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Recent Results from PHOBOS

Recent Results from PHOBOS. David Hofman University of Illinois at Chicago For the Collaboration. 7 th CMS Heavy Ion Meeting June 8-11, 2003, Delphi. Collaboration (May 2003).

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Recent Results from PHOBOS

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  1. Recent Results from PHOBOS David Hofman University of Illinois at Chicago For the Collaboration 7th CMS Heavy Ion MeetingJune 8-11, 2003, Delphi

  2. Collaboration (May 2003) Birger Back,Mark Baker, Maarten Ballintijn, Donald Barton, Bruce Becker, Russell Betts, Abigail Bickley, Richard Bindel, Andrzej Budzanowski, Wit Busza (Spokesperson), Alan Carroll, 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,Jang Woo Lee, Willis Lin, Steven Manly, Alice Mignerey, Gerrit van Nieuwenhuizen, Aaron Noell, Rachid Nouicer, Andrzej Olszewski, Robert Pak, Inkyu Park, Heinz Pernegger, Corey Reed, Louis Remsberg, Christof Roland, Gunther Roland, Joe Sagerer, Pradeep Sarin, Pawel Sawicki, Iouri Sedykh, Wojtek Skulski, Chadd Smith, Peter Steinberg, George Stephans, Andrei Sukhanov, Ray Teng, Marguerite Belt Tonjes, Adam Trzupek, Carla Vale, Robin Verdier, Gábor Veres, Bernard Wadsworth, Frank Wolfs, Barbara Wosiek, Krzysztof Woźniak, 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 7th CMS - Heavy Ion Meeting, Delphi

  3. The PHOBOS Detector in 2002 Spectrometer Ring Counters Octagon f Triggering -5.4 -3 0 +3 +5.4 h ZDC 137000 Silicon Pad Channels 1m Nearly 4pCoverage ZDC 7th CMS - Heavy Ion Meeting, Delphi

  4. PHOBOS Data on dN/dh in Au+Auvs. Centrality and s 200 GeV 19.6 GeV 130 GeV PHOBOS PHOBOS PHOBOS dN/dh Typical systematic band (90%C.L.) h h h  Extensive systematic multiplicity data set. 7th CMS - Heavy Ion Meeting, Delphi

  5. b b Peripheral Central Reminder: Centrality in Au+Au Data Paddle: Multiplicity in 3 < |h| < 4.5 • HIJING +GEANT • Glauber calculation • Model of paddle trigger Paddle signal Data+MC Npart 7th CMS - Heavy Ion Meeting, Delphi

  6. A L~A1/3 “Participant” Scaling Npart/2= # of participating nucleons: A “Collision” Scaling Ncoll = # of NN collisions: ~A4/3 7th CMS - Heavy Ion Meeting, Delphi

  7. sinel=42 mb (RHIC) sinel=33 mb (SPS) sinel=21 mb (AGS) Number of Collisions at Different Energies Au+Au n = Ncoll/(Npart/2) Glauber Monte Carlo 7th CMS - Heavy Ion Meeting, Delphi

  8. Energy Dependence of Central Yields at h=0 A + A For central 6% collisions at midrapidity for RHIC full energy • Extrapolations to LHC for central collisions dNch/dh at |h|<1 are ~ 1300-2200 (factor 1.7-2.8 increase over RHIC) 7th CMS - Heavy Ion Meeting, Delphi

  9. Energy Dependence of Central dN/dh shape PHOBOS Au+Au dNch/dh 6% central dNch/dh ¢/<Npart>/2 PHOBOS Au+Au Systematic errors not shown Scale by <Npart>/2 & shift to h¢=h- ybeam Phys. Rev. Lett. (2003), in press  See a clear ‘Universal’ Fragmentation Region at Rest Frame of one Ion. 7th CMS - Heavy Ion Meeting, Delphi

