Flow Phenomena at CMS

Azimuthal angle correlation measurements of charged hadrons are presented in pPb collisions at $\sqrt{s_{NN}} = 5.02$ TeV and PbPb collisions at $\sqrt{s_{NN}} = 2.76$ TeV. The second- ($v_2$) and third-order ($v_3$) Fourier harmonics are extracted using two-particle correlation and four-particle cumulant methods covering similar multiplicity ranges in pPb and PbPb over a wide range of pseudorapidity. A large four-particle $v_2$ as a function of multiplicity in pPb collisions is comparable to the PbPb system . Nearly identical two-particle correlation $v_3$ signals between the pPb and PbPb systems are observed. In ultra-central PbPb collisions, factorization of the Fourier harmonics is shown. The observed factorization breakdown is found to be consistent with the $p_T$ dependent event-by-event fluctuating event-plane angle in the hydrodynamic picture.