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Rapidity Dependence of Pion Elliptic Flow

Rapidity Dependence of Pion Elliptic Flow. Hironori Ito 1 Erik Johnson 2 Steve Sanders 2. 1 Brookhaven National Laboratory 2 University of Kansas. BRAHMS Collaboration. BRAHMS Collaboration. I.Arsene, I.G. Bearden 7 , D. Beavis 1 , S.Bekele 11 , C. Besliu 10 , B. Budick 6 ,

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Rapidity Dependence of Pion Elliptic Flow

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  1. Rapidity Dependence of Pion Elliptic Flow Hironori Ito1 Erik Johnson2 Steve Sanders2 1Brookhaven National Laboratory 2University of Kansas BRAHMS Collaboration

  2. BRAHMS Collaboration I.Arsene, I.G. Bearden7, D. Beavis1, S.Bekele11, C. Besliu10, B. Budick6, H. Bøggild7, C. Chasman1, C. H. Christensen7, P. Christiansen7, R.Clarke10, R. Debbe1,J. J. Gaardhøje, K. Hagel8, H. Ito1, A. Jipa10, J. I. Jordre10, F. Jundt2, E.B.Johnson11, J.I.Jordre9, C.Jørgensen7, R. Karabowicz3, E. J. Kim11, T.M. Larsen7, J. H. Lee1, Y. K.Lee5, S.Lindal12, G. Løvhøjden2, Z. Majka3, M. Murray11, J. Natowitz8, B.S.Nielsen7, D.Ouerdane7, R.Planeta4, F. Rami2, C.Ristea7, O.Ristea10, D. Röhrich9, B. H. Samset12, S. J. Sanders11, R.A.Sheetz1, P. Staszel3, T.S. Tveter12, F.Videbæk1, R. Wada8, H.Yang9, Z. Yin9,and I. S. Zgura10 1Brookhaven National Laboratory, USA, 2IReS and Université Louis Pasteur, Strasbourg, France 3Jagiellonian University, Cracow, Poland, 4Institute of Nuclear Physics, Cracow, Poland, 5Johns Hopkins University, Baltimore, USA, 6New York University, USA, 7Niels Bohr Institute, University of Copenhagen, Denmark, 8Texas A&M University, College Station. USA, 9University of Bergen, Norway, 10University of Bucharest, Romania, 11University of Kansas, Lawrence,USA,12 University of Oslo Norway

  3. PID detectors Event plane detectors BRAHMS Detector Setup

  4. Event Plane Detectors • Flow Ring 2 (silicon strips): • 42 segments per 2π • -2 < η < 0.2 • Flow Ring 3 (silicon strips): • 42 segments per 2π • -2 < η < 1.2 • Si Ring 1 (silicon strips): • 6 segments per 2π • -2.4 < η < 0.8 • Tile Ring 1 (scintillator tile): • 6 segments per 2π • -2 < η < -0.8 Flow Ring 3 Si Ring 1 Flow Ring 2 Tile Ring 1

  5. φ Introduction to Flow ...final momentum anisotropy Initial spatial anisotropy... ...after rescattering leads to ... Elliptic Flow: n = 2

  6. PHOBOS and STAR have measured pT integrated v2 over a wide pseudorapidity range. →pT integrated v2 has strong pseudorapidity dependence. Charged Hadron STAR also measured charged hadron v2(pT) at forward rapidity, and find a large pT dependence. Rapidity Dependence?Current Status

  7. Method Nth order event plane Methods describe by A. M. Poskanzer and S. A. Voloshin Phys. Rev. C58 (1998) 1671 Event plane resolution correction Observed v2 Real v2 a,b and c are the Scintillator Tile, the Silicon Strip and the Beam-Beam counters

  8. Particle Identification at Midrapidity • Time-of-Flight Identification • Pions: 2.5 GeV/c • Protons: 4 GeV/c • Kaons: 2 GeV/c

  9. Particle Identification at Forward Rapidity • RICH identification • Pions:28 GeV/c • Protons: 35 GeV/c • Kaons: 28 GeV/c

  10. 10-20% Central 10-20% Central Charged Hadron Errors are statistical only Errors are statistical only Charged Hadron V2 at Midrapidity Strong pT dependence is seen at midrapidity.

  11. 10-20% central events ...pion v2(pT) is also consistent with STAR data. 10-20% central events Errors are statistical only Error is statistical only Pion V2 at Midrapidity

  12. η = 0 η = 3.2 Pions Error is statistical only Pion Errors are statistical only Pion elliptic flow at forward rapidity is very smilar to that at midrapidity. Pion V2 at Forward Rapidity η = 3.2 10-20% Find strong pt dependence Pion Error is statistical only

  13. η= 0 3D Hydrodynamic calculation also shows a very small pseudorapidity dependence. η= 1 3D Hydro (Hirano) η= 3.2 Rapidity Dependence Small η dependence found. Charged hadrons η= 0 η= 1 η= 3.2

  14. Charged hadrons η= 0 η= 1 3D Hydro (Hirano) η= 3.2 pT Integrated v2 Integrated v2 are derived using the measured spectra and v2(pT). (See a poster by C. Ristea.) Integrated v2 are also relatively flat. <η> <pT> GeV/c 0 0.55 1 0.53 2. h+ 0.506 h- 0.423

  15. Centrality Dependence Centrality dependence at midrapidity Large centrality dependence is seen for pT integrated v2— consistant with PHOBOS results.

  16. Conclusion • v2(pT) for charged hadrons and pions have been measured at midrapidity as well as at forward rapidity. • v2(pT) shows small pseudorapidity dependence—consistent with 3D Hydro model. • η dependence of pT integrated v2 is strongly sensitive to measured spectra. • Strong centrality dependence observed. • Proton and Kaon results are forthcoming.

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