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Systematics of Soft Particle Production at RHIC:

Systematics of Soft Particle Production at RHIC:. Lessons from. (And some thoughts for the future). George S.F. Stephans Massachusetts Institute of Technology. Detector. Theory 1999. Theory 2000. PHOBOS 2001. Theory 2000. PHOBOS 2000. PHOBOS 2001.

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Systematics of Soft Particle Production at RHIC:

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  1. Systematics of Soft Particle Production at RHIC: Lessons from (And some thoughts for the future) George S.F. Stephans Massachusetts Institute of Technology

  2. Detector XLII Rencontres de Moriond La Thuile, Italy 24-Mar-2007 George S.F. Stephans

  3. Theory 1999 Theory 2000 PHOBOS 2001 Theory 2000 PHOBOS 2000 PHOBOS 2001 PHOBOS 2000 Energy dependence of particle production:First RHIC physics result Theory 1999 Phys.Rev.Lett. 88 (2002) 22302 Phys.Rev.Lett. 85 (2000) 3100 XLII Rencontres de Moriond La Thuile, Italy 24-Mar-2007 George S.F. Stephans

  4. Impact of first measurement • Invalidated many of the theoretical predictions in existence • Provided support for further development of theories of parton saturation • If theory is validated, this process may dominate low-x physics at high enough energy, even in p+p • Implied that tracking and other measurements in heavy ion collisions at the LHC may not be as horrendous as previously thought • Furthermore, found that dN/d per participant pair in Au+Au is equal to dN/d in p+p at twice the center of mass energy (next slide). XLII Rencontres de Moriond La Thuile, Italy 24-Mar-2007 George S.F. Stephans

  5. A+A, p+p, & e++e- energy dependence What will happen at the LHC (p+p@14 TeV, A+A@5.5 TeV)? Correspondence between e++e- and p+p@(s)/2 known for some time. Phys. Rev. C74, 021902(R) (2006) XLII Rencontres de Moriond La Thuile, Italy 24-Mar-2007 George S.F. Stephans

  6. Scale by Npart/2 Shift to h¢ = h - ybeam PHOBOS Au+Au 6% central dNch/dh dNch/dh ¢/<Npart/2> PHOBOS Au+Au Effectively viewed in rest frame of one nucleus Pseudorapidity dependence  I Phys.Rev.Lett. 91 (2003) 052303 XLII Rencontres de Moriond La Thuile, Italy 24-Mar-2007 George S.F. Stephans

  7. Pseudorapidity dependence  II Called “extended longitudinal scaling” and “limiting fragmentation” Energy and pseudorapidity dependencies factorize Phys.Rev. C74 (2006) 021901 Nucl.Phys. A774 (2006) 113 XLII Rencontres de Moriond La Thuile, Italy 24-Mar-2007 George S.F. Stephans

  8. central data Pseudorapidity dependence  III LHC prediction dNch/dh ¢/<Npart/2> Acta Phys. Pol. 35 (2004) 2873 XLII Rencontres de Moriond La Thuile, Italy 24-Mar-2007 George S.F. Stephans

  9. Pseudorapidity dependence  IV A similar effect is seen for elliptic flow Au-Au data, h± However, v2 at =0 in 200 GeV Au+Au is claimed to approach the hydro limit v2 0-40% centrality Systematic errors only What will happen at the LHC??? '=||-ybeam Phys.Rev.Lett. 94 (2005) 122303 XLII Rencontres de Moriond La Thuile, Italy 24-Mar-2007 George S.F. Stephans

  10. Centrality dependence  I • Impact parameter varies in heavy ion collisions: Not just “more of the same” • Large impact parameter • Few nucleons participate • Few collisions • Smaller average number of collisions per participant • Small impact parameter • Many nucleons participate • Many, many collisions • Larger average number of collisions per participant • Common claim is that “harder” (“softer” ) processes scale with collisions (participants). Relative abundance of “harder” processes should rise with beam energy. • Centrality dependence should change with energy XLII Rencontres de Moriond La Thuile, Italy 24-Mar-2007 George S.F. Stephans

