Measurement of the Azimuthal Anisotropy for Charged Particle Production in √{S_{NN}} = 2.76 TeV Lead-Lead Collisions with the ATLAS Detector

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Measurement of the Azimuthal Anisotropy for Charged Particle Production in √{S_{NN}} = 2.76 TeV Lead-Lead Collisions with the ATLAS Detector

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title Measurement of the Azimuthal Anisotropy for Charged Particle Production in √{S_{NN}} = 2.76 TeV Lead-Lead Collisions with the ATLAS Detector
contributor.author Aad, G.
contributor.author Abbott, B.
contributor.author Abdallah, J.
contributor.author Abdel Khalek, S.
contributor.author Abdelalim, A. A.
contributor.author Abdesselam, A.
contributor.author Abdinov, O.
contributor.author Ahsan, Mahsana
contributor.author Izen, Joseph M.
contributor.author Lou, Xinchou
contributor.author Reeves, Kendall
contributor.utdAuthor Lou, Xinchou
contributor.utdAuthor Izen, Joseph M.
contributor.VIAF 250674117 (Izen, JM)
contributor.VIAF 250674117 (Izen, JM)
contributor.ORCID 0000-0003-0867-2189 (Lou, X)
description.abstract Differential measurements of charged particle azimuthal anisotropy are presented for lead-lead collisions at √{S_{NN}} = 2.76 TeV with the ATLAS detector at the LHC, based on an integrated luminosity of approximately 8 μb⁻¹. This anisotropy is characterized via a Fourier expansion of the distribution of charged particles in azimuthal angle relative to the reaction plane, with the coefficients vn denoting the magnitude of the anisotropy. Significant v₂–v₆ values are obtained as a function of transverse momentum (0.5 < p_T < 20 GeV), pseudorapidity (|η| < 2.5), and centrality using an event plane method. The ν_n values for n ≥ 3 are found to vary weakly with both η and centrality, and their p_T dependencies are found to follow an approximate scaling relation, v_{1/n / n} (p_T) ∝ v{1/2 / 2} (p_T), except in the top 5% most central collisions. A Fourier analysis of the charged particle pair distribution in relative azimuthal angle (Δφ = φ_a − φ_b) is performed to extract the coefficients v_{n,n} = (cos nΔφ). For pairs of charged particles with a large pseudorapidity gap (|Δη = η_a−η_b| > 2) and one particle with pT < 3 GeV, the v₂,₂ – v₆,₆ values are found to factorize as v_{n,n}(p_T^a, pp_T^b) ≈ v_n(p_T^a) ν_n (p_T^b) in central and midcentral events. Such factorization suggests that these values of v₂,₂ – v₆,₆ are primarily attributable to the response of the created matter to the fluctuations in the geometry of the initial state. A detailed study shows that the v₁,₁ (p_T^a,p_T^b) data are consistent with the combined contributions from a rapidity-even v₁ and global momentum conservation. A two-component fit is used to extract the v₁ contribution. The extracted v₁ is observed to cross zero at p_T ≈ 1.0 GeV, reaches a maximum at 4–5 GeV with a value comparable to that for v₃, and decreases at higher p_T.
identifier.issn 0556-2813
identifier.uri http://hdl.handle.net/10735.1/4268
identifier.bibliographicCitation Aad, G., B. Abbott, J. Abdallah, S. Abdel Khalek, et al. 2014. "Measurement of the azimuthal anisotropy for charged particle production in √{S_{NN}} = 2.76 TeV lead-lead collisions with the ATLAS detector." Physical Review C - Nuclear Physics 86(1), doi:10.1103/PhysRevC.86.014907
identifier.volume 86
identifier.issue 1
subject Azimuthal anisotropy
subject Lead-lead interactions
subject Fourier series
date.created 2012-07-24
date.issued 2012-07-24
publisher American Physical Society
relation.uri http://dx.doi.org/10.1103/PhysRevC.86.014907
rights CC BY 3.0 (Attribution)
rights ©2014 CERN for the ATLAS collaboration
rights.uri http://creativecommons.org/licenses/by/3.0/
language.iso en_US
source Physical Review C - Nuclear Physics

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CC BY 3.0 (Attribution) Except where otherwise noted, this item's license is described as CC BY 3.0 (Attribution)