MEASUREMENT OF TWO- AND FOUR-PARTICLE CORRELATIONS IN P-PB AND PB-PB COLLISIONS AT CMS

Abstract

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 fi correlation. It is compared to the ridge found in 2.76 TeV PbPb collisions. In both systems, the ridge yield rises, reaches a maximum at approx. 1-3 GeV/c and then decreases at higher pt, and increases monotonically with multiplicity. The 2-nd order Fourier harmonic has qualitatively similar p_Т 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.