PHOBOS WHITE PAPER REPORT

1. White paper report, June 2004 PHOBOS WHITE PAPER REPORT Wit Busza on behalf of the PHOBOS Collaboration

2. We have discovered a strongly interacting medium with extremely high energy density whose description in terms of simple hadronic degrees of freedom is not appropriate; • Furthermore, we have discovered that much of the data can be expressed in terms of simple scaling rules which suggest the existence of strong global constraints or some kind of universality in the mechanism of the production of hadrons in high energy collisions (possible connection to ideas of parton saturation) • To date, in Heavy Ion Collisions, there is no evidencefor the weakly interactingQGP, as naively imagined by a large segment of the community before RHIC turn-on and concluded from a possible misinterpretation of the lattice results (80% of Stefan-Boltzmann is not weakly interacting)

3. …Key earlyPHOBOS observation…

4. Models prior to RHIC Particle Density near Mid-Rapidity PRL 85, 3100 (2000) PRL 88, 22302 (2002) PRL 91, 052303 (2003) arXiv:nucl-ex/0405027

5. Energy per unit volume: dNch/dh Number of Particles Produced at y=0 <E> ~ 0.7 GeV Therefore total energy released in |h| < 1 is ~2000GeV Energy of Collision “relevant” initial volume ~ pR2 X (0.1fm - few fm) X 2 Initially released energy per unit volume > few GeV/fm3 Note: energy density inside proton ≈ 0.5 GeV/fm3 Data from: PRL 85, 3100 (2000); PRL 88, 22302 (2002); PRL 91, 052303 (2003); arXiv:nucl-ex/0405027

6. In Au+Au Collisions at sNN = 200 GeV • Maximum released energy is at mid-rapidity • In a system at rest with the center of mass • Energy/volume > few GeV/fm3 • It is not appropriate to describe such a system in terms of simplehadronic degrees of freedom

7. AT MID-RAPIDITY THE SYSTEM IS RELATIVELY BARYON-FREE PRC 67, 021901R (2003)

8. …The high energy system is strongly interacting…

9. Evidence from flow: 200 GeV Au+Au PHOBOS preliminary 0 < h < 1.5 0-55% central, h+ + h- PRL 89, 222301 (2002) Nucl. Phys. A715, 611c (2003)

10. Evidence from the small number of particles produced with very low pT: In a large volume, weakly interacting system you would expect the development of particles with long wavelength PHOBOS PHENIX arXiv:nucl-ex/0401006

11. Evidence from the suppression of high-pT particles: PHOBOS d+Au 200 GeV Au+Au 0-6% 200 GeV PRL 91, 072302 (2003)

12. BACK-TO-BACK “JET” CORRELATIONS STAR PRL 90, 082302 (2003)

13. Discovery of simple scaling rules……in other words, discovery of global constraints

14. DISCOVERY OF SIMPLE SCALING BEHAVIORS • UNIVERSAL TOTAL PARTICLE PRODUCTION • ABSENCE OF BOOST INVARIANT CENTRAL PLATEAU • UNIVERSAL SCALING ACCORDING TO “LIMITING FRAGMENTATION” • UNIVERSAL Npart SCALING • FACTORIZATION INTO GEOMETRIC PART AND ENERGY PART

15. UNIVERSAL TOTAL PARTICLE PRODUCTION

16. Relevant energy for comparisons of Au+Au, p+p, and d+Au Brenner et al In pp collisions, on average, approximately half the energy goes into the leading baryon A.Brenner et a., Phys.Rev.D26 (1982) 1497l arXiv:nucl-ex/0301017 arXiv:nucl-ex/0403033

17. arXiv:nucl-ex/0301017

18. ABSENCE OF BOOST INVARIANT CENTRAL PLATEAU

19. E895 E895 E895 3.0 GeV Au+Au NA49 BRAHMS prel. NA49 3.6 GeVAu+Au 4.1 GeVAu+Au 200 GeVAu+Au 8.8 GeVPb+Pb 17.3 GeVPb+Pb PHOBOS Plateau in pseudorapidity distributions is misleading Rapidity distributions of pions are gaussians PRL 91, 052303 (2003) arXiv:nucl-ex/0403050

