Limits on the Viscosity to Entropy Density Ratio from Production

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Transcript Limits on the Viscosity to Entropy Density Ratio from Production

07-Apr-08

Limits on the Viscosity to Entropy Density Ratio from PHENIX Data on Single Electron Production

24 W. A Zajc, for the PHENIX Collaboration Winter Workshop on Nuclear Dynamics

W.A. Zajc

07-Apr-08

Outline



Pre-History



History



Heavy Flavor Measurements



Estimating

/ s



Comparison to other estimates



Future directions

W.A. Zajc

07-Apr-08

Pre-History

I 

Fermi (1950)

 

“High Energy Nuclear Events”, Prog. Theor. Phys. 5, 570 (1950) Lays groundwork for statistical approach to particle production in strong interactions:



“Since the interactions of the pion field are strong, we may expect that rapidly this energy will be distributed among the various degrees of freedom present in this volume according to statistical laws.”

W.A. Zajc

07-Apr-08

Pre-History

II  

Landau (1955) significant extension of Fermi’s approach Considers fundamental roles of



hydrodynamic evolution



entropy



“The defects of Fermi’s theory arise mainly because the expansion of the compound system is not correctly taken into account… (The) expansion of the system can be considered on the basis of relativistic hydrodynamics.”

W.A. Zajc

07-Apr-08

Landau on Viscosity

1) Use of hydro relies on R/

>> 1 2) Negligible viscosity

equivalent to large Reynolds number

Re  r

VR/

>>1

VR/

~ V R / v th

so for relativistic system V ~ v th and

>>1



R /

>> 1 ; see #1

W.A. Zajc



Why

/s Matters

Any engineer will tell you



Kinematic viscosity

~ [Velocity] x [Length] is what matters (see Landau and remark on Reynolds number)



Any relativist will tell you

 r  e

+ p



Any thermodynamicist will tell you

 e

+ p = T s ( at

=0 )



 h

/

r  h

/

+ p

) 

(

/sT) = (

/s) (1/T)

07-Apr-08

~ (damping coefficient x thermal time)

W.A. Zajc

    

A Long Time Ago (1985)

Miklos Gyulassy and Pawel Danielewicz:



Dissipative Phenomena in Quark-Gluon Plasmas P. Danielewicz, M. Gyulassy Phys.Rev. D31, 53,1985. noted several restrictions on smallest allowed

: Most restrictive:

> h/

 h

> ~ n/3 But recall s = 3.6 n for the quanta they were considering

 h

/s > 1 / (3.6 x 3) ~ 1 / (4

) !!

07-Apr-08 W.A. Zajc

Perfect Fluids?

    07-Apr-08

First hydrodynamic calculations of the medium at RHIC assumed zero viscosity:

= 0, i.e. a “perfect fluid” Conjectured lower quantum limit



Derived first in (P. Kovtun, D.T. Son, A.O. Starinets, Phys.Rev.Lett.94:111601, 2005)



Motivated by AdS/CFT (Anti de Sitter space / Conformal Field Theory) correspondence (J. Maldacena: Adv. Theor. Math. Phys. 2, 231, 1998)

h 

“ordinary” fluids

 p 

water (at STP)

 h

/s ~ 380

p 

helium (at

point)

 h

/s ~ 9

“RHIC fluid”?

W.A. Zajc

    

Measuring

/s

Need observables that are sensitive to shear stress Damping (flow, fluctuations, heavy quark motion) ~

/s Flow

 

R. Lacey et al.: Phys. Rev. Lett. 98:092301, 2007



“Has the QCD critical point been signaled by observations at RHIC?” H.-J. Drescher et al.: Phys. Rev. C76:024905, 2007



“The Centrality Dependence of Elliptic Flow, the Hydrodynamic Limit, and the Viscosity of Hot QCD” Fluctuations



