versus AdSCFT Perils Pitfalls Progress Prospects WA Zajc Physics Department Columbia University New York NY this talk available at http wwwphenixbnlgovphenixWWWpublishzajcsppresentationsDurham ID: 815549
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Slide1
Durham WorkshopHeavy Ion Physics“versus” AdS/CFTPerils, Pitfalls, Progress, ProspectsW.A. ZajcPhysics Department Columbia University, New York, NY ( this talk available at http://www.phenix.bnl.gov/phenix/WWW/publish/zajc/sp/presentations/Durham )
16-Apr-09
W.A. Zajc
Slide2AdS/CFT - ProGauge/gravity duality, G.T. Horowitz and J. Polchinski, gr-qc/0602037 )“Hidden within every non-Abelian gauge theory, even within the weak and strong nuclear interactions, is a theory of quantum gravity.”Stringscape, by Matthew Chalmers, in Particle World:“Susskind says that by studying heavy-ion collisions you are also studying quantum gravity that is ‘blown up and slowed down by a factor of 1020 ’ ”The Black Hole War, L. Susskind, ISBN 978-0-316-01640-7 :“…the Holographic Principle is evolving from radical paradigm shift to everyday working tool of – surprisingly – nuclear physics.” 16-Apr-09W.A. Zajc
Slide3AdS/CFT - ConP. Petreczsky, QM09: “AdS/CFT is consistently wrong. ”16-Apr-09W.A. Zajc
Slide4HypothesisReality may lie between these two extremes For discussion:Hard physicsFragile predictionsRobust extractionsSoft physics: Robust predictionsFragile extractionsNot covered:AdS/QCD16-Apr-09W.A. Zajc
Slide5What Worked?: Quantitative pQCDSystematic Comparison of Jet Energy-Loss Schemes in a Realistic Hydrodynamic Medium, S.A. Bass et al., 0808.0908A (valuable!) exercise in Procrustean reductionism.Good news:“Bad” news:16-Apr-09
W.A. Zajc
Slide6CommentYes- to some extent this is an illustration of the “fragility” of RAA More differential more sensitiveIAA RAA versus reaction planeHowever- not the real issue (see B. Cole QM08)Instead: consistent treatment of collisional + radiative terms, finite L, expanding medium, coupling constant, kinematic cut-offs, assumed scale hierarchies, …16-Apr-09W.A. Zajc
Slide7Strings That Might WorkAdS/CFT is a general correspondenceMost useful to QCD whenHow to equate QCD N =4 SYM ?Naïve?Correct for different d.o.f. ?Equal energy densities ?Equivalent q-q potential ?16-Apr-09W.A. Zajc
Slide819-Nov-08Michigan ColloquiumNew Dimensions in Heavy Ion PhysicsOur 4-d worldString theorist’s 5+5-d world
The stuff formerly known as QGP
Heavy quark moving through the medium
Energy loss from string drag
Jet modifications from wake field
“
The stress tensor of a quark moving through
N
=4
thermal plasma
”, J.J. Friess
et al
.,
hep-th
/0607022
Slide9Heavy Quark Energy Loss in AdS/CFT(Infinitely) massive quark trailing stringGeneral agreement on exact parametric form:Heavy quark diffusion in strongly coupled N = 4 Yang Mills, Casalderrey-Solana and Teaney, hep-ph/0605199 Energy loss of a heavy quark moving through N = 4 supersymmetric Yang-Mills plasma, Herzog et al., hep-th/0605158.Drag force in AdS/CFT, Gubser, hep-th/0605182Roughly consistent with observed single-electron suppression pattern:Heavy
Quark Diffusion with Relativistic Langevin
Dynamics in the Quark-Gluon
Fluid,
Akamatsu
, Hatsuda and Hirano,
0809.1499
(next slide)
16-Apr-09
W.A. Zajc
Slide10Heavy Quark Drag vs Data16-Apr-09W.A. ZajcAdS/CFT g ~ 2-3 within uncertainty band:Heavy Quark Diffusion with Relativistic Langevin Dynamics in the Quark-Gluon Fluid, Akamatsu, Hatsuda and Hirano, 0809.1499
Slide11Light Quark Energy Loss in AdS/CFT (1)Not yet (AFAIK) embedded in realistic hydro code no direct comparison !Lightlike Wilson loop formalism(Liu, Rajagopal, Wiedemann http://arxiv.org/abs/hep-ph/0605178 )Find for l = 6p aS = 0.5Energy loss not proportional to number d.o.f (!)16-Apr-09
W.A. Zajc
Slide12Light Quark Energy Loss in AdS/CFT (2)But- completely different results in alternative set-ups:Falling stringLight quark energy loss in strongly-coupled N = 4 supersymmetric Yang-Mills plasma, Chesler et al., 0810.1985Gluon energy loss in the gauge-string duality, Gubser et al., 0803.1470Parton branching in N=4Jet evolution in the N=4 SYM plasma at strong coupling, Hatta, Iancu and Mueller, 0803.2481Each have regimes corresponding to very high values of “quenching parameter “ ~10-100 GeV
2/fm
See talk by E.
