Measurement of two- and four-particle correlations in pPb and PbPb collisions at CMS

Results of two- and four-particle angular two-dimensional correlations in pPb collisions at a nucleon-nucleon center-of-mass energy of 5.02~TeV, collected with the CMS detector, are presented. In high-multiplicity pPb events a ridge-like structure at the near-side emerges in two-particle $\Delta\eta - \Delta\phi$ correlation. It is compared to the ridge found in 2.76~TeV PbPb collisions. In both systems, the ridge yield rises, reach a maximum at $p_{T}\approx$1-3~GeV/c and then decreases at higher $p_{T}$, and increases monotonically with multiplicity. The 2-nd order Fourier harmonic has qualitatively similar $p_{T}$ dependence, but with a moderate multiplicity dependence in both systems. The multiplicity dependence of the 3-rd Fourier harmonic is rather similar for pPb and PbPb collisions. Color glass condensate and hydrodynamic predictions are compared to the experimental results.