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Au-Au event in the PHOBOS detector

Au-Au event in the PHOBOS detector. Energy dependence of elliptic flow over a large pseudorapidity range in Au+Au collisions at RHIC. Steven Manly University of Rochester Representing the PHOBOS Collaboration.

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Au-Au event in the PHOBOS detector

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  1. Au-Au event in the PHOBOS detector Energy dependence of elliptic flow over a large pseudorapidity range in Au+Au collisions at RHIC Steven Manly University of Rochester Representing the PHOBOS Collaboration BNL - Elliptic Flow, S. Manly

  2. Birger Back,Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Abigail Bickley, Richard Bindel, Wit Busza (Spokesperson), Alan Carroll, Zhengwei Chai, Patrick Decowski, Edmundo García, Tomasz Gburek, Nigel George, Kristjan Gulbrandsen, Clive Halliwell, Joshua Hamblen, Adam Harrington, Michael Hauer, Conor Henderson, David Hofman, Richard Hollis, Roman Hołyński, Burt Holzman, Aneta Iordanova, 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, Christof Roland, Gunther Roland, Joe Sagerer, Helen Seals, Iouri Sedykh, Wojtek Skulski, Chadd Smith, Maciej Stankiewicz, Peter Steinberg, George Stephans, Andrei Sukhanov, Marguerite Belt Tonjes, Adam Trzupek, Carla Vale, Sergei Vaurynovich, Robin Verdier, Gábor Veres, Peter Walters, Edward Wenger, Frank Wolfs, Barbara Wosiek, Krzysztof Woźniak, Alan Wuosmaa, Bolek Wysłouch 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 Collaboration meeting, BNL October 2002 BNL - Elliptic Flow, S. Manly

  3. “Flow” = patterns in the energy, momentum, or particle density distributions that we use to ferret out clues as to the nature of the collision/matter To what extent is the initial geometric asymmetry mapped into the final state? View along beamline BNL - Elliptic Flow, S. Manly

  4. Flow as an experimental probe • Sensitive to interaction strength View along beamline • Sensitive to very early times and particle velocities since asymmetry disappears with time • With sufficient  coverage, it probes longitudinal uniformity of system BNL - Elliptic Flow, S. Manly

  5. Flow quantified Best estimate  event plane (reaction plane) Poskanzer and Voloshin, Phys. Rev. C58 (1998) 1671 View along beamline dN/d(f -YR ) = N0 (1 + 2V1cos (f-YR) + 2V2cos (2(f-YR) + ... ) Fourier decomposition of the azimuthal multiplicity distribution BNL - Elliptic Flow, S. Manly

  6. Flow quantified (reaction plane) Directed flow View from above View alongbeamline dN/d(f -YR ) = N0 (1 + 2V1cos (f-YR) + 2V2cos (2(f-YR) + ... ) BNL - Elliptic Flow, S. Manly

  7. Flow quantified (reaction plane) Elliptic flow View alongbeamline dN/d(f -YR ) = N0 (1 + 2V1cos (f-YR) + 2V2cos (2(f-YR) + ... ) BNL - Elliptic Flow, S. Manly

  8. Flow quantified (reaction plane) Higher terms View alongbeamline dN/d(f -YR ) = N0 (1 + 2V1cos (f-YR) + 2V2cos (2(f-YR) + ... ) BNL - Elliptic Flow, S. Manly

  9. b (reaction plane) n=2, elliptic flow View along beamline BNL - Elliptic Flow, S. Manly

  10. Hydrodynamic limit STAR: PRL86 (2001) 402 PHOBOS preliminary ||<1 Thanks to M. Kaneta (PHOBOS : Normalized Paddle Signal) Flow at RHIC to date (a few highlights) Elliptic flow is large near =0 (relative to hydro limit) BNL - Elliptic Flow, S. Manly

  11. PRL 91 (2003) 182301 Flow at RHIC to date (a few highlights) Elliptic flow is large near =0 (relative to hydro limit) V2(pT) grows with pT at low pT, consistent with hydro BNL - Elliptic Flow, S. Manly

  12. PHOBOS 200 GeV 0-55% central v2 Preliminary Preliminary STAR 130 GeV Reaction Plane 5-53% central STAR 130 GeV 2-cumulant STAR 130 GeV 4-cumulant pT (GeV/c) Flow at RHIC to date (a few highlights) Elliptic flow is large near =0 (relative to hydro limit) V2(pT) grows with pT at low pT, consistent with hydro V2(pT) saturates at high pT BNL - Elliptic Flow, S. Manly