Iancu
for much more detail
16-Apr-09
W.A. Zajc
Slide13Q. What Worked ?A. Ideal hydro: (Liu, Hirano, Werner, Zhu; QM09) 16-Apr-09W.A. Zajc
Slide14AssertionIn these complicated events, we have (a posteriori) control over the event geometry:Degree of overlapOrientation with respect to overlap
Reaction
Plane
“
Central
”
“
Peripheral
”
Slide15Implications of AssertionWe have (a posteriori) control over the event geometry:Two possible scenarios:
“Free” quarks and gluons
“Strongly-coupled” quarks and gluons
Slide1619-Nov-08Michigan ColloquiumMotion Is Hydrodynamic
x
y
z
When does thermalization occur?
Strong evidence that
final state
bulk behavior
reflects the
initial state
geometry
Because the initial
azimuthal asymmetry
persists in the final state
dn
/
d
f
~ 1 + 2
v
2
(
p
T
)
cos
(2
f
) + ...
Slide17(Minimal) AdS / CFT 16-Apr-09
Graviton with
5-momentum
k
in bulk satisfies
k
k
= 0
described by
4
numbers
Those
4
numbers describe virtual gauge quanta on
4-d
boundary
( Adopted from
S. Brodsky figure
)
W.A. Zajc
Slide1816-Apr-09A Long Time Ago (1985)Dissipative Phenomena in Quark-Gluon Plasmas, P. Danielewicz and M. Gyulassy, Phys.Rev. D31, 53,1985. Noted several restrictions on smallest allowed h : Most restrictive: l > h/<p>
h
> ~ n / 3
But recall
s = 3.6 n
for the
quanta they were considering
h
/s > 1 / (3.6 x 3) ~ 1 / (4
p
)
!!
W.A. Zajc
Slide1923-Oct-08W.A. ZajcEstimating h/s Damping (flow, fluctuations, heavy quark motion) ~ h/sHas 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
)
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
)
Energy
Loss and Flow of
Heavy Quarks in Au+Au Collisions
at √
s
NN
= 200 GeV
(PHENIX Collaboration),
A. Adare
et al
.,
to appear in Phys. Rev. Lett. (
nucl
-ex/0611018
)
C
H
A
R
M
!
Slide2023-Oct-08W.A. ZajcMeasuring 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: FLUCTUATIONSCalculation:Payoff Plot:
Diffusion eq. for fluctuations g
Compare
to STAR data on centrality dependence of rapidity width
s
of
p
T
fluctuations
Difference
in correlation widths for central and peripheral collisions
Slide2123-Oct-08W.A. ZajcHas the QCD Critical Point Been Signaled by Observations at RHIC?, R. Lacey et al., Phys.Rev.Lett.98:092301,2007 (nucl-ex/0609025)Signature: FLOWCalculation:Payoff Plot:
Fit v
2
~I
1
(w)/I
0
(w); w =
m
T
/2T
On-shell transport model for gluons
,
Z. Xu and C. Greiner,
hep
-ph/0406278
.
PHENIX
v
2
/
e
data (
nucl
-ex/0608033) compared to R.S.
Bhalerao
et al.
(
nucl-th
/0508009)
Slide2223-Oct-08W.A. ZajcThe Centrality dependence of Elliptic flow, the Hydrodynamic Limit, and the Viscosity of Hot QCD, H.-J. Drescher et al., (arXiv:0704.3553)Signature: FLOWCalculation:Payoff Plot:
Knudsen
number K
Fits
to PHOBOS v2 data to determine
s
for Glauber and CGC initial conditions
Decrease
in flow due to finite size
Slide2323-Oct-08W.A. Zajc Moore and Teaney Phys.Rev.C71:064904,2005 (perturbative, argue ~valid non-perturbatively)Energy Loss and Flow of Heavy Quarks in Au+Au Collisions at √sNN = 200 GeV (PHENIX Collaboration), A. Adare et al., Phys. Rev. Lett. 98:172301,2007 (nucl
-ex/0611018)
Signature
:
FLOW, ENERGY LOSS
Calculation:
Payoff
Plot:
Rapp
and van
Hees
Phys.Rev.C71:034907,2005, to fit
both
PHENIX v
2
(e) and R
AA
(e)
Slide24Non-Ideal Hydrodynamics Simple in 1st order, but… :Unknown Initial ConditionsEccentricity fluctuationsUnknown equation of stateInstabilities, acausal effects in relativistic viscous hydroHadronic rescattering effectsBulk viscosityNumerical viscosityFinite size, core/corona effects
16-Apr-09
W.A. Zajc
Slide25Implementing and TestingExamplesP. Romatschke and U. Romatschke, Phys. Rev. Lett. 99:172301, 2007H. Song and U. Heinz, Phys. Rev. C78, 024902, 2008
M.
