Overview of results on flow and correlations from the CMS collaboration

Highlights of the results obtained by the CMS experiment at the LHC on collective flow and dihadron correlations in PbPb collisions are presented. At lower transverse momenta of the outgoing particles and for a wide range of collision centralities, the $2^{nd}$- through $6^{th}$-order Fourier components of the azimuthal distribution have been found using different analysis techniques with different sensitivities to non-flow and flow fluctuation effects. An ultra-central collision trigger allows the Fourier components to be extended to a region of centrality where initial-state effects are expected to be small. A high-$p_{T}$ single-track trigger has allowed the elliptic anisotropy ($v_{2}$) and higher-order harmonics to be explored up to $\approx 60~{\rm GeV/c}$, as a function of pseudorapidity and collision centrality. The CMS results provide new information on both the hydrodynamic properties of the medium at low $p_{T}$ and the path-length dependence of in-medium parton energy loss at high $p_{T}$. By subtracting the long-range in pseudorapidity anisotropy components arising from hydrodynamic flow from dihadron correlation results it is possible to gain further insight into the medium effect on dijets. This is done with a study of the ``near-side" and ``away-side" yields of dijets measured in PbPb collisions compared to those found in pp collisions.