Richard Seto Whitten Memorial Symposium UCLA Dec 13, 2011

1. The strongly Interacting Quark Gluon Plasma (sQGP) a perspective from the PHENIX collaborationthe “other” big experiment Richard Seto Whitten Memorial Symposium UCLA Dec 13, 2011 Picture of Whitten First few Slides based on talks from 20th anniversary celebration: Shoji, Bill Primarily heavy ion results

2. Some history: A tale of 3 • The three: • DIMUON • muons, hadrons • TALES-SPARC • Low mass dielectrons • photons • OASIS • High pT particles • Electrons • photons

3. And then there was one- 1991 “reject all three Letters of Intent because of what were felt to be major deficiencies in each of them.” “The Committee decided to place the emphasis on a detector designed to measure electrons and photons emerging from the QGP.” “Those of you who are primarily interested in hadron physics will be welcomed by the STAR Collaboration which has been empowered to build a large TPC detector.” • A three way marriage (shotgun wedding) • RE2 • “RHIC Experiment 2”

4. PHENIX rising: Pioneering High Energy Nuclear Interaction Experiment:electrons, muons, photons, hadrons • Two Central Arms • Electrons, Photons, Hadrons • Two Muon Arms • Spin program • Major funding from outside sources – e.g Japan

5. Did the marriage work?e.g. Executive Council members since 1994 === Membership of PHENIX Executive Council (since 1994) ==== ************************************************************ Ex-Officio members: B.V. Jacak, Spokesperson (12/2006-...) Akiba, Deputy Spokesperson (2004-...) D. Morrison, Deputy Spokesperson (2011-...) J. Nagle, Deputy Spokesperson (2009-...) E. O'Brien, Operations Director (2002-...) ---------------- current above this line --------------- M.GrossePerdekamp, Deputy Spokesperson (2004-2009) R. Seto, Deputy Spokesperson (12/2006-2009) A. Drees, Upgrades Manager (2002-2008) W.A. Zajc, Spokesperson (1997-2006; appointed 2007-...) G.R. Young, Deputy Spokesperson (1994-2003) J. Haggerty, Deputy Project Director (1998-2001) M. Marx, Deputy Project Director (1996-2001) L. Paffrath, Project Engineer (1994-1998) S. Nagamiya, Spokesperson (1994-1997) ************************************************************ Elected members: A. Frawley (1/2005-1/2014) G. David (1/2011-1/2014) M. Leitch (1/2007-1/2013) J. Lajoie (1/2007-1/2013) M.GrossePerdekamp (1/2010-1/2013; Ex-Officio 1/2004-1/2009) Y. Goto (1/2009-1/2012) C. Aidala (1/2011-1/2012) ---------------- current above this line --------------- A. Deshpande (2005-1/2011) J. Nagle (2009-2012, but became Ex-Officio in 2009) T. Hemmick (1999-2009) N. Saito (2004-2009) V. Cianciolo (2004-2007) R. Seto (1997-2006; then Ex-Officio 2006-2009) D. Morrison (2009-2011; then Ex-Officio; also 2003-2006) H. En'yo (1997-2004) M. Tannenbaum (1994-2004) B. Jacak (1994-2005; Spokesperson 12/2006-...) J. Haggerty (1997-1998; then Deputy Project Director) W. A. Zajc (1994-1997; Spokesperson 1997-2006; appointed 2007-...) S. White (1997-2000) H.-A. Gustafsson (1997-2000) H. Hamagaki (1997-2000) F. Plasil (1996-1999) R. Hayano (1994-1997) K. Imai (1994-1997) W. Kinnison (1994-2000) J. Thomas (1994-1997) *************************************************** Appointed by the Spokesperson: O. Drapier (1/2007-...) R. Seto, (5/2010-...) W.A. Zajc (1/2007-...) ---------------- current above this line ---------- M. Gonin (2004-2007?) S.V. Greene (2004-2007?) N. Saito (2001-2004) I. Tserruya (2001-2004) ***************************************************************** Secretary: B. Johnson (1994-...) TALES-SPARC DIMUON OASIS “Newcomers”

6. Pre-History • Unusual effects in heavy ions at the AGS/CERN • Hadronic explanations (e.g. Cold nuclear matter effects) • Lack of clarity  heightened sense of caution • Flow skepticism • We had no idea what we would see – even the basic things like multiplicity were unknown • We were hoping to see a weakly Interacting QGP • Note: the first eagerly awaited multiplicity results were on the low side (remember?) –I was a bit depressed BUT

7. First Data (2001)“A Look at Jet Quenching?” colored quarks from hard scattering Colorless Hadrons Caution optimism” data seemed consistent with jet quenching Colored QGP RAA

8. Early data: d+Au (2003) • A worry: cold nuclear matter effects could be causing suppression • Answer:d+Au collisions showed no suppression RdA d+Au π0 Au+Au Another worry: is the binary scaling correct?