  10. Fragmentation Region Comparison UA5, Z.Phys.C33, 1 (1986) p + p inel. dN/dh¢ PHOBOS Au+Au 6% central dNch/dh ¢/<Npart>/2 Systematic errors not shown  Growth of the Fragmentation Region with sNN • What Happens at LHC? 7th CMS - Heavy Ion Meeting, Delphi

  11. Charged Particle Production at Midrapidity Energy and Centrality Dependence PRC 65, 061901(R) (2002); 19.6 GeV in Preparation Midrapidity |h|<1 Au+Au 200 GeV dNch/dh 130 GeV 19.6 GeV preliminary pp two component fit with x~ 0.1  See same fraction of about 10% collision scaling fits all energies. 7th CMS - Heavy Ion Meeting, Delphi

  12. Charged Particle Production at Midrapidity Energy and Centrality Dependence Midrapidity |h|<1 Data is normalized by corresponding pp value for each energy. 200 GeV Au+Au dNch/dh 130 GeV 19.6 GeV preliminary pp  Surprising: ratio of hard/soft collisions is the same. • What Happens at LHC? 7th CMS - Heavy Ion Meeting, Delphi

  13. Au+Au Centrality Dependence of Total Nch Error bands due to high-h extrapolation (preliminary)  Total charged particle production ~ Npartand consistent with e+e- 7th CMS - Heavy Ion Meeting, Delphi

  14. Compare Shapes of AA and e+e- 200 GeV e+e- measures dN/dyT(rapidity relative to“thrust” axis)  AA and e+e- similar in shape as well as magnitude. 7th CMS - Heavy Ion Meeting, Delphi

  15. Comparison of Total áNchñ vs. Energy nucl-ex/0301017 pQCD e+e- Calculation  Surprising agreement at high energy 7th CMS - Heavy Ion Meeting, Delphi

  16. Different systems converge at high energy. Comparison of Total áNchñ vs. Energy PHOBOS Preliminary Central Au+Au e+e- LHC ? pp (pp) data @ seff Central AA nucl-ex/0301017 1 10 102 103 s (GeV) • Universality? An Accident? LHC&CMS could confirm this. 7th CMS - Heavy Ion Meeting, Delphi

  17. Charged Particle Elliptic Flow at 130 GeV dN/d(f -YR ) = N0 (1 + 2v1cos (f-YR) + 2v2cos (2(f-YR)) + ... ) PRL 89, 222301 (2002) • Centrality dependence of v2 at mid-rapidity reaches the hydrodynamic limit for central collisions. • Systematic drop in v2 as a function of h, reaches hydro limit for central pseudorapidity.  Bulk collective flow indicates high density phase and hydro limit for v2 indicates short timescale. Hydrodynamic limit schematic illustration  Lack of boost invariance. Poses a challenge for theory. 7th CMS - Heavy Ion Meeting, Delphi

  18. Preliminaryv2200 Final v2130 v2 vs. h and Energy <Npart>~190 v2 PRL 89, 222301 200 130 PHOBOS Au-Au h  PRELIMINARY 200 GeV results very similar to 130 GeV • What Happens at LHC? 7th CMS - Heavy Ion Meeting, Delphi

  19. Particle Ratios: Energy Dependence pT = 0.07 – 1.0 GeV/c A+A central collisions PHOBOS 130 GeVPRL 87,102301,2001 K–/K+ p/p PHOBOS 200 GeVPRC 67, 021901(R), 2003  At RHIC see a rapidly decreasing net baryon density near midrapidity. • What Happens at LHC? 7th CMS - Heavy Ion Meeting, Delphi

  20. Energy evolution of B Using measured <K–>/<K+>,<p>/<p> and statistical model of F. Becattiniet al.,(PRC64,024901,2001) with Tch 160 – 170 MeV Estimated baryochemical potential at sNN = 200 GeV: B = 26  2 MeV • LHC ~ 1 MeV? Fit: P.Braun-Munzinger NP. A697,902,2002 7th CMS - Heavy Ion Meeting, Delphi