S. Gavin and M. Abdel-Aziz: Phys. Rev. Lett. 97:162302, 2006



“Measuring Shear Viscosity Using Transverse Momentum Correlations in Relativistic Nuclear Collisions” Heavy quark motion (drag, flow)



A. Adare et al. (PHENIX Collaboration): Phys. Rev. Lett. 98:092301, 2007



“Energy Loss and Flow of Heavy Quarks in Au+Au Collisions at √s NN = 200 GeV”

07-Apr-08 W.A. Zajc

Heavy-Flavor in PHENIX

K + Meson D ± (D 0 )

Mass 1.87 (1.87) GeV c c D 0 BR D 0 --> K

(3.85 ± 0.10) % BR D --> e +X 17.2 (6.7) %



BR D -->

+X 17.2 (6.6) % Near future



Reconstruction of hadronic decays K

  

D 0



Current measurements



indirect via semileptonic heavy-flavor decays



: 6 PRL, 1 PRC papers

  

talk: Y. Morino

m ±

: 1 PRC paper e + e : 1 PRL, 1 PLB submission



Upgrade: silicon vertex spectrometer

07-Apr-08 W.A. Zajc

Baseline: p+p at √s = 200 GeV



Heavy-flavor e

data



consistent with

FONLL

calculation:

ixed

rder

ext-to-

eading

og perturbative QCD

(M. Cacciari, P. Nason, R. Vogt PRL95,122001 (2005)) PRL 97, 252002 (2006)

 07-Apr-08

total cross section

 s

cc = 567

57(stat)

224(sys)

b talk: Y. Morino

W.A. Zajc

Au+Au at √s

=200 GeV: Spectra

PRL 98, 172301 (2007 )

R AA



N Yield binary in Au

 

Yield in Au p



PRL 98, 172301 (2007)

  07-Apr-08

Binary scaling of total e

± 

yield from heavy-flavor decays Expected from heavy-quark production via hard scattering High p T



suppression increasing with centrality Footprint of medium effects

W.A. Zajc



Nuclear Modification Factor R

AA R AA e

from heavy-flavor decays PRL 98, 172301 (2007) e ± from heavy flavor



Very similar to light hadron R AA



Careful:



decay kinematics!



p T (e

) < p T (D)



Intermediate p T



Indication for quark mass hierarchy as expected for radiative energy loss (Dokshitzer and Kharzeev, PLB 519(2001)199)



Highest p T



R AA (e

) ~ R AA (

0 ) ~ R AA (

)

 

Crucial to understand: what is the bottom contribution?

Ideal: R AA of identified charm and bottom hadrons

07-Apr-08 W.A. Zajc



e

R

: a Challenge for Models

Wicks et al., NPA 784(2007)426 Testing ground for various parton energy loss

)

models



Radiative

E only



Djordjevic et al., PLB 632(2006)81



Armesto et al., PLB 637(2006)362)



Collisional

E included

 

Wicks et al., NPA 784(2007)426 van Hees & Rapp, PRC 73(2006)034913)



Or alternative approaches to interpret the suppression



Collisional dissociation of heavy mesons (charm and bottom!)



Adil & Vitev, PLB 649(2007)139



Contribution from baryon enhancement



Sorensen & Dong, PRC 74(2006)024902 Adil & Vitev, PLB 649(2007)139

07-Apr-08 W.A. Zajc

 

Au+Au at √s

= 200 GeV: Flow(!)

