Journal of High Energy Physics
First measurements of dihadron correlations for charged particles are presented for central PbPb collisions at a nucleon-nucleon center-of-mass energy of 2.76 TeV over a broad range in relative pseudorapidity (∆η) and the full range of relative azimuthal angle (∆η). The data were collected with the CMS detector, at the LHC. A broadening of the away-side (∆ϕ ≈ π) azimuthal correlation is observed at all ∆η, as compared to the measurements in pp collisions. Furthermore, long-range dihadron correlations in ∆η are observed for particles with similar ϕ values. This phenomenon, also known as the “ridge”, persists up to at least |∆η| = 4. For particles with transverse momenta (pT) o f2-4 GeV/c, the ridge is found to be most prominent when these particles are correlated with particles of pT = 2-6 GeV/c, and to be much reduced when paired with particles of pT = 10-12 GeV/c.
Chatrchyan, S.; Baarmand, Marc M.; Dorney, B.; Guragain, Samir; Hohlmann, Marcus; Kalakhety, Himali; Ralich, Robert; Vodopiyanov, Igor; and The CMS Collaboration, "Long-range And Short-range Dihadron Angular Correlations In Central PbPb Collisions At psNN = 2:76 TeV" (2011). Aerospace, Physics, and Space Science Faculty Publications. 565.