Measurement of the azimuthal anisotropy for charged particle production in √sNN=2.76 TeV lead-lead collisions with the ATLAS detector
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American Physical Society
Aad, G., Abbott, B., Abdallah, J., Khalek, S. A., Abdelalim, A. A., Abdesselam, A., ... & Abreu, H. (2012). Measurement of the azimuthal anisotropy for charged particle production in s N N= 2.76 TeV lead-lead collisions with the ATLAS detector. Physical Review C, 86(1), 014907. [https://doi.org/10.1103/PhysRevC.86.014907]
SponsorshipANPCyT ; YerPhI, Armenia; Australian Research Council; BMWF, Austria; Azerbaijan National Academy of Sciences (ANAS); SSTC, Belarus; National Council for Scientific and Technological Development (CNPq); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP); Natural Sciences and Engineering Research Council of Canada; NRC, Canada; Canada Foundation for Innovation; CERN; Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT); Chinese Academy of Sciences; Ministry of Science and Technology, China; National Natural Science Foundation of China; Departamento Administrativo de Ciencia, Tecnologia e Innovacion Colciencias; Ministry of Education, Youth & Sports - Czech Republic Czech Republic Government; DNRF, Denmark; Danish Natural Science Research Council; Lundbeckfonden; European Union (EU); Centre National de la Recherche Scientifique (CNRS); CEA-DSM/IRFU, France; GNAS, Georgia; Federal Ministry of Education & Research (BMBF); German Research Foundation (DFG); HGF, Germany; Max Planck Society; Alexander von Humboldt Foundation; Greek Ministry of Development-GSRT; Israel Science Foundation; MINERVA, Israel; German-Israeli Foundation for Scientific Research and Development; DIP, Israel; Benoziyo Center, Israel; Istituto Nazionale di Fisica Nucleare (INFN); Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) Japan Society for the Promotion of Science; CNRST, Morocco; FOM (The Netherlands) Netherlands Government; Netherlands Organization for Scientific Research (NWO) Netherlands Government; RCN, Norway; Ministry of Science and Higher Education, Poland; GRICES, Portugal; Portuguese Foundation for Science and Technology; MERYS (MECTS), Romania; MES of Russia; Russian Federation; JINR; MSTD, Serbia; MSSR, Slovakia; Slovenian Research Agency - Slovenia; MVZT, Slovenia; DST/NRF, South Africa; Spanish Government; SRC, Sweden; Wallenberg Foundation, Sweden; SER, Switzerland; Swiss National Science Foundation (SNSF); Cantons of Bern and Geneva, Switzerland; National Science Council of Taiwan; Ministry of Energy & Natural Resources - Turkey; Royal Society of London; Leverhulme Trust; United States Department of Energy (DOE); National Science Foundation (NSF); ICREA; Science & Technology Facilities Council (STFC) ST/L001144/1 ST/K001248/1 ST/K001361/1 ST/K001310/1 ATLAS Upgrades ST/H00100X/2 GRIDPP ST/K001310/1 ST/K001361/1 ATLAS Upgrades ST/K001310/1 LHCb PP/E003087/1 ST/K001418/1 ST/J005460/1 ST/I005803/1 GRIDPP ST/H00100X/1 ST/J004944/1 ST/K001337/1 ATLAS ST/I005811/1 ST/H001093/2 ST/H001026/2 ST/I006080/1 ST/H001069/2 ST/K001337/1 ST/K001361/1 ATLAS ST/K501840/1 GRIDPP PP/E003699/1 ST/H001042/1 ST/K000705/1 ST/I003517/1 ST/I005803/1 ST/K001329/1 ATLAS ST/L000970/1 ATLAS Upgrade ST/L001195/1 ST/L000970/1 ST/J002798/1 ST/M001431/1 ST/K001361/1 LHCb Upgrades ST/K001310/1 LHCb Upgrades ST/F007337/1 PP/E003699/2 ST/I003525/1 ST/H001042/2 PP/E000355/1 ST/K00073X/1 ST/G502320/1 ST/H001026/1 ST/I003142/1 ST/K001361/1 LHCb ST/K001264/1 ATLAS ST/K001310/1 ATLAS ST/H001093/1 ST/K501840/1 ST/M001474/1 PP/E000347/1 ST/J004928/1 ATLAS Upgrade ST/I000186/1 ST/L001004/1 ST/K003658/1 ST/K001248/1 ATLAS ST/J005576/1 ST/K003658/1 GRIDPP ST/K001361/1 MINOS/MINOS+ ST/J004928/1 PP/E002757/1 ATLAS
Differential measurements of charged particle azimuthal anisotropy are presented for lead-lead collisions at √sNN=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<pT<20 GeV), pseudorapidity (|η|<2.5), and centrality using an event plane method. The vn values for n≥3 are found to vary weakly with both η and centrality, and their pT dependencies are found to follow an approximate scaling relation, v1/nn(pT)∝v1/22(pT), except in the top 5% most central collisions. A Fourier analysis of the charged particle pair distribution in relative azimuthal angle (Δφ=φa−φb) is performed to extract the coefficients vn,n=⟨cosnΔφ⟩. For pairs of charged particles with a large pseudorapidity gap (|Δη=ηa−ηb|>2) and one particle with pT<3 GeV, the v2,2–v6,6 values are found to factorize as vn,n(paT,pbT)≈vn(paT)vn(pbT) 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(paT,pbT) 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 pT≈1.0 GeV, reaches a maximum at 4–5 GeV with a value comparable to that for v3, and decreases at higher pT.