Elliptic flow of e

± 

Non-zero v 2 from heavy-flavor decays (RHIC Run-4) minimum-bias PRELIMINARY PRL 98, 172301 (2007) Run-7 Rapp & van Hees, PRC 71, 034907 (2005)

   

Progress in Run-7

 

Improved reaction plane resolution (Increased statistics) Data are consistent within uncertainties Indication for non-zero v 2 at high p T (charm vs. bottom) Also available: v 2 vs. centrality Good agreement with Langevin based transport calculation including resonant elastic scattering

07-Apr-08 W.A. Zajc



Estimating

/s

Transport models



Rapp & van Hees (PRC 71, 034907 (2005))



Diffusion coefficient required for simultaneous fit of R AA and v 2



D HQ x2

T ~ 4-6



Moore & Teaney (PRC 71, 064904 (2005))

 

Difficulty describing R AA simultaneously and v 2 Calculate perturbatively (and argue that plausible also non-perturbatively)



D HQ / (

+P)) ~ 6 (for N f = 3)

07-Apr-08

PRL 98, 172301 (2007)

 

 e

= 0 + P = Ts then

 h

/s = (1.3-2.0)/4

p W.A. Zajc



Measuring

/s

Damping (flow, fluctuations, heavy quark motion) ~

 

FLOW: Has the QCD Critical Point Been Signaled by Observations at RHIC?, R. Lacey et al ., Phys.Rev.Lett.98:092301,2007 ( nucl-ex/0609025 ) The Centrality dependence of Elliptic flow, the Hydrodynamic Limit, and the Viscosity of Hot QCD , H.-J. Drescher et al ., ( arXiv:0704.3553

)

 ( 1 .

1  0 .

2  1 .

1  1 .

2 ) 1 4 p h

 ( 1 .

9  2 .

5 ) 1 4 p

C H A R M

 

FLUCTUATIONS: Measuring Shear Viscosity Using Transverse Momentum Correlations in Relativistic Nuclear Collisions , S. Gavin and M. Abdel-Aziz, Phys.Rev.Lett.97:162302,2006 ( nucl-th/0606061 ) DRAG, FLOW: Energy Loss and Flow of Heavy Quarks in Au+Au Collisions at √s NN = 200 GeV A. Adare et al ., (PHENIX Collaboration), to appear in Phys. Rev. Lett. ( nucl-ex/0611018 )

h s  ( 1 .

0  3 .

8 ) 1 4 p h s  ( 1 .

3  2 .

0 ) 1 4 p W.A. Zajc

 

Has the QCD Critical Point Been Signaled by Observations at RHIC?, R. Lacey et al ., Phys.Rev.Lett.98:092301,2007 ( nucl-ex/0609025 ) Signature: FLOW Calculation:

h On-shell transport model

for gluons

Z. Xu and

 165

c s

 3 MeV Fit v 2 ~I 1 (w)/I 0 (w); w = m T /2T C. Greiner, hep-ph/0406278.

c s

  0 .

35 0 .

3   0 .

05 0 .

03 fm 

Payoff Plot:

 h  1

( 1 .

1  0 .

2  1 .

1  1 .

2 ) 4 p PHENIX v 2 / e data (nucl-ex/0608033) compared to R.S. Bhalerao et al. (nucl-th/0508009) 07-Apr-08 W.A. Zajc

  

Measuring Shear Viscosity Using Transverse Momentum Correlations in Relativistic Nuclear Collisions , S. Gavin and M. Abdel-Aziz, Phys.Rev.Lett.97:162302,2006 ( nucl-th/0606061 ) Signature: FLUCTUATIONS Calculation:

 

 h

 2

Difference in correlation widths for central and peripheral s 2  s 0 2  4 h

  1

collisions s 

f c

, 2

 ~ s 1

2 fm  4 h

, 0      



P f

~     0  20 1 0

 

fm   Diffusion eq. for fluctuations

Compare to STAR data on centrality dependence of rapidity width s of p T fluctuations

Payoff Plot:

 h

 ( 1  3 .

8 ) 1 4 p 07-Apr-08 W.A. Zajc

  

The Centrality dependence of Elliptic flow, the Hydrodynamic Limit, and the Viscosity of Hot QCD , H.-J. Drescher et al ., ( arXiv:0704.3553

) Signature: FLOW Calculation:



l  rs

   1

 1

dN dy

  s (

c S

 )  s

A dN dy c S

Knudsen number K

Payoff Plot:

e 2 

e 2

perfect

  1 

1 /

0  

0   h

0 .

