Studies of azimuthal dihadron correlations in ultra-central PbPb collisions at √sNN=2.76 TeV
Buchmann, Marco A.
Marini, Andrea C.
Martinez Ruiz del Arbol, Pablo
Ronga, Frédéric J.
Weber, Hannsjörg A.
- Journal Article
Rights / licenseCreative Commons Attribution 4.0 International
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 v 2 to v 6, are extracted as a function of particle transverse momentum. At higher transverse momentum, the v 2 harmonic becomes significantly smaller than the higher-order v n (n ≥ 3). The p T-averaged v 2 and v 3 are found to be equal within 2%, while higher-order v n 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 Show more
Journal / seriesJournal of High Energy Physics
Pages / Article No.
SubjectRelativistic heavy ion physics; Heavy Ions; Harmonic flow
Organisational unit03381 - Pauss, Felicitas (emeritus)
03593 - Dissertori, Günther
03904 - Wallny, Rainer
08803 - Grab, Christoph (Tit.Prof.)
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