Studies of azimuthal dihadron correlations in ultra-central PbPb collisions at √sNN = 2.76 TeV

S. Chatrchyan, V. Khachatryan, A. M. Sirunyan, A. Tumasyan, W. Adam, T. Bergauer, M. Dragicevic, J. Erö, C. Fabjan, M. Friedl, R. Frühwirth, V. M. Ghete, C. Hartl, N. Hörmann, J. Hrubec, M. Jeitler, W. Kiesenhofer, V. Knünz, M. Krammer, I. KrätschmerD. Liko, I. Mikulec, D. Rabady, B. Rahbaran, H. Rohringer, R. Schöfbeck, J. Strauss, A. Taurok, W. Treberer-Treberspurg, W. Waltenberger, C. E. Wulz, V. Mossolov, N. Shumeiko, J. Suarez Gonzalez, S. AlDerweireldt, M. Bansal, S. Bansal, T. Cornelis, E. A. DeWolf, X. Janssen, A. Knutsson, S. Luyckx, L. Mucibello, S. Ochesanu, B. Roland, R. Rougny, H. Van Haevermaet, P. Van Mechelen, N. Van Remortel, A. Van Spilbeeck

Research output: Contribution to journalArticlepeer-review

65 Scopus citations

Abstract

Azimuthal dihadron correlations of charged particles have been measured in PbPb collisions at √sNN = 2.76TeV by the CMS collaboration, using data from the 2011 LHC heavy-ion run. The data set incluDes a sample of ultra-central (0-0.2% centrality) PbPb events collected using a trigger based on total transverse energy in the hadron forward calorimeters and the total multiplicity of pixel clusters in the silicon pixel tracker. A total of about 1.8 million ultra-central events were recorDed, corresponding to an integrated luminosity of 120 μb-1. The observed correlations in ultra-central PbPb events are expected to be particularly sensitive to initial-state fluctuations. The single-particle anisotropy Fourier harmonics, from v2 to v6, are extracted as a function of particle transverse momentum. At higher transverse momentum, the v2 harmonic becomes significantly smaller than the higher-orDer vn (n ≥ 3). The pT-averaged v2 and v3 are found to be equal within 2%, while higher-orDer vn Decrease as n increases. The breakdown of factorization of dihadron correlations into single-particle azimuthal anisotropies is observed. This effect is found to be most prominent in the ultra-central PbPb collisions, where the initial-state fluctuations play a dominant role. A comparison of the factorization data to hydrodynamic predictions with event-by-event fluctuating initial conditions is also presented.

Original languageEnglish (US)
Article number88
JournalJournal of High Energy Physics
Volume2014
Issue number2
DOIs
StatePublished - Feb 2014

Keywords

  • Harmonic flow
  • Heavy Ions
  • Relativistic heavy ion physics

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

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