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The strongly Interacting Quark Gluon Plasma (sQGP) a perspective from the PHENIX collaboration

the “other” big experiment

Richard SetoWhitten Memorial Symposium

UCLADec 13, 2011

First few Slides based on talks from 20th anniversary celebration: Shoji, BillPrimarily heavy ion results

Picture ofWhitten

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Some history: A tale of 3• The three:• DIMUON

• muons, hadrons

• TALES-SPARC• Low mass dielectrons• photons

• OASIS• High pT particles• Electrons• photons

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And then there was one- 1991

05-Dec-11

• A three way marriage (shotgun wedding)– RE2

• “RHIC Experiment 2”

“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.”

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 4

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=== 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.Grosse Perdekamp, 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.Grosse Perdekamp (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-Officio2006-2009) D. Morrison (2009-2011; then Ex-Officio; also2003-2006) 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-...)

Did the marriage work?e.g. Executive Council members since 1994

TALES-SPARCDIMUONOASIS“Newcomers”

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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

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First Data (2001)“A Look at Jet Quenching?”

RAA0

0

in AuAu collisions in pp collisions

ColorlessHadrons

ColoredQGP

colored quarks from hard scattering

Caution optimism” data seemed consistent

with jet quenching

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Early data: d+Au (2003)

• A worry: cold nuclear matter effects could be causing suppression

• Answer: d+Au collisions showed no suppression

d+Au

Au+Au

RdA

π0

Another worry: is the binary scaling correct?

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Recent Data• Photons

– binary scaling OK

• Heavy quarks also suppressed

π0

Direct γ

Heavy Quarks

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Flow: How explosive is the sQGP?2 2

2 2 2 cos 2x y

x y

p pv

p p

dn/d ~ 1 + 2 v2(pT) cos (2 ) + ...

x

yz

Coordinate space: initial asymmetry

pressure

py

px

Momentum space: final asymmetry

pre-RHIC prejudice - weakly interacting QGP weak flow signal

Strong flow Signal

PHENIXHuovinen et al

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)

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I Guess flow is important

after all

v2

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

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A period of assessment: Cautious optimism

• 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

do I believe this? Time to Evaluate

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

~1000 citations but that is what it is: the sQGP

Black body “thermal” photons Temperature from the data

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pQCD

Energy

Inte

nsity Thermal

photons

• Make a measure of low pT photons

• Do a fit to models• Ti~300-600 MeV

depending on Model• Greater than TC!

– TC ~170 MeV (from lattice)

• IT’S HOT ENOUGH !05-Dec-11

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“gauge-gravity duality” – aka string theory: an interesting connection

• Hydrodynamic models require small η/s (viscosity) to reproduce flow signal

• Small viscosity Strongly interactingCan we calculate the viscosity ()?BIG problem, QCD in our regime is a strongly coupled theoryPerturbative 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 connection05-Dec-11

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Calculating the viscosity (from Feynman)

energy momentum stress tensor

Bigger F/A larger viscosityLarger viscosity smaller v0 Larger viscosity can act over larger d

y

x

Einstein field eqn

Possibility to solve a strongly coupled theory! (for the first time??)

String theory: Extra Dimensions

“QCD” strong couplingComplicated

4d Boundary(we live here)

5d bulk theory z

dual

Black hole“Simple”

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An Analogy What is this??

In 3D – Its easy to see

Its a Hologram

Chessmen – a knight, bishop, king, pawn

Hmm... lets think. Its in 2D You’re kidding!

dual

using gauge-string duality (AdS/CFT)

σ(0)=area of black hole horizon

dual Gravity=4 SYM“QCD”strong coupling

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14 4 Bs k

This is believed to be a universal lower bound for a wide class ofGauge theories with a gravity dual

Heavy quarks◦ Strong suppression◦ Flow

Fits(via the heavy quark diffusion coefficient) yield

η/s ~ (1-2)/4π Strongly Interacting

Throw a rock in a stream: Heavy quarks – η/s from the data

PRL 98, 172301 (2007)21

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V3

V2

𝜂𝑠=

14𝜋

𝜂𝑠=

24𝜋

Recently v3η/s

V2 measurement consistentWith η/s= 1/4π or 2/4πDepending on assumedInitial conditions

V3 measurement breaksThis ambiguityη/s= 1/4π

Unprecedented capability to make quantitative measurementsPossibility to ask detailed questions about a QCD system

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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?

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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

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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

3005-Dec-11

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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?