7  ,

c S

( 1 .

9  2 .

5 )  1/ 1 4 p 3 , h  1 .

264

/ s Decrease in flow due to finite size ,

 4

Fits to PHOBOS v2 data to determine s Glauber and for CGC initial conditions 07-Apr-08 W.A. Zajc

Comparison with other estimates

R. Lacey et al.: PRL 98:092301, 2007 H.-J. Drescher et al.: arXiv:0704.3553

S. Gavin and M. Abdel-Aziz: PRL 97:162302, 2006

h /

 ( 1 .

1  0 .

2  1 .

2 ) / 4 p

p T fluctuations STAR

h /

 ( 1 .

0  3 .

8 ) / 4 p

v 2 PHENIX & STAR v 2

h /

PHOBOS

 ( 1 .

4  2 .

4 ) / 4 p 

Estimates of

/s based on flow and fluctuation data



Indicate small value as well

 

Close to conjectured limit Significantly below

/s of helium (

4ph/

s ~ 9)

07-Apr-08

conjectured quantum limit

W.A. Zajc

Compare to the Competition

Strongly- Interacting Gas  

Damping of breathing mode in cold Fermi gas (All figures courtesy of John Thomas, Duke University)

3 He, 4 He near l point QGP simulations String-theory 1/4 p Schafer, cond-mat 2006 W.A. Zajc



Our Problem Is Much Harder

Non-relativistic: Damping given by



Relativistic: Causal, second-order expansion:



Relativistic Fluid Dynamics: Physics for Many Different Scales



Neglect various terms at your own risk:



Natsuume and Okamura, Comment on “Viscous hydrodynamics relaxation time from AdS/CFT correspondence”

07-Apr-08

talk: S. Pratt

W.A. Zajc

For Further Details



See “Virtual Journal on QCD Matter”

 

Steffen A. Bass, Berndt Mueller, William A. Zajc qgp.phy.duke.edu



On the topic of 2 nd order hydro:



What a Difference a Term Makes

07-Apr-08 W.A. Zajc

Viscosity Information from Relativistic Nuclear Collisions: How Perfect is the Fluid Observed at RHIC?, P. Romatschke and U. Romatschke, Phys. Rev. Lett. 99:172301, 2007

 

Signature: dN/dy, v 2 ,

Calculation: 2 nd order causal viscous hydro: (Glauber IC’s)

 

Payoff Plots:

 ( 0  2 .

0 ) 1 4 p 07-Apr-08 W.A. Zajc

Comparison with other estimates

R. Lacey et al.: PRL 98:092301, 2007 H.-J. Drescher et al.: arXiv:0704.3553

S. Gavin and M. Abdel-Aziz: PRL 97:162302, 2006

h /

 ( 1 .

1  0 .

2  1 .

2 ) / 4 p

p T fluctuations STAR

h /

 ( 1 .

0  3 .

8 ) / 4 p

v 2 PHENIX & STAR v 2

h /

PHOBOS

 ( 1 .

4  2 .

4 ) / 4 p

Romatschke 2 : PRL 99:172301, 2007



Estimates of

/s based on flow and fluctuation data



Indicate small value as well

 

Close to conjectured limit Significantly below

/s of helium (

4ph/

s ~ 9)

07-Apr-08

conjectured quantum limit

W.A. Zajc

 

Summary

Ongoing quantitative studies of sQGP properties



Heavy-flavor with m Q /T >> 1 a very valuable observable Consistent

/s estimates from single electron production, flow, and fluctuation data



“Near perfect” fluid at RHIC, with



~4 times smaller than

/s of helium (but at T ~ 10 12 K)



Close to the conjectured limit

/s =

..…..