Luzum
and
P
. Romatschke hys.Rev.C78:034915,2008
.
16-Apr-09
1 fm/c
3 fm/c
7 fm/c
W.A. Zajc
Slide26BNL, April 2008:Workshop on Viscous Hydrodynamics and Transport Models in Heavy Ion CollisionsWorkshop SummaryConcordance 16-Apr-09
M.
Luzum
and P.
Romtschke
Phys.Rev.C78:034915,2008
.
W.A. Zajc
Slide2716-Apr-09S. Gavin and M. Abdel-Aziz: PRL 97:162302, 2006
p
T
fluctuations
STAR
Comparison of Estimates
R. Lacey et al.: PRL 98:092301, 2007
v
2
PHENIX
& STAR
H.-J.
Drescher
et al.: arXiv
:
0704.3553
v
2
PHOBOS
conjectured quantum limit
Various 2
nd
order
hydro calculations
A. Adare
et al
, PRL 98:172301, 2007
Heavy flavor
drag, flow;
PHENIX
W.A. Zajc
Slide28W.A. ZajcBeyond ‘t Hooft Limit ? (1)A foolish consistency is the hobgoblin of little minds…Hydro direct photon results (Liu, Hirano, Werner, Zhu; QM09) use
Slide29W.A. ZajcBeyond ‘t Hooft Limit ? (2)Use this range for aS ~0.25-0.33 in result from Myers, Paulos and Sinha (http://arxiv.org/abs/0806.2156)(Using most naïve as= gYM2/4
p )
Compare this to
compilation of
h
/s estimates:
!
Slide30W.A. ZajcBeyond ‘t Hooft Limit ? (3)
Consistency check: Use
same
range
a
S
~0.25-0.33
In ‘ancient’ result from
Gubser, Klebanov and
Tseytlin
(
http://arxiv.org/abs/hep-th/9805156
)
(Using
most naïve
a
s
= g
YM
2
/4
p
)
Check if this corresponds
to ‘sensible’ temperature
range using lattice results
for s(T)/s
SB
:
Slide31PreliminaryKnowing Knudsen Experimental fit of Knudsen number K = lmfp/R on way to
h/s estimate:
16-Apr-09
Still to do- Understand systematics !
Assumed T
Assumed
s
Boltzmann transport
W.A. Zajc
Slide3216-Apr-09S. Gavin and M. Abdel-Aziz: PRL 97:162302, 2006
p
T
fluctuations
STAR
Comparison of Estimates
R. Lacey et al.: PRL 98:092301, 2007
v
2
PHENIX
& STAR
H.-J.
Drescher
et al.: arXiv
:
0704.3553
v
2
PHOBOS
conjectured quantum limit
Various 2
nd
order
hydro calculations
A. Adare
et al
, PRL 98:172301, 2007
Heavy flavor
drag, flow;
PHENIX
W.A. Zajc
Slide33Why I Think Knudsen Kneeds Work…Because you Kneed Kneither s nor cS:Starting point is always de Groot result:Then assumed finite-size scaling Directly gives you K l , resulting in This is (AFAIK) the sole physical content of this “formalism”, and you would probably “tune” it with hydro anyway…16-Apr-09W.A. Zajc
Slide34What About LQCD ?Transport coefficients are challenging:Nf=2+1 on 16 x 483 lattice estimated at O(10) days on Exaflop machine(!) H. Meyer, QM09Nonetheless:16-Apr-09W.A. Zajc
Slide35Perspective16-Apr-09W.A. ZajcKeep in mind the neglected:Bulk viscosity(=0 in CFT)Hadronic viscosity(potentially large )( compilation from Aihong Tang, QM09)
Slide36W.A. ZajcBeyond ‘t Hooft Limit ? (Caveats)The range for aS is very sensitive to the value for h/s : (Using most naïve as= gYM2/4p )
Compare this to compilation (
Aihong Tang
, QM09)
of
h
/s estimates:
Slide37The Flow Knows QuarksThe “fine structure” v2(pT) for different mass particles shows good agreement with ideal (“perfect fluid”) hydrodynamicsScaling
flow parameters by quark content
n
q
resolves
meson-baryon separation of final state hadrons
baryons
mesons
Slide38RecombinationRecombination works: Deal with itMiklos Gyulassy: “One of the most remarkable ‘I don’t understand’ phenomena”16-Apr-09W.A. Zajc
Slide39Implications for D.O.FWhile tempting to identify the coalescence patterns with “underlying quark degrees of freedom”…Much work still needed to reconcile with ‘absence’ of quasiparticles when h/s near quantum boundQuasi-Particle Degrees of Freedom versus the Perfect Fluid as Descriptors of the Quark-Gluon Plasma, L.A. Levy et al., Phys.Rev.C78:044905,2008. 0709.3105 Quantum Criticality and Black Holes, S. Sachdev and M. Mueller, 0810.3005 :“The theory of the quantum critical region shows that the transport coefficients, and the relaxation time to local equilibrