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Winter Workshop in Nuclear Physics Trelawny Beach, Jamaica March , 2003 steven.manly@rochester

Collective flow with PHOBOS. Steven Manly University of Rochester representing PHOBOS. Why yes, this is a frisbee!. Winter Workshop in Nuclear Physics Trelawny Beach, Jamaica March , 2003 steven.manly@rochester.edu http://hertz.pas.rochester.edu/smanly/.

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Winter Workshop in Nuclear Physics Trelawny Beach, Jamaica March , 2003 steven.manly@rochester

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  1. Collective flow with PHOBOS Steven Manly University of Rochester representing PHOBOS Why yes, this is a frisbee! Winter Workshop in Nuclear Physics Trelawny Beach, Jamaica March , 2003 steven.manly@rochester.edu http://hertz.pas.rochester.edu/smanly/ The view from my office webcam: while I’m here working, my group is enjoying spring break in Rochester Winter Workshop - Jamaica - 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 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 Collaboration meeting, BNL October 2002 Winter Workshop - Jamaica - S. Manly

  3. Flow in PHOBOS Winter Workshop - Jamaica - S. Manly

  4. 5m 2m 5 4 3 2 1 0 1 2 3 4 5 1m h coverage for vtx at z=0 •  coverage • Data at 19.6, 130 and 200 GeV Winter Workshop - Jamaica - S. Manly

  5. Pixelized detector Hit saturation, grows with occupancy Sensitivity to flow reduced Can correct using analogue energy deposition –or- measure of occupied and unoccupied pads in local region assuming Poisson statistics Poisson occupancy correction Winter Workshop - Jamaica - S. Manly

  6. Octagonal detector Require circular symmetry for equal phase space per pixel Pixel’sazimuthalphase space coverage depends on location Acceptance (phase space) weighting Relative phase space weight in annular rings = <Nocc>-1 Winter Workshop - Jamaica - S. Manly

  7. f z + Non-flow background • Non-flow Backgrounds flow signal Dilutes the flow signal • Remove Background • Estimate from MC and correct Winter Workshop - Jamaica - S. Manly

  8. 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 Winter Workshop - Jamaica - S. Manly

  9. Vtx holes RingsN Octagon RingsP Spec holes f h Winter Workshop - Jamaica - S. Manly

  10. High Resolution Low Resolution Determining the collision point octagon hit density peaks at vertex z position extrapolate spectrometer tracks Winter Workshop - Jamaica - S. Manly

  11. Vtx holes Spec holes RingsN Octagon RingsP f h Detector symmetry issues where SPEC vertex efficiency highest Most data taken with trigger in place to enhance tracking efficiency Winter Workshop - Jamaica - S. Manly

  12. RingsN Octagon RingsP f h Limited vertex range along z Offset vtx method Subevents for reaction plane evaluation Technique used for published elliptic flow signal at 130 GeV • Good azimuthal symmetry • Fewer events, no 19.6 GeV data • Gap between subevents relatively small Winter Workshop - Jamaica - S. Manly

  13. RingsN Octagon RingsP Vertex range -10<z<10 f h Full acceptance method Subevents for reaction plane evaluation vary with analysis Technique used for elliptic and directed flow signal at all energies (only directed flow released to date, elliptic flow coming soon) • Good statistics, 19.6 GeV data available • Gap between subevents large • Requires “hole filling” Winter Workshop - Jamaica - S. Manly

  14. Inner layer of vertex detector fills holes in top and bottom. Must map hits from Si with different pad pattern and radius onto a “virtual” octagon Si layer RingsN Octagon RingsP f h Dealing with the holes Winter Workshop - Jamaica - S. Manly

  15. RingsN Octagon RingsP f h Dealing with the holes Fill spectrometer holes by extrapolating hit density from adjoining detectors onto a virtual Si layer. (Actual spec layer 1 is much smaller than the hole in the octagon.) Winter Workshop - Jamaica - S. Manly

  16. RingsN Octagon RingsP Vertex range -8<z<10 f h Track-based method Subevents for reaction plane • Momentum analysis • 200 GeV data • Gap between tracks and subevents large • Little/no background Winter Workshop - Jamaica - S. Manly

  17. Directed flow Charged hadrons 6-55% central AuAu Winter Workshop - Jamaica - S. Manly

  18. 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 19.6 GeV AuAu & 17.2 GeV PbPb h Winter Workshop - Jamaica - S. Manly

  19. v1 at 200 GeV AuAu:PHOBOS & STAR v1 PHOBOS Preliminary PHOBOS 6-55% central h± STAR AuAu 200 GeV 10-70% central h STAR, PRL 92 (2004) 062301 Winter Workshop - Jamaica - S. Manly

  20. In target frame of reference, directed flow exhibits signal consistent with limiting fragmentation Winter Workshop - Jamaica - S. Manly

  21. v2 vs. h at 130 and 200 GeV AuAu () PHOBOS Preliminaryv2200 Minimum Bias h± () PHOBOSv2130 Hit-based method ()Nucl.Phys. A715 (2003) 611-614 () PRL 89, 222301 (2002) Winter Workshop - Jamaica - S. Manly

  22. peripheral 25-50% midcentral 15-25% central 3-15% width of h bin v2 vs. h 200 GeV centrality dependence h± PHOBOS Preliminary Hit-based method Winter Workshop - Jamaica - S. Manly

  23. v2 v2 v2 PHOBOS Preliminary PHOBOS Preliminary peripheral 25-50% h± midcentral 15-25% h± central 3-15% h± PHOBOS Preliminary Track-based Hit-based Track-based Hit-based Track-based Hit-based h h h v2 vs.  200 GeV method comparison Winter Workshop - Jamaica - S. Manly

  24. Combined hit (offset vertex) and track based results for v2 vs. || at 200 GeV (Au-Au) Winter Workshop - Jamaica - S. Manly

  25. v2 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 pt (GeV/c) v2 vs. pt AuAu track-based method v2 h± pt (GeV/c) • Nucl.Phys. A715 (2003) 611-614 Winter Workshop - Jamaica - S. Manly

  26. PHOBOS signal not pt weighted, thus dominated by low pt hits where STAR 2- and 4-particle cumulants have small absolute difference v2 PHOBOS 200 GeV 0-55% central Preliminary STAR 130 GeV Reaction Plane 5-53% central STAR 130 GeV 2-cumulant STAR 130 GeV 4-cumulant pt (GeV/c) Winter Workshop - Jamaica - S. Manly

  27. y vs.  Get a suppression in the spectra which is largest at low pt and small ||. It vanishes at large || and high pt. Gives the famous dip in multiplicity distribution. If integrating v2 over pt, get suppression of the lower pt part (where v2 is small) and the signal should rise. Winter Workshop - Jamaica - S. Manly

  28. ~10% P. Kolb, Proc. of 17th Winter Workshop on Nuclear Dynamics (2001) Transformation of spectra from  to y leads to suppression of multiplicity at low pt and low || This leads to an enhancement of inclusive v2 at mid- T. Hirano, BNL-Riken Workshop on Collective Flow and the QGP (Nov. 2003) Winter Workshop - Jamaica - S. Manly

  29. Limiting fragmentation of elliptic flow PHOBOS Preliminaryv2200 PHOBOSv2130 Winter Workshop - Jamaica - S. Manly

  30. Limiting fragmentation of elliptic flow Scaled by “Kolb factor” PHOBOS Preliminaryv2200 PHOBOSv2130 Winter Workshop - Jamaica - S. Manly

  31. Conclusions • Directed flow measured at 19.6, 130 and 200 GeV • Mild disagreement with STAR about || where v1 kicks in, but both see flat slope at mid- • v1 shows a limiting fragmentation behavior similar to the multiplicity • v2() hit and track results agree. Likely there is very little non-flow correlations. Expect only small difference between v2() and v2(y). • Hint of limiting fragmentation behavior in v2. Expect better results on this soon Winter Workshop - Jamaica - S. Manly

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