Key for heavy-flavor physics in the future

 

Silicon vertex tracking Understanding D and B contributions

07-Apr-08 W.A. Zajc

07-Apr-08

The PHENIX Collaboration

Universidade de São Paulo, Instituto de Física, Caixa Postal 66318, São Paulo CEP05315-970, Brazil Institute of Physics, Academia Sinica, Taipei 11529, Taiwan China Institute of Atomic Energy (CIAE), Beijing, People's Republic of China Peking University, Beijing, People's Republic of China Charles University, Ovocnytrh 5, Praha 1, 116 36, Prague, Czech Republic Czech Technical University, Zikova 4, 166 36 Prague 6, Czech Republic Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic Helsinki Institute of Physics and University of Jyväskylä, P.O.Box 35, FI-40014 Jyväskylä, Finland Dapnia, CEA Saclay, F-91191, Gif-sur-Yvette, France Laboratoire Leprince-Ringuet, Ecole Polytechnique, CNRS-IN2P3, Route de Saclay, F-91128, Palaiseau, France Laboratoire de Physique Corpusculaire (LPC), Université Blaise Pascal, CNRS-IN2P3, Clermont-Fd, 63177 Aubiere Cedex, France IPN-Orsay, Universite Paris Sud, CNRS-IN2P3, BP1, F-91406, Orsay, France SUBATECH (Ecole des Mines de Nantes, CNRS-IN2P3, Université de Nantes) BP 20722 - 44307, Nantes, France Institut für Kernphysik, University of Münster, D-48149 Münster, Germany Debrecen University, H-4010 Debrecen, Egyetem tér 1, Hungary ELTE, Eötvös Loránd University, H - 1117 Budapest, Pázmány P. s. 1/A, Hungary KFKI Research Institute for Particle and Nuclear Physics of the Hungarian Academy of Sciences (MTA KFKI RMKI), H-1525 Budapest 114, POBox 49, Budapest, Hungary Department of Physics, Banaras Hindu University, Varanasi 221005, India Bhabha Atomic Research Centre, Bombay 400 085, India Weizmann Institute, Rehovot 76100, Israel Center for Nuclear Study, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan KEK, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan Kyoto University, Kyoto 606-8502, Japan Nagasaki Institute of Applied Science, Nagasaki-shi, Nagasaki 851-0193, Japan RIKEN, The Institute of Physical and Chemical Research, Wako, Saitama 351-0198, Japan Physics Department, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima, Tokyo 171-8501, Japan Department of Physics, Tokyo Institute of Technology, Oh-okayama, Meguro, Tokyo 152-8551, Japan Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305, Japan Waseda University, Advanced Research Institute for Science and Engineering, 17 Kikui-cho, Shinjuku-ku, Tokyo 162-0044, Japan Chonbuk National University, Jeonju, Korea Ewha Womans University, Seoul 120-750, Korea KAERI, Cyclotron Application Laboratory, Seoul, South Korea Kangnung National University, Kangnung 210-702, South Korea Korea University, Seoul, 136-701, Korea Myongji University, Yongin, Kyonggido 449-728, Korea System Electronics Laboratory, Seoul National University, Seoul, South Korea Yonsei University, IPAP, Seoul 120-749, Korea IHEP Protvino, State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, 142281, Russia Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia Russian Research Center "Kurchatov Institute", Moscow, Russia PNPI, Petersburg Nuclear Physics Institute, Gatchina, Leningrad region, 188300, Russia Saint Petersburg State Polytechnic University, St. Petersburg, Russia Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Vorob'evy Gory, Moscow 119992, Russia Department of Physics, Lund University, Box 118, SE-221 00 Lund, Sweden Abilene Christian University, Abilene, TX 79699, U.S.

Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY 11973-5000, U.S.

University of Colorado, Boulder, CO 80309, U.S.

Florida State University, Tallahassee, FL 32306, U.S.

Georgia State University, Atlanta, GA 30303, U.S.

Iowa State University, Ames, IA 50011, U.S.

14 Countries; 69 Institutions

Physics Department, Brookhaven National Laboratory, Upton, NY 11973-5000, U.S.

University of California - Riverside, Riverside, CA 92521, U.S.

Columbia University, New York, NY 10027 and Nevis Laboratories, Irvington, NY 10533, U.S.

Florida Institute of Technology, Melbourne, FL 32901, U.S.

University of Illinois at Urbana-Champaign, Urbana, IL 61801, U.S.

Lawrence Livermore National Laboratory, Livermore, CA 94550, U.S.

Los Alamos National Laboratory, Los Alamos, NM 87545, U.S.

University of Maryland, College Park, MD 20742, U.S.

Department of Physics, University of Massachusetts, Amherst, MA 01003-9337, U.S. Muhlenberg College, Allentown, PA 18104-5586, U.S.

University of New Mexico, Albuquerque, NM 87131, U.S. New Mexico State University, Las Cruces, NM 88003, U.S.

Oak Ridge National Laboratory, Oak Ridge, TN 37831, U.S.

RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, NY 11973-5000, U.S.

Chemistry Department, Stony Brook University, Stony Brook, SUNY, NY 11794-3400, U.S.

Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, NY 11794, U.S.

University of Tennessee, Knoxville, TN 37996, U.S.

Vanderbilt University, Nashville, TN 37235, U.S.

July 2007

W.A. Zajc

 

Viscosity Primer

Remove your organic prejudices



Don’t equate viscous with “sticky” !

Think instead of a not-quite-ideal fluid:

 

“not-quite-ideal”



Viscosity

then defined as “supports a shear stress”

F A x

  h 



y x



Dimensional estimate:

η   (

momentum n p mfp



n density

)  (

mean p

n

σ 

p

free path

) 

small viscosity



Large

cross sections



Large



Strong

cross sections



couplings



strong

couplings perturbation theory

fails

07-Apr-08 W.A. Zajc

 

The (Assumed) Connection

Exploit

Maldacena’s “D-dimensional strongly coupled gauge theory stringy gravity”



Thermalize

with massive black brane (D+1)-dimensional h

m   

Calculate

viscosity

= “Area”/16

Normalize

by entropy (density) s = “Area” / 4G

Dividing out

the infinite “areas” : A



Infinite “Area” !

  (

) 1 4 p

m  

Conjectured

to be a lower bound “ for all relativistic quantum field theories at finite temperature and zero chemical potential ”.

See

“ Viscosity in strongly interacting quantum field theories from black hole physics ”, P. Kovtun, D.T. Son, A.O. Starinets, Phys.Rev.Lett.94:111601, 2005, hep-th/0405231

07-Apr-08 W.A. Zajc



The Primacy of QCD

While the (conjectured) bound

h  

4 p

is a purely quantum mechanical result . . .

 

It was derived in and motivated by the Anti-de Sitter space / Conformal Field Theory correspondence Weak form:



“Four-dimensional

=4 supersymmetric SU(N c ) gauge theory is equivalent to IIB string theory with AdS 5 x S 5 boundary conditions.” ( The Large N limit of superconformal field theories and supergravity , J. Maldacena, Adv. Theor. Math. Phys. 2, 231, 1998 hep-th/9711200 )



Strong form:



“Hidden within ( every non-Abelian gauge theory, even within the weak and strong nuclear interactions, is a theory of quantum gravity.” Gauge/gravity duality , G.T. Horowitz and J. Polchinski, gr-qc/0602037 )



Strongest form: fascinating connections over the full range of the coupling constant to study QGP



Only with QCD can we explore

Quantum Gauge Phluid

experimentally these

07-Apr-08 W.A. Zajc

Energy Loss and Flow of Heavy Quarks in Au+Au Collisions at √s (PHENIX Collaboration), A. Adare NN = 200 GeV et al ., Phys. Rev. Lett. 98:172301,2007 ( nucl ex/0611018 )

 

Signature: FLOW, ENERGY LOSS Calculation:

D HQ

~ ( 4  6 ) 2 p

Rapp and van Hees Phys.Rev.C71:034

D HQ

/ ( h /( e 

) ) ~ 6 907,2005, to fit

both

PHENIX v 2 (e) and R AA (e)  h

 ( 1 .