9. Recent Data • Photons • binary scaling OK • Heavy quarks also suppressed Direct γ Heavy Quarks π0

10. py px z y x  Flow: How explosive is the sQGP? pressure Coordinate space: initial asymmetry Momentum space: final asymmetry • dn/d ~ 1 + 2v2(pT)cos (2 ) + ... • pre-RHIC prejudice - weakly interacting QGP •  weak flow signal

11. PHENIX Huovinen et al Strong flow Signal I Guess flow is important after all • Implications • Strongly interacting • Early thermalization • detailed hydro calculations (QGP+mixed+RG, zero viscosity) • 0 ~ 0.6 -1.0 fm/c • ~15-25GeV/fm3 • (ref: cold matter 0.16 GeV/fm3) v2

12. A few other results: • Transverse energy and multiplicity • ε ~ 5-15 GeV/fm3. • Particle Yields • chemical equilibrium • Large Baryon/meson ratio as a function of pT • Quark recombination

13. A period of assessment: Cautious optimism do I believe this? Time to Evaluate • Talk Titles • “A Look at Jet Quenching?” • The First 3 Years at RHIC an Overview and (careful) Assessment • The First 4 Years at RHICA Critical Assessment

14. The PHENIX Whitepaper (2005) • Title: Formation of dense partonic matter in relativistic nucleus–nucleus collisions at RHIC: Experimental evaluation by the PHENIX Collaboration • The Conclusion “This state of matter is not describable in terms of ordinary color-neutral hadrons, because there is no known self-consistent theory of matter composed of ordinary hadrons at the measured densities. The most economical description is in terms of the underlying quark and gluon degrees of freedom.” • Interesting fact (to me) – we never use the words strongly interacting Quark Gluon Plasma but that is what it is: the sQGP ~1000 citations

15. Black body “thermal” photons Temperature from the data • Make a measure of low pTphotons • Do a fit to models • Ti~300-600 MeV depending on Model • Greater than TC! • TC ~170 MeV (from lattice) • IT’S HOT ENOUGH ! Thermal photons Intensity pQCD Energy

16. “gauge-gravity duality” – aka string theory: an interesting connection • Hydrodynamic models require small η/s (viscosity) to reproduce flow signal • Small viscosity  Strongly interacting Can we calculate the viscosity ()? BIG problem, QCD in our regime is a strongly coupled theory Perturbative techniques do NOT work To the rescue! String theory !? Sociological notes on PHENIX collaborators: Lots of puzzlement during this time about viscosity Strong interesting in the string theory connection

17. Calculating the viscosity (from Feynman) y Bigger F/A  larger viscosity Larger viscosity smaller v0 Larger viscosity can act over larger d x energy momentum stress tensor Einstein field eqn

18. String theory: Extra Dimensions “QCD” strong coupling Complicated 4d Boundary (we live here) dual 5d bulk theory z Black hole “Simple” Possibility to solve a strongly coupled theory! (for the first time??)

19. An Analogy What is this?? Chessmen – a knight, bishop, king, pawn You’re kidding! Hmm... lets think. Its in 2D dual In 3D – Its easy to see Its a Hologram

20. using gauge-string duality (AdS/CFT) =4 SYM “QCD” strong coupling Gravity dual σ(0)=area of black hole horizon This is believed to be a universal lower bound for a wide class of Gauge theories with a gravity dual

21. PRL 98, 172301 (2007) Throw a rock in a stream: Heavy quarks – η/s from the data • Heavy quarks • Strong suppression • Flow • Fits(via the heavy quark diffusion coefficient) yield η/s ~ (1-2)/4π Strongly Interacting

22. Recently v3η/s V2 measurement consistent With η/s= 1/4π or 2/4π Depending on assumed Initial conditions V2 V3 measurement breaks This ambiguity η/s= 1/4π V3 Unprecedented capability to make quantitative measurements Possibility to ask detailed questions about a QCD system

23. Questions: • Are quarks strongly coupled to the quark-gluon plasma at all interaction distance scales? • What are the detailed mechanisms for parton-QGP interactions and responses? Are the interactions coherent over the entire medium length scale, what are the dominant energy loss mechanisms? • Are there quasi-particles in the medium? What are their masses and widths? • Is there a relevant color screening length in the quark-gluon plasma? • How is rapid equilibration and entropy production achieved? • What is the nature of color charge in large nuclei? What role does gluon saturation and the EMC effect play in nucleus-nucleus collisions? How do these modifications evolve?

24. The future: sPHENIX – a jet detector • Is RHIC relevant in the LHC era? • YES ! • QCD Condensed matter physics • Jets become our “laser” with which to probe the medium • sPHENIX – a jet detector: 20-60 GeV

29. Conclusion • There is little doubt that we are creating a strongly interacting Quark Gluon Plasma at RHIC • We are starting to make quantitative measurement with unprecedented accuracy, unthinkable when RHIC began • LHC experiments are reinforcing this conclusion and adding new information and techniques • Next task – quantifying the sQGP • Studying the “condensed matter” of QCD

31. Questions: • Are quarks strongly coupled to the quark-gluon plasma at all interaction distance scales? • What are the detailed mechanisms for parton-QGP interactions and responses? Are the interactions coherent over the entire medium length scale, what are the dominant energy loss mechanisms? • Are there quasi-particles in the medium? What are their masses and widths? • Is there a relevant color screening length in the quark-gluon plasma? • How is rapid equilibration and entropy production achieved? • What is the nature of color charge in large nuclei? What role does gluon saturation and the EMC effect play in nucleus-nucleus collisions? How do these modifications evolve?