  13. Flow at RHIC to date (a few highlights) Elliptic flow is large near =0 (relative to hydro limit) V2(pT) grows with pT at low pT, consistent with hydro V2(pT) saturates at high pT nucl-ex/0306007 Xhangbu Xu, Quark Matter 2004 Partonic energy loss plus quark coalescence may explain saturation and meson-baryon difference BNL - Elliptic Flow, S. Manly

  14. T.Hirano, K.Tsuda, PRC66,054905(2002). Flow at RHIC to date (a few highlights) Elliptic flow is large near =0 (relative to hydro limit) V2(pT) grows with pT at low pT, consistent with hydro V2(pT) saturates at high pT Partonic energy loss plus quark coalescence may explain saturation and meson-baryon difference Elliptic flow falls off sharply as a function of || BNL - Elliptic Flow, S. Manly

  15. Flow at RHIC to date (a few highlights) Elliptic flow is large near =0 (relative to hydro limit) V2(pT) grows with pT at low pT, consistent with hydro V2(pT) saturates at high pT Partonic energy loss plus quark coalescence may explain saturation and meson-baryon difference Elliptic flow falls off sharply as a function of || n2 terms observed BNL - Elliptic Flow, S. Manly

  16. Strongly interacting dense matter! Partonic? Longitudinal structure of the collision not trivially understood Flow at RHIC to date (a few highlights) Elliptic flow is large near =0 (relative to hydro limit) V2(pT) grows with pT at low pT, consistent with hydro V2(pT) saturates at high pT Partonic energy loss plus quark coalescence may explain saturation and meson-baryon difference Elliptic flow falls off sharply as a function of || n2 terms observed Systematic study of v2(E,) probes the longitudinal dynamics of the collision This work  BNL - Elliptic Flow, S. Manly

  17. Flow in PHOBOS BNL - Elliptic Flow, S. Manly

  18. 5m 2m 5 4 3 2 1 0 1 2 3 4 5 1m h coverage for vtx at z=0 Large  coverage Data at 19.6, 62.4, 130 and 200 GeV BNL - Elliptic Flow, S. Manly

  19. -2.0 < h < -0.1 0.1 < h < 2.0 Yna Ynb SubE (a) SubE (b) Flow: basic method • Subevent technique: correlate event plane in one part of detector to  asymmetry in track pattern in other part of detector • Correct for imperfect reaction plane resolution  dependence of the multiplicity BNL - Elliptic Flow, S. Manly

  20. Pixelized detector Hit saturation, grows with occupancy Sensitivity to flow reduced Can correct using analog energy deposition –or- measure of occupied and unoccupied pads in local region assuming Poisson statistics BNL - Elliptic Flow, S. Manly

  21. f z + Azimuthally symmetric background Azimuthally symmetric backgrounds flow signal Dilutes the flow signal • Remove Background • Estimate from MC and correct BNL - Elliptic Flow, S. Manly

  22. Detector Beampipe dE (keV) cosh h Background! h Background suppression Demand energy deposition be consistent with angle Works well in Octagon Technique does not work in rings because angle of incidence is ~90 BNL - Elliptic Flow, S. Manly

  23. Vtx holes RingsN Octagon RingsP Spec holes f h BNL - Elliptic Flow, S. Manly

  24. RingsN Octagon RingsP Vertex range -10<z<10 f h Hit-based method Subevents for reaction plane evaluation BNL - Elliptic Flow, S. Manly

  25. RingsN Octagon RingsP f h Flow: method continued Determine event plane in each subevent, 2± Method from Poskanzer and Voloshin, Phys. Rev. C58 (1998) 1671 BNL - Elliptic Flow, S. Manly

  26. RingsN Octagon RingsP f h Flow: method continued Correlate 2± with hits outside of given subevent to get raw v2 Method from Poskanzer and Voloshin, Phys. Rev. C58 (1998) 1671 BNL - Elliptic Flow, S. Manly

  27. RingsN Octagon RingsP f h Flow: method continued Determine event plane resolution by correlating 2+ and 2- Method from Poskanzer and Voloshin, Phys. Rev. C58 (1998) 1671 BNL - Elliptic Flow, S. Manly

