal role in our understanding of the properties of high density QCD matter through their sensitivity to the early stage evolution of relativistic heavy-ion collisions. The CMS experiment has measured the anisotropy parameter, $v_{2}$, using four different methods: event-plane, two and four particle cumulants, and Lee-Yang Zeros. Consistent results are found for the different methods after considering their respective sensitivities to non-flow correlations and event-by-event fluctuations in the initial conditions. The anisotropy is studied as a function of transverse momentum, pseudorapidity and centrality in a broad kinematic range: $0.3 < p_{T} < 12 $ GeV/$c$, $\mid\eta\mid< 2.4$, and in 12 centrality classes in the range 0-80\%.