20. No boost-invariant central plateau for v2 PHOBOS Preliminaryv2200 PHOBOSv2130 PRL 89, 222301 (2002)

21. UNIVERSAL SCALING ACCORDING TO “LIMITING FRAGMENTATION”

22. 6% central dNch/dh ¢/<Npart>/2 Au+Au PRL 91, 052303 (2003)

23. PHOBOS Rest frame of A Rest frame of p or d arXiv:nucl-ex/0403033

25. Energy and pseudorapidity dependence of v2 To be submitted PRL June 2004

26. Limiting fragmentation seen in v2 To be submitted PRL June 2004

27. Elliptic flow: PRL 91, 052303 (2003) To see the limiting behavior, imagine that RHIC collided beams with asymmetric energy, withh´ = -2 corresponding to y = 0.

28. Universal Npart scaling

29. Npart scaling for: pA, KA, pA, dA, AA 10 GeV to 200 GeV Npart from 2 to 350 Preliminary Phobos and E178 data pp chosen to have the same available energy E178: J.E.Elias et al., Phys.Rev.D22(1980) 13 arXiv:nucl-ex/0403033

30. FACTORIZATION INTO GEOMETRIC PART AND ENERGY PART

31. Preliminary arXiv:nucl-ex/0403033

32. Example of factorization into geometric part and energy part: SAME SEEN IN p+A AT ALL ENERGIES arXiv:nucl-ex/0403033

33. Phobos PRL 91, 052303 (2003) Nucl.Phys. A715 (2003) 65-74

34. Centrality Dependence at |h| < 1 Ratio of 200/130 and 200/19.6 PRC 65, 061901R (2002) arXiv:nucl-ex/0405027

35. Energy and geometry factorize arXiv:nucl-ex/0405003

36. We have discovered a strongly interacting medium with extremely high energy density whose description in terms of simple hadronic degrees of freedom is not appropriate; • Furthermore, we have discovered that much of the data can be expressed in terms of simple scaling rules which suggest the existence of strong global constraints or some kind of universality in the mechanism of the production of hadrons in high energy collisions • To date, in Heavy Ion Collisions, there is no evidencefor the weakly interactingQGP, as naively imagined by a large segment of the community before RHIC turn-on and concluded from a possible misinterpretation of the lattice results (80% of Stefan-Boltzmann is not weakly interacting)

37. WE DO NOT CLAIM THE FOLLOWING: • Phenomena unique to RHIC - could be similar to the story of jets • Color deconfinement - exact nature of system unknown • Chiral symmetry restoration

38. SPARES

39. Collaboration (May 2004) 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 Holynski, 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 Wozniak, Alan Wuosmaa, Bolek Wyslouch ARGONNE NATIONAL LABORATORY BROOKHAVEN NATIONAL LABORATORY INSTITUTE OF NUCLEAR PHYSICS PAN, KRAKOW MASSACHUSETTS INSTITUTE OF TECHNOLOGY NATIONAL CENTRAL UNIVERSITY, TAIWAN UNIVERSITY OF ILLINOIS AT CHICAGO UNIVERSITY OF MARYLAND UNIVERSITY OF ROCHESTER

40. dN/dh¢ UA5

41. In a wide variety of systems (hadron + A to A+A) the total number of emitted charged particles appears to scale linearly with the number of participants. • The total multiplicity of charged particles emitted in hadron +A is equal to the number of participants times the multiplicity observed in p+p, while in A+A, the constant of proportionality is the multiplicity produced in e+e- annihilations or in p+p at twice the center of mass energy. This is suggestive of a universal energy dependence of charged particle multiplicities in strong interactions. • In the forward region, the pseudorapidity densities, when measured as a function of the shifted variable eta’=eta-ybeam appear not to depend on beam energy. The precise form of the distribution depends on the impact parameter, but again in an energy- independent way. No evidence is seen for a boost invariant central plateau.