  21. PT Distribution of Charged Particles “Soft” part of spectrum Phobos Preliminary Systematic Errors not shown  What about high pT? Have a quick look at the “Hard” part of the spectrum. 7th CMS - Heavy Ion Meeting, Delphi

  22. Transverse Momentum Distributionsfor Au+Au @ 200 GeV Centrality Npart 45-50% 65 ± 4 35-45% 93 ± 5 25-35% 138 ± 6 15-25% 200 ± 8 6-15% 276 ± 9 0-6% 344 ± 12 Centrality range: <b> from 10 to 3 fm <> from 3 to 6 0.2<yp<1.4 nucl-ex/0302015 Submitted to Phys Lett B 7th CMS - Heavy Ion Meeting, Delphi

  23.  Excess yield at 2 GeV/c  BUT, at higher energy the particle yields appear to come back ‘down’ to the pp value. Comparing Au+Au Spectra to pp 7th CMS - Heavy Ion Meeting, Delphi

  24. Ratio of Au+Au and pp Spectra at 200 GeV • We observe a significant change in the spectral shape between pp and Au+Au collisions already for mid-peripheral events. • Central Au+Au collisions show a strong violation of (expected) collision scaling at high pT. mid-peripheral Npart = 65 ± 4 n ~3 n ~6 central Npart = 344 ± 12 7th CMS - Heavy Ion Meeting, Delphi

  25. Preliminary Results from d+Au Transverse Momentum Distributions in d+Au Centrality Determination:Energy in Silicon Ring Counters 0 – 20% 0.2<h<1.4 20 – 40% 3.0<|h|<5.4 PHOBOS d+Aupreliminary 40 – 70% Counts 70 – 100% Energy (arb. units ) Centrality Npart 70-100% 3.3 ± 1 40-70% 6.8 ± 2 20-40% 11 ± 1.5 0-20% 16 ± 2.5 7th CMS - Heavy Ion Meeting, Delphi

  26. Yield/<Npart/2>/p+p fit Yield/<Npart/2>/p+p fit PHOBOS Preliminary Results from d+Au PHOBOSpreliminary PHOBOS preliminary RdAu (Yield AA/pp assuming collision scaling) peripheral RdAu PHOBOS preliminary PHOBOS preliminary central 7th CMS - Heavy Ion Meeting, Delphi

  27. Global Observations from PHOBOS at RHIC (That would be very interesting to measure at LHC) • Overall particle production in Au+Au (low pT): • At midrapidity, the fraction of “Hard” to “Soft” component stays at about 10% from 19.6 to 200 GeV • Limiting fragmentation seen in Au+Au • Overall particle production scales like Npart • Particle production/participant pair looks like e+e- • Behavior at moderately high pT • Suppression from Ncoll scaling in Au+Au • Ncoll scaling (or slight enhancement) in d+Au 7th CMS - Heavy Ion Meeting, Delphi

  28. Backup Slides

  29. Yield/<Npart/2>/p+p fit Yield/<Npart/2>/p+p fit PHOBOS Preliminary Results from d+A PHOBOSpreliminary PHOBOS preliminary RdAu RdAu PHOBOS preliminary PHOBOS preliminary 7th CMS - Heavy Ion Meeting, Delphi

  30. Approximate Npart scaling at high pT is MAXIMAL suppression! Ncoll *S / V ~ Npart4/3 / L ~ Npart From Mark Baker Only hadrons produced on the surface survive! NOTE: Very peripheral collisions should recover Ncoll scaling 7th CMS - Heavy Ion Meeting, Delphi

  31. Determine to what extent the initial state spatial anisotropy is mapped into the final state particle production. Charged Particle Asimuthal Distribution Elliptic Flow YR dN/d(f -YR ) = N0 (1 + 2v1cos (f-YR) + 2v2cos (2(f-YR)) + ... ) 7th CMS - Heavy Ion Meeting, Delphi

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