Title
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Studies of azimuthal dihadron correlations in ultra-central PbPb collisions at = 2.76 TeV
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Author
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Institution/Organisation
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CMS Collaboration
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Abstract
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Azimuthal dihadron correlations of charged particles have been measured in PbPb collisions at = 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 mu b -aEuro parts per thousand 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 a parts per thousand yenaEuro parts per thousand 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. |
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Language
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English
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Source (journal)
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Journal of high energy physics. - Bristol
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Publication
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Bristol
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2014
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ISSN
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1126-6708
1029-8479
[online]
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DOI
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10.1007/JHEP02(2014)088
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Volume/pages
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2
(2014)
, p. 1-38
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Article Reference
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088
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ISI
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000331974800001
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Medium
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E-only publicatie
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Full text (Publisher's DOI)
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Full text (open access)
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