Correlations and fluctuations measured by the CMS experiment in pp and PbPb

Understand

Measurements of charged dihadron angular correlations are presented in proton-proton (pp) and Lead-Lead (PbPb) collisions, over a broad range of pseudorapidity and azimuthal angle, using the CMS detector at the LHC.

• In very high multiplicity pp events at center-of-mass energy of 7 TeV, a striking &#34;ridge&#34;-like structure emerges in the two-dimensional correlation function for particle pairs with intermediate pt of 1-3 GeVc, in the kinematic region 2.0<|\Delta\eta|<4.8 and small \Delta\phi, which is similar to observations in heavy-ion collisions.
• Studies of this new effect as a function of particle transverse momentum are discussed.
• The long-range and short-range dihadron correlations are also studied in PbPb collision at a nucleon-nucleon center-of-mass energy of 2.76 TeV, as a function of transverse momentum and collision centrality.