3  2 .

0 ) 1 4 p for

N f

 3 Moore and Teaney Phys.Rev.C71:064 904,2005 (perturbative, argue ~valid non-perturbatively) 

Payoff Plot:

07-Apr-08 W.A. Zajc

07-Apr-08

A Victim of the Missing Term?



Entropy production in high-energy heavy-ion collisions and the correlation of shear viscosity and thermalization time, A. Dumitru

et al

., Phys. Rev. C76:024910, 2007 .

W.A. Zajc

(Some) Things I’d Like To Know



Are there better ways to extract

/s ?

 

Can these existing estimates be improved ?

(In particular, can systematic errors be understood?)



All of these methods rely on

+P = Ts .



How does this change in the presence of a conserved charge ?



In ordinary fluids,

/s has a pronounced minimum near the critical point.



Can AdS/CFT say

anything

about this for gauge fluids?

07-Apr-08 W.A. Zajc



(More) Things I’d Like To Know

What does flow scaling tell us about degrees of freedom?



Hadronic Modes and Quark Properties in the Quark-Gluon Plasma, M. Mannarelli and R. Rapp, arXiv:hep-ph/0505080v2 : m ~ 150 MeV ,

~ 200 MeV .



Is any form of quasiparticle consistent with KSS bound?

 

All(?) AdS/CFT calculations find drag ~ √

= √g 2 N C . What is this telling us about the degrees of freedom ?



Is there a unique prescription for fixing coupling ?



Is there well-controlled expansion away from ‘t Hooft limit?



Calibrate it with lattice ‘data’ ?



ASIDE: Those who most often pronounce “AdS/CFT is useless because the coupling doesn’t run” are those most likely to do calculations with

s = 0.5 .

07-Apr-08 W.A. Zajc

(More) Things I’d Like To Know



Are AdS/CFT predictions falsifiable ?



What if Song and Heinz

/s < 1/4

p 

is correct?

Suppression of elliptic flow in a minimally viscous quark-gluon plasma, H. Song and U. Heinz, arXiv:0709.0742v1

 

What if Mach cone angles different from data ?

What if 1/√

not seen in J/

suppression ?

 

What data can best constrain initial conditions?

(Will we ever be able to eliminate this source of ambiguity between Glauber, CGC, … ?)



Are there AdS/CFT setups to do elliptic flow dynamically?



Can they say anything about the observed scaling ?

07-Apr-08 W.A. Zajc

(Big ) Things I’d Like To Know



Can one start from confining, chiral Sakai-Sugimoto and push it through a phase transition ?



Hod tells us



> 1 /



Universal Bound on Dynamical Relaxation Times and Black-Hole Quasinormal Ringing , S. Hod, arXiv:gr-qc/0611004v1



Can AdS/CFT address this ?



What does it mean to have a gravity dual ?



In particular, how do I find it ?



What is the impact of the KSS conjecture on other fields ?

07-Apr-08 W.A. Zajc



Perfect

The “fine structure” v hydrodynamics 2 (p T ) for different mass particles shows good agreement with ideal (“perfect fluid”)

KE T



2 

p T

2  07-Apr-08

Roughly: ∂



m



Work-energy theorem

  

P d(vol) =

E K



m T – m 0

 D

KE T

W.A. Zajc



The “Flow” Knows Quarks

The “fine structure” v hydrodynamics 2 (p T ) for different mass particles shows good agreement with ideal (“perfect fluid”) baryons mesons



Scaling flow parameters by quark content n q resolves meson-baryon separation of final state hadrons

07-Apr-08 W.A. Zajc