1 / 37

Global Observations from PHOBOS A story of scaling

Global Observations from PHOBOS A story of scaling. Mark D. Baker Brookhaven National Laboratory for the Collaboration 8th International Wigner Symposium May 28, 2003. Collaboration (May 2003).

pepin
Download Presentation

Global Observations from PHOBOS A story of scaling

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Global Observations from PHOBOSA story of scaling Mark D. Baker Brookhaven National Laboratory for the Collaboration 8th International Wigner Symposium May 28, 2003 Mark D. Baker

  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 Holynski, 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 Wozniak, Alan Wuosmaa, Bolek Wyslouch, 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 Mark D. Baker

  3. PHOBOS Detector in 2002 Spectrometer RingCounters Octagon Triggering ZDC 12m Be Beampipe ZDC ZDC 1m ZDC Mark D. Baker

  4. Extensive systematic data set Phys. Rev. Lett. (2003), in press, arXiv:nucl-ex/0210015 200 GeV 19.6 GeV 130 GeV PHOBOS PHOBOS PHOBOS dN/dh Typical systematic band (90%C.L.) h h h • d2N/dhdf over 11 x 2p units of hx f • Au+Au at s=19.6, (56), 130, & 200 GeV • p+p and d+Au on the way f h Mark D. Baker

  5. Scaling of rare (hard) processes A L~A1/3 Ncoll = # of NN collisions ~A4/3 (formally Glauber TAA(b)) Npart/2= # of participating nucleons: A Mark D. Baker

  6. _ pp Midrapidity charged particle production Au+Au 200 GeV |h|<1 130 GeV Preliminary 19.6 GeV Collision scaling does NOT disappear at low energy. Problem for naïve “minijet” based models. Mark D. Baker

  7. Initial state parton saturation? QM2002: nucl-ex/0212009 200 GeV 130 GeV Preliminary 19.6 GeV Kharzeev, Levin, Nardi, hep-ph/0111315 l~0.25 from fits to HERA data: xG(x)~x-l Describes energy dependence correctly! Mark D. Baker

  8. Parton Saturation describes AA Kharzeev & Levin, Phys. Lett. B523 (2001) 79 Same l (From HERA) describes dN/dh shape correctly! (& energy & centrality dep.) PRL 87 (2001) Mark D. Baker

  9. Energy Dependence of Central dN/dh Phys. Rev. Lett. (2003), in press, arXiv:nucl-ex/0210015 Scale by Npart/2 & shift to h¢=h- ybeam PHOBOS Au+Au dNch/dh dNch/dh ¢/<Npart> 6% central PHOBOS Au+Au Systematic errors not shown The “fragmentation region” extent grows with sNN Mark D. Baker

  10. “xF scaling” in AuAu UA5, Z.Phys.C33, 1 (1986) p + p inel. dNch/dh ¢/<Npart> 6% central dN/dh¢ PHOBOS Au+Au 19.6 GeV is preliminary Systematic errors not shown Mark D. Baker

  11. Nch scales with Npart e+e- e+e- Error bands due to high-h extrapolation Au+Au e+e- nucl-ex/0301017 (preliminary) Total charged particle production ~ Npart Mark D. Baker

  12. AA and e+e- similar in shape as well as magnitude 200 GeV e+e- measures dN/dyT(rapidity relative to“thrust” axis) Mark D. Baker

  13. Comparison of áNchñ vs. Energy nucl-ex/0301017 pQCD e+e- Calculation  nucl-ex/0301017; Submitted for Publication Mark D. Baker

  14. Different systems converge at high energy. Comparison of áNchñ vs. Energy PHOBOS Preliminary Central Au+Au e+e- pp (pp) data @ seff Central AA nucl-ex/0301017 1 10 102 103 s (GeV) Universality? Mark D. Baker

  15. PT Distribution of Charged Particles AuAu Phobos Preliminary Systematic Errors not shown  Phobos measures from pT, = 0.030 – 5 GeV/c & beyond Mark D. Baker

  16. Comparing Au+Au spectra to pp Mark D. Baker

  17. Ratio of Au+Au and pp spectra at 200 GeV • High pT hadrons don’t scale like Ncoll either! mid-peripheral Npart = 65 ± 4 Npart = 344 ± 12 central arXiv:nucl-ex/0302015 Mark D. Baker

  18. A-dependence of Charged Spectra • Normalize by <Npart>/2 • Divide by the value at Npart=65 Mark D. Baker

  19. Normalize by Npart/2. Divide by the value at Npart=65 Collision scaling would imply: PHOBOS nucl-ex/0301017 Au+Au 200 GeV UA1 pp (200 GeV) Particle Production Scales with Nparteven at high pT Mark D. Baker

  20. Approximate Npart scaling at high pT is MAXIMAL suppression! Ncoll *S / V ~ Npart4/3 / L ~ Npart Only hadrons produced on the surface survive! NOTE: Very peripheral collisions should recover Ncoll scaling Mark D. Baker