  11. Centrality dependence  II Energy and centrality dependencies factorize Effect of “harder” processes?? Phys.Rev. C74 (2006) 021901 arXiv:nucl-ex/0604017 XLII Rencontres de Moriond La Thuile, Italy 24-Mar-2007 George S.F. Stephans

  12. Centrality dependence  III Energy and centrality dependencies factorize even at pT~4 GeV/c Phys.Rev.Lett. 94 (2005) 082304 Nucl.Phys. A774 (2006) 113-128 XLII Rencontres de Moriond La Thuile, Italy 24-Mar-2007 George S.F. Stephans

  13. Centrality dependence  IV 200, 62.4 GeV Cu+Cu 200 GeV p+p, Cu+Cu & Au+Au Midrapidity ratio of anti-particles over particles (“chemistry”) at most weakly dependent on system size arXiv:nucl-ex/0701064 XLII Rencontres de Moriond La Thuile, Italy 24-Mar-2007 George S.F. Stephans

  14. Particle production in heavy ion collisions particle production energy, pseudorapidity, centrality, and pT Particle production summary Star formation in galaxies follows a quite simple pattern and simple patterns often mean that there are only [a] few basic physical mechanisms at work. ... We can now find out what these mechanisms are by measuring how star formation behaves with time and mass of the galaxy and compare that behavior to models. Kai Noeske UC Santa Cruz quoted in Science News 171, 121 (2007) XLII Rencontres de Moriond La Thuile, Italy 24-Mar-2007 George S.F. Stephans

  15. What’s next? • Fully incorporate all data, including p+p, d+Au, Cu+Cu & Au+Au (over expanded range of centrality) into the systematic studies • Continue expanding analysis into new area of fluctuations, including flow (last talk) and search for rare events of various types • Continue expanding analysis into new area of correlations, including both inclusive (next slide) and relative to a high pT trigger particle XLII Rencontres de Moriond La Thuile, Italy 24-Mar-2007 George S.F. Stephans

  16.        Cu+Cu Cu+Cu @ 200 GeV 0-10% central PHOBOS Preliminary h± p+p :clusters +6 -6 scale error 2 Clusters in particle production Define Keff = effective cluster size i.e. number of particles/cluster Particles produced in clusters of 2-3. Looking forward to doing systematics. arXiv:nucl-ex/0701055 XLII Rencontres de Moriond La Thuile, Italy 24-Mar-2007 George S.F. Stephans

  17. Conclusions • Many properties of single particle production in A+A @ RHIC energies are describable with a small number of surprisingly simple scalings • Range from very basic such as total multiplicity to more complicated features such as elliptic flow • Dependencies on incoming energy, pseudorapidity, centrality, & pT factorize to a surprising degree • Onward to more complicated observables • (And eventually to CMS@LHC!!) XLII Rencontres de Moriond La Thuile, Italy 24-Mar-2007 George S.F. Stephans

  18. Collaboration Burak Alver, Birger Back,Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Richard Bindel, Wit Busza (Spokesperson), Vasundhara Chetluru, Edmundo García, Tomasz Gburek, Joshua Hamblen, Conor Henderson, David Hofman, Richard Hollis, Roman Hołyński, Burt Holzman, Aneta Iordanova, Chia Ming Kuo, Wei Li, Willis Lin, Constantin Loizides, Steven Manly, Alice Mignerey, Gerrit van Nieuwenhuizen, Rachid Nouicer, Andrzej Olszewski, Robert Pak, Corey Reed, Christof Roland, Gunther Roland, Joe Sagerer, Peter Steinberg, George Stephans, Andrei Sukhanov, Marguerite Belt Tonjes, Adam Trzupek, Sergei Vaurynovich, Robin Verdier, Gábor Veres, Peter Walters, Edward Wenger, Frank Wolfs, Barbara Wosiek, Krzysztof Woźniak, Bolek Wysłouch 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 9 Current Ph.D. Students XLII Rencontres de Moriond La Thuile, Italy 24-Mar-2007 George S.F. Stephans

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