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Centrality dependence of dihadron correlations and azimuthal anisotropy harmonics in PbPb collisions at √SNN = 2.76 Tev

  • Author(s): Chatrchyan, S
  • Khachatryan, V
  • Sirunyan, AM
  • Tumasyan, A
  • Adam, W
  • Bergauer, T
  • Dragicevic, M
  • Erö, J
  • Fabjan, C
  • Friedl, M
  • Frühwirth, R
  • Ghete, VM
  • Hammer, J
  • Hoch, M
  • Hörmann, N
  • Hrubec, J
  • Jeitler, M
  • Kiesenhofer, W
  • Knapitsch, A
  • Krammer, M
  • Liko, D
  • Mikulec, I
  • Pernicka, M
  • Rahbaran, B
  • Rohringer, C
  • Rohringer, H
  • Schöfbeck, R
  • Strauss, J
  • Taurok, A
  • Teischinger, F
  • Wagner, P
  • Waltenberger, W
  • Walzel, G
  • Widl, E
  • Wulz, CE
  • Mossolov, V
  • Shumeiko, N
  • Suarez Gonzalez, J
  • Bansal, S
  • Benucci, L
  • Cornelis, T
  • de Wolf, EA
  • Janssen, X
  • Luyckx, S
  • Maes, T
  • Mucibello, L
  • Ochesanu, S
  • Roland, B
  • Rougny, R
  • Selvaggi, M
  • et al.
Abstract

Measurements from the CMS experiment at the LHC of dihadron correlations for charged particles produced in PbPb collisions at a nucleon-nucleon centre-of-mass energy of 2. 76 TeV are presented. The results are reported as a function of the particle transverse momenta (pT) and collision centrality over a broad range in relative pseudorapidity (Δη) and the full range of relative azimuthal angle (Δφ). The observed two-dimensional correlation structure in Δη and Δφ is characterised by a narrow peak at (Δη,Δφ)≈(0,0) from jet-like correlations and a long-range structure that persists up to at least {pipe}Δη{pipe}=4. An enhancement of the magnitude of the short-range jet peak is observed with increasing centrality, especially for particles of pT around 1-2 GeV/c. The long-range azimuthal dihadron correlations are extensively studied using a Fourier decomposition analysis. The extracted Fourier coefficients are found to factorise into a product of single-particle azimuthal anisotropies up to pT≈3-3. 5 GeV/c for at least one particle from each pair, except for the second-order harmonics in the most central PbPb events. Various orders of the single-particle azimuthal anisotropy harmonics are extracted for associated particle pT of 1-3 GeV/c, as a function of the trigger particle pT up to 20 GeV/c and over the full centrality range. © 2012 CERN for the benefit of the CMS collaboration.

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