Updated Status and Plans of the PHOBOS Experiment

1. Updated Status and Plansof the PHOBOS Experiment Gunther Roland/MIT Presentations to RHIC Planning Group and PAC 12/03 and 12/05 2003

2. Collaboration (Dec 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

3. PHOBOS Future • Complete Baseline Program in the next 3-4 Runs • Essential Items • Long Au+Au Run • Energy Scan (63 GeV + 1 addt’l Energy) • Species Scan (Cu+Cu + 1 addt’l Species) • p+p Reference Data • Budget constraints link near-term and long-term RHIC running considerations

4. 15 Total Publications ~550 citations on SPIRES 10 5 2000 2001 2002 2003 Year Exponential Growth PHOBOS Status

5. RHIC Status • Unique State of Matter formed in Au+Au • Very High Density • Equilibrated Strangeness production • Collective Behavior in Early Stage • Opaque to fast partons • What are the initial conditions that lead to these properties? • Systematic Study vs • Energy Density • System Size • Rapidity, xf • Data continue to surprise us

6. PHOBOS Detector 2004 (+beyond) T0 T0 SpecCal • Final Configuration • Compared to Au+Au Run II: • 15x faster DAQ • 2.5x higher PID reach • new forward Proton Calorimeters • p+p, d+Au Spectrometer Trigger • SpecCal for high pT trigger in Au+Au

7. PHOBOS Capabilities: Multiplicity Array 130 GeV: PRL 89:222301, 2002 PHOBOS preliminary h+ + h-Au-Au data QM’04 Preview Phys. Rev. Lett. 91, 052303 (2003)

8. PHOBOS Capabilities: Spectrometer p QM’04 Preview dE/dx K p p (GeV) Eloss (MeV) p (GeV) Stopping particles ToF dE/dx 0.05 0.5 5.0 pT (GeV/c) Continuous Particle ID from low to high pT

9. PHOBOS Capabilities: Spectrometer Spectrometer Acceptance Acceptance forward of mid-rapidity: 0 < h < 2.5

10. PHOBOS Future • Complete Baseline Program in the next 3-4 Runs • Essential Items • Long Au+Au Run • Energy Scan (63 GeV + 1 addt’l Energy) • Species Scan (Cu+Cu + 1 addt’l Species) • p+p Reference Data • Budget constraints link near-term and long-term RHIC running considerations

11. PHOBOS Future • Complete Baseline Program in the next 3-4 Runs • Essential Items • Long Au+Au Run (Run IV) • Energy Scan (63 GeV + 1 addt’l Energy) • Species Scan (Cu+Cu + 1 addt’l Species) • p+p Reference Data • Budget constraints link near-term and long-term RHIC running considerations must-do items in white paper Crucial Link to d+Au!

12. Charged Hadron dN/dh Distribution in d+Au Comparison to Parton Saturation and RQMD Models Parton saturation model prediction D. Kharzeev et al., hep-ph/0212316 nucl-ex/0311009 (subm.to PRL) First result on d+Au min bias multiplicity Many features reminiscent of lower energy p+A data Important lessons for Saturation Model

13. Charged Hadron dN/dh Distribution in d+Au Comparison to Parton Saturation and RQMD Models nucl-ex/0311009 (subm.to PRL) AMPT/HIJING close to data (-5.4 < h < 4)

14. Particle Ratios in d+Au: p/p vs Centrality Au+Au Phys. Rev. C 67, 021901R (2003) nucl-ex/0309013 - submitted to PRC First particle ratio data from d+Au Constant p/p ratio vs centrality Disagreement with expectations/models

15. d+Au pT Spectra Phys. Rev. Lett. 91, 072302 (2003) d+Au Au+Au

16. RHIC d+Au/Au+Au results conclusively show that high pT suppression at mid-rapidity is unique to Au+Au

17. BRAHMS DNP’03 Preliminary ? Exciting hints in d+Au Need p+p reference data to fully exploit existing d+Au ? ? Vitev, CIPANP’03

18. Scheduling Considerations We considered 27wk/yr, 37wk/yr, 32wk/yr, 37wk/1.5yr, 54wk/2yr scenarios 54wk/2yr scenario not workable Scheduling of energy/species scan early on critical for PHOBOS

19. For many observables rapid change from p+p to peripheral Au+Au large uncertainty in <Npart> for peripheral events Fe+Fe overlaps with well-measured <Npart> range in Au+Au AGS/SPS results on Si+Si vs Pb+Pb show violations of <Npart> scaling Species Scan Au+Au

20. Energy Scan [ ] SPS [ ] RHIC [ ] 2x increase in particle density: Change from high-pT enhancement to strong suppression

21. PHENIX NA49 AGS Energy Scan NA49, SQM’03 Shape of excitation function between SPS and RHIC?

22. Summary • PHOBOS/RHIC Data Set is expanding rapidly • Exciting (and puzzling) results in Au+Au and d+Au • Further insight from • Energy Scan • Species Scan • p+p reference data • Unique contributions from PHOBOS • Multiplicity Array • Spectrometer • Very difficult scheduling • Timing of species/energy scans is crucial to fully exploit PHOBOS (and RHIC) capabilities