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Measurement of the azimuthal anisotropy for charged particle production in sqrt(s_NN) = 2.76 TeV lead-lead collisions with the ATLAS detector

G. Aad L. Aperio Bella 1 B. Aubert 1 N. Berger 1 J. Colas 1 M. Delmastro 1 L. Di Ciaccio 1 T.K.O. Doan 1 S. Elles 1 C. Goy 1 L. Helary 1 T. Hryn'Ova 1 A. Jérémie 1 S. Jézéquel 1 M. Kataoka 1 J. Labbe 1 R. Lafaye 1 J. Leveque 1 V.P. Lombardo 1 N. Massol 1 P. Perrodo 1 E. Petit 1 H. Przysiezniak 1 G. Sauvage 1 E. Sauvan 1 M. Schwoerer 1 T. Todorov 1 D. Tsionou 1 I. Wingerter-Seez 1 R. Zitoun 1 Y. Zolnierowski 1 C. Biscarat 2 E. Cogneras 2 G. Rahal 2 S. Abdel Khalek 3 H. Abreu 3 N. Andari 3 C. Arnault 3 E. Augé 3 P. Barrillon 3 M. Benoit 3 S. Binet 3 C. Bourdarios 3 C. de la Taille 3 J.B. de Vivie de Regie 3 L. Duflot 3 M. Escalier 3 L. Fayard 3 D. Fournier 3 J.-F. Grivaz 3 S. Henrot-Versillé 3 J. Hrivnac 3 L. Iconomidou-Fayard 3 J. Idarraga 3 M. Kado 3 N. Lorenzo Martinez 3 A. Lounis 3 N. Makovec 3 P. Matricon 3 F. Niedercorn 3 L. Poggioli 3 P. Puzo 3 A. Renaud 3 D. Rousseau 3 G. Rybkin 3 J.B. Sauvan 3 J. Schaarschmidt 3 A.C. Schaffer 3 E. Scifo 3 L. Serin 3 S. Simion 3 R. Tanaka 3 M. Teinturier 3 J.J. Veillet 3 I. Vukotic 3 F. Wicek 3 D. Zerwas 3 Z. Zhang 3 D. Boumediene 4 Emmanuel Busato 4 D. Calvet 4 S. Calvet 4 Reina Coromoto Camacho Toro 4 Diane Cinca 5 J. Donini 4 R. Febbraro 4 N. Ghodbane 4 C. Guicheney 4 H. Liao 4 D. Pallin 4 Daniela Paredes Hernández 4 F. Podlyski 4 C. Santoni 4 L. P. Says 4 F. Vazeille 4 S. Albrand 6 M.L. Andrieux 6 Q. Buat 6 B. Clement 6 J. Collot 6 S. Crépé-Renaudin 6 B. Dechenaux 6 T. Delemontex 6 P.A. Delsart 6 M.H. Genest 6 J.Y. Hostachy 6 E. Laisne 6 F. Ledroit-Guillon 6 A. Lleres 6 A. Lucotte 6 F. Malek 6 P. Martin 6 F. Polci 6 J. Stark 6 X. Sun 6 B. Trocmé 6 J. Wang 6 C. Weydert 6 S. Aoun 7 C. P. Bee 7 C. Bertella 7 N. Bousson 7 J. C. Clémens 7 Y. Coadou 7 F. Djama 7 F. Etienne 7 L. Feligioni 7 F. Henry-Couannier 7 D. Hoffmann 7 F. Hubaut 7 E. B. F. G. Knoops 7 E. Le Guirriec 7 B. Li 7 J. Maurer 7 E. Monnier 7 J. Odier 7 P. Pralavorio 7 Z. Qian 7 A. Rozanov 7 M. Talby 7 N. Tannoury 7 S. Tisserant 7 J. Toth 7 F. Touchard 7 L. Vacavant 7
Abstract : Differential measurements of charged particle azimuthal anisotropy are presented for lead-lead collisions at sqrt(s_NN) = 2.76 TeV with the ATLAS detector at the LHC, based on an integrated luminosity of approximately 8 mb^-1. This anisotropy is characterized via a Fourier expansion of the distribution of charged particles in azimuthal angle (phi), with the coefficients v_n denoting the magnitude of the anisotropy. Significant v_2-v_6 values are obtained as a function of transverse momentum (0.5=3 are found to vary weakly with both eta and centrality, and their pT dependencies are found to follow an approximate scaling relation, v_n^{1/n}(pT) \propto v_2^{1/2}(pT). A Fourier analysis of the charged particle pair distribution in relative azimuthal angle (Dphi=phi_a-phi_b) is performed to extract the coefficients v_{n,n}=. For pairs of charged particles with a large pseudorapidity gap (|Deta=eta_a-eta_b|>2) and one particle with pT<3 GeV, the v_{2,2}-v_{6,6} values are found to factorize as v_{n,n}(pT^a,pT^b) ~ v_n(pT^a)v_n(pT^b) in central and mid-central events. Such factorization suggests that these values of v_{2,2}-v_{6,6} are primarily due to the response of the created matter to the fluctuations in the geometry of the initial state. A detailed study shows that the v_{1,1}(pT^a,pT^b) data are consistent with the combined contributions from a rapidity-even v_1 and global momentum conservation. A two-component fit is used to extract the v_1 contribution. The extracted v_1 is observed to cross zero at pT\sim1.0 GeV, reaches a maximum at 4-5 GeV with a value comparable to that for v_3, and decreases at higher pT.
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Submitted on : Friday, March 16, 2012 - 11:50:27 AM
Last modification on : Thursday, June 17, 2021 - 3:47:35 AM

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G. Aad, L. Aperio Bella, B. Aubert, N. Berger, J. Colas, et al.. Measurement of the azimuthal anisotropy for charged particle production in sqrt(s_NN) = 2.76 TeV lead-lead collisions with the ATLAS detector. Physical Review C, American Physical Society, 2012, 86, pp.014907. ⟨10.1103/PhysRevC.86.014907⟩. ⟨in2p3-00679743⟩

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