  21. Is final state “jet quenching” the only explanation? Kharzeev, Levin, McLerran hep-ph/0210332 Particle Yield/<Npart/2> Initial state parton saturation works too ... Mark D. Baker

  22. How do we resolve this? • Strong (maximal) final state suppression at high pT? • Indication of high density strongly interacting matter! • Strong initial state suppression persisting to moderately high pT? • Indication of multipartonic effects in the nuclear wavefunction! dAu data! Prediction: Saturation: RdAu ~ 0.75 for 15% central dAu Kharzeev, Levin, Nardi hep-ph/0212316 Mark D. Baker

  23. dN/dh/<Npart> (h~0) Pseudorapidity <Npart> “Truth” Centrality determination in d+Au HIJING d+Au MC HIJING d+Au MC Centrality in d+Au: Handle with care! Mark D. Baker

  24. Centrality cuts (4 bins) 0 – 20% 0.2<h<1.4 20 – 40% 40 – 70% 3.0<|h|<5.4 70 – 100% PHOBOS d+Aupreliminary Counts Centrality Npart 70-100% 3.3 ± 1 ADC Signal Sum (arb. units ) 40-70% 6.8 ± 2 20-40% 11 ± 1.5 0-20% 16 ± 2.5 Preliminary Results from d+Au Mark D. Baker

  25. PHOBOSpreliminary PHOBOS preliminary Yield/<Npart/2>/p+p fit Yield/<Npart/2>/p+p fit RdAu RdAu PHOBOS preliminary PHOBOS preliminary Preliminary Results from d+Au Mark D. Baker

  26. PHOBOSpreliminary PHOBOS preliminary Yield/<Npart/2>/p+p fit Yield/<Npart/2>/p+p fit RdAu RdAu PHOBOS preliminary PHOBOS preliminary Preliminary Results from d+Au KLN Saturation Mark D. Baker

  27. Global Observations from PHOBOS • Empirical Scaling Rules • Overall particle production in AuAu (low pT): • “Hard” component does not grow with energy. • Limiting fragmentation (“xF scaling”) seen in AuAu. • Overall particle production scales like Npart • Particle production/participant pair looks like e+e- • Behavior at moderately high pT • Maximal suppression from Ncoll scaling in AuAu. • Ncoll scaling (or slight enhancement) in dAu • Centrality dependence in dAu • Ncoll scaling even for 20% most central data! • Increasing suppression from Ncoll scaling at low pT Mark D. Baker

  28. Conclusions • PHOBOS “scaling rules” provide many pieces of the puzzle. • The latest news from PHOBOS: • We have compared central AuAu to central dAu. • This data strongly disfavors the “initial state” parton saturation interpretation of high pT hadron suppression. Mark D. Baker

  29. Backup slides Mark D. Baker

  30. This Year: PHOBOS Detector 2003 T0 T0 mini-pCal SPECTRIG  Moved TOF walls back ~ 5 m from interaction point  Installed new spectrometer trigger detector that selects on high pT tracks pCal  Installed new “time-zero” (T0) Cerenkov detectors to provide triggering and on-line vertexing as well as a start time for our TOF walls.  Proton calorimeter on Gold and Deuteron “going” sides for dA run Mark D. Baker

  31. Initial state parton saturation? See Iancu, Leonidov, McLerran hep-ph/0202270 • Gluon density cannot grow indefinitely. • Non-Abelian diagram ggg kicks in at low x or low k. Mark D. Baker

  32. Centrality scaling in pT bins (Au+Au) • Spectra normalized to a fit at mid-peripheral 45-50% bin.  Over the centrality range studied, for low and high pT, the Au+Au data scale approximately with number of participants.  nucl-ex/0302015; Submitted for Publication Mark D. Baker

  33. Spectrometer Performance Acceptance Momentum Resolution • Data Sample Production Run 2001(200 GeV) • 7.8 M Au+Au Events, Min. Bias Trigger • 32 M reconstructed particles Mark D. Baker

  34. b b Peripheral Central x 2 6 4 2 Centrality Determination (AuAu) Data • HIJING +GEANT • Glauber calculation • Model of paddle trigger Paddle signal Data+MC Nparticipants Mark D. Baker

  35. PHOBOS Preliminary Results from d+A PHOBOSpreliminary PHOBOS preliminary RdAu RdAu PHOBOS preliminary PHOBOS preliminary Mark D. Baker

  36. Remove the “Leading Proton” Effect seff s Basile et al (1980-1984) pQCD e+e- Calculation (A. Mueller, 1983) Mark D. Baker

  37. Many ways to slice pz Rapidity: Generalized velocity Feynman x: scaled pz Pseudorapidity: ~y: easier to measure Mark D. Baker

More Related