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Flow in AuAu Collisions at RHIC

Flow in AuAu Collisions at RHIC. Marguerite Belt Tonjes University of Maryland for the PHOBOS Collaboration. The Collaboration. Birger Back, Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Abigail Bickley ,

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Flow in AuAu Collisions at RHIC

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  1. Flow in AuAu Collisions at RHIC Marguerite Belt Tonjes University of Maryland for the PHOBOS Collaboration

  2. The Collaboration Birger Back,Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Abigail Bickley, Richard Bindel,Wit Busza (Spokesperson), Alan Carroll, Zhengwei Chai, Patrick Decowski, Edmundo Garcia, Tomasz Gburek, Nigel George, Kristjan Gulbrandsen, Stephen Gushue, Clive Halliwell, Joshua Hamblen,Adam Harrington,Conor Henderson, David Hofman, Richard Hollis, Roman Hołyński, Burt Holzman, Aneta Iordanova, Erik Johnson, Jay Kane, Nazim Khan, Piotr Kulinich, Chia Ming Kuo, Willis Lin, Steven Manly, Alice Mignerey, Gerrit van Nieuwenhuizen, Rachid Nouicer, Andrzej Olszewski, Robert Pak, Inkyu Park, Heinz Pernegger, Corey Reed, Michael Ricci, Christof Roland, Gunther Roland, Joe Sagerer, Iouri Sedykh, Wojtek Skulski, Chadd Smith, Peter Steinberg, George Stephans, Andrei Sukhanov, Marguerite Belt Tonjes, Adam Trzupek, Carla Vale,Siarhei Vaurynovich, Robin Verdier, Gábor Veres, Edward Wenger, Frank Wolfs, Barbara Wosiek, Krzysztof Wožniak, Alan Wuosmaa, Bolek Wysłouch, Jinlong Zhang ARGONNE NATIONAL LABORATORY BROOKHAVEN NATIONAL LABORATORY INSTITUTE OF NUCLEAR PHYSICS, KRAKOW MASSACHUSETTS INSTITUTE OF TECHNOLOGY NATIONAL CENTRAL UNIVERSITY, TAIWAN UNIVERSITY OF ILLINOIS AT CHICAGO UNIVERSITY OF MARYLAND UNIVERSITY OF ROCHESTER M.B.Tonjes, PHOBOS

  3. PHOBOS Collaboration meeting, BNL Chemistry building, October 2002 M.B.Tonjes, PHOBOS

  4. 137000 Silicon Pad Channels Spectrometer 1m Octagon Ring Counters Nearly 4π Coverage f -5.4 -3 0 h +3 +5.4 Detector 2000(2001) M.B.Tonjes, PHOBOS

  5. Why measure flow? • Flow is thought to be generated by compression in the early stages of the collision • Flow probes the thermalization of the system • Elliptic and directed flow probe the evolution of the system M.B.Tonjes, PHOBOS

  6. Flow z Reaction plane M. Kaneta y x v1 v2 Flow measured by decomposing the azimuthal angle particle distributions into Fourier components: directed flow elliptic flow M.B.Tonjes, PHOBOS

  7. Measuring flow in PHOBOS Hit-based method Track-based method h f h • Large h coverage • Event-by-event • Uniform acceptance in  • Separated subevents • Does not require large event sample • Measures pt dependence of v2 • Use of tracks reduces background effects and reduces MC dependence • Subevents and tracks widely separated in h M.B.Tonjes, PHOBOS

  8. v2(Npart) with two methods Hit-based method Track-based method PHOBOS Preliminary 200 GeV AuAu Good agreement h± Nucl.Phys. A715 (2003) 611-614 M.B.Tonjes, PHOBOS

  9. v2 vs. pt AuAu PHOBOS 200 GeV 0-55% central PHOBOS 200 GeV 0-55% central Preliminary Preliminary STAR 130 GeV Reaction Plane 5-53% central STAR 130 GeV 2-cumulant STAR 130 GeV 4-cumulant track-based method v2 h± pt (GeV/c) • Nucl.Phys. A715 (2003) 611-614 M.B.Tonjes, PHOBOS