  28. RingsN Octagon RingsP f h Flow: method continued Correct raw v2 by resolution (factor of 1.7 to 3 depending on energy and centrality, well understood) Correction determined from data Method from Poskanzer and Voloshin, Phys. Rev. C58 (1998) 1671 BNL - Elliptic Flow, S. Manly

  29. Resolution-corrected v2 is further corrected by ~30% • dilution due to azimuthally symmetric background • effects due to residual bias in 2± due to hole filling RingsN Octagon RingsP f Correction derived from Monte Carlo h Flow: method continued BNL - Elliptic Flow, S. Manly

  30. RingsN Octagon RingsP f h Flow: method continued • Have agreement between: • Two hit-based analyses  one “holy”, one not • Track-based analysis with NO background BNL - Elliptic Flow, S. Manly

  31. v2 vs.  (four energies) Bars are 1 “statistical” errors, expect some correlation (0-40% central Au+Au data) BNL - Elliptic Flow, S. Manly

  32. v2 vs.  (four energies) Boxes are 90% C.L. systematic errors (0-40% central Au+Au data) BNL - Elliptic Flow, S. Manly

  33. v2 vs.  (four energies) Shape is triangular at all four energies, no evidence of plateau (0-40% central Au+Au data) BNL - Elliptic Flow, S. Manly

  34. v2 vs.  (four energies) Drop highest || points at 19.6 GeV in following results (0-40% central Au+Au data) BNL - Elliptic Flow, S. Manly

  35. Systematic errors Hit definition Beam orbit/alignment Subevent definition Transverse vertex position cut Bins for weighting matrix definition Dead channel correction algorithm Poisson occupancy correction algorithm Hole filling alogorithm Knowledge of azimuthally symmetric background dN/d shape Symmetry in  BNL - Elliptic Flow, S. Manly

  36. v2 vs.  (four energy overlay) Preliminary Au+Au data (0-40% central) Only statistical errors shown BNL - Elliptic Flow, S. Manly

  37. Preliminary Au+Au data (0-40% central) Evolution of v2 with energy BNL - Elliptic Flow, S. Manly

  38. Limiting fragmentation Take out differing beam boosts by going into approximate frame of reference of target Look at ’ scaling PHOBOS Au+Au results PRL 91, 052303 (2003) “limiting fragmentation”  energy independence in ’=||-ybeam BNL - Elliptic Flow, S. Manly

  39. y vs.  Boost invariant spectra transform as: Jacobian suppresses spectra at low , low pT, and for large mass BNL - Elliptic Flow, S. Manly

  40. y vs. : effect on multiplicity dN/d dN/dy 0 BNL - Elliptic Flow, S. Manly

  41. y vs. : effect on v2 P. Kolb, Proc. of 17th Winter Workshop on Nuclear Dynamics (2001) Near mid-rapidity, integration over pT weights flow to higher pT due to suppression at low pT  v2() larger than v2(y) BNL - Elliptic Flow, S. Manly

  42. y vs. : effect on v2 V2() V2(y) 0 No change in the qualitative features of the result (<15% at =0) BNL - Elliptic Flow, S. Manly

  43. Limiting fragmentation and elliptic flow Preliminary Au+Au data (0-40% central) Only statistical errors shown BNL - Elliptic Flow, S. Manly

  44. Limiting fragmentation and elliptic flow Preliminary Au+Au data (0-40% central) ’=||-ybeam Only statistical errors shown BNL - Elliptic Flow, S. Manly

  45. Conclusions No boost invariant plateau over a broad region of || BNL - Elliptic Flow, S. Manly

  46. Preliminary Au+Au data (0-40% central) Conclusions No boost invariant plateau over a broad region of || Linear logarithmic growth with center-of-mass energy in differing regions of || BNL - Elliptic Flow, S. Manly

  47. Preliminary Preliminary Au+Au data (0-40% central) Au+Au data Conclusions No boost invariant plateau over a broad region of || Linear logarithmic growth with center-of-mass energy in differing regions of || No sharp changes in the dynamics of particle production in pseudorapidity or beam energy BNL - Elliptic Flow, S. Manly

  48. Preliminary Au+Au data (0-40% central) Conclusions No boost invariant plateau over a broad region of || Linear logarithmic growth with center-of-mass energy in differing regions of || No sharp changes in the dynamics of particle production in pseudorapidity or beam energy Preliminary Au+Au data BNL - Elliptic Flow, S. Manly

  49. Au-Au event in the PHOBOS detector BNL - Elliptic Flow, S. Manly

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