  10. v2 vs. h at 130 and 200 GeV AuAu () PHOBOS Preliminaryv2200 Minimum Bias () PHOBOSv2130 h± Hit-based method ()Nucl.Phys. A715 (2003) 611-614 v2 has a strong dependence on h () PRL 89, 222301 (2002) M.B.Tonjes, PHOBOS

  11. v2 vs. h at 200 GeV AuAu - centrality dependence peripheral 25-50% midcentral 15-25% central 3-15% width of h bin h± PHOBOS Preliminary Hit-based method M.B.Tonjes, PHOBOS

  12. v2 vs. h at 200 GeV AuAu - comparison of methods v2 v2 v2 PHOBOS Preliminary PHOBOS Preliminary central 3-15% h± peripheral 25-50% h± midcentral 15-25% h± PHOBOS Preliminary Track-based Hit-based Track-based Hit-based Track-based Hit-based h h h M.B.Tonjes, PHOBOS

  13. Hit-based & track-based data combined 8x10-2 PHOBOS Preliminary peripheral 25-50% peripheral 25-50% 6x10-2 midcentral 15-25% midcentral 15-25% central 3-15% central 3-15% 4x10-2 2x10-2 PHOBOS Preliminary • The peripheral data at midrapidity is not flat within 90% confidence level v2 • Different centralities appear to differ only by a scale factor (within errors) h± |h| M.B.Tonjes, PHOBOS

  14. v1 measurement: hit-based method Ring Octagon Ring f h, z v1 • Reaction plane for Octagon calculated from symmetric subevents in the Rings (and vice-versa) M.B.Tonjes, PHOBOS

  15. v1 measured at different energies NA49 PbPb 158 GeV √sNN = 17.2 GeV STAR AuAu √sNN = 200 GeV v1 p± v1 (reflected) h± Minimum Bias y 10-70% central Phys.Rev.C68, 034903, 2003 h nucl-ex/0310029 M.B.Tonjes, PHOBOS

  16. v1 at 19.6 GeV AuAu PHOBOS 6-55% central v1 PHOBOS Preliminary h± h M.B.Tonjes, PHOBOS

  17. v1: 19.6 GeV AuAu & 17.2 GeV PbPb v1 PHOBOS Preliminary PHOBOS AuAu √sNN=19.6 GeV 6-55% h± p± NA49 PbPb √sNN=17.2 GeV Minimum Bias Phys.Rev.C68, 034903, 2003 h M.B.Tonjes, PHOBOS

  18. v1 at 130 GeV AuAu PHOBOS 6-55% central v1 PHOBOS Preliminary h± h (different scale) M.B.Tonjes, PHOBOS

  19. v1 at 200 GeV AuAu PHOBOS 6-55% central v1 PHOBOS Preliminary h± h M.B.Tonjes, PHOBOS

  20. v1 at 200 GeV AuAu:PHOBOS & STAR v1 PHOBOS Preliminary PHOBOS 6-55% central h± STAR AuAu 200 GeV 10-70% central h nucl-ex/0310029 M.B.Tonjes, PHOBOS

  21. v1 at different energies in AuAu v1 v1 v1 PHOBOS Preliminary PHOBOS Preliminary PHOBOS Preliminary h± 6-55% central 19.6 GeV h± 6-55% central 200 GeV h h± 6-55% central h 19.6 GeV 130 GeV 200 GeV h M.B.Tonjes, PHOBOS

  22. v1 19.6, 130, 200 GeV AuAu (h’) dNch/dh’/<Npart>/2 v1 6% central PHOBOS Au+Au PHOBOS Preliminary PRL 91, 052303 (2003) h’ 19.6 GeV 130 GeV 200 GeV h’= h-ybeam h± v1 from positive h used only M.B.Tonjes, PHOBOS

  23. Conclusions • v2 vs pt demonstrates that we do not measure significant non-flow effects • v2 has been measured as a function of h and centrality over a large range in pseudorapidity • v1 has been measured over a range of energies from 19.6 to 200 GeV over a large region of h in PHOBOS • v1 clearly changes behavior from low (19.6 GeV) to high (200 GeV) energy • v1 in the mid-h’ region is reminiscent of limiting fragmentation M.B.Tonjes, PHOBOS

  24. M.B.Tonjes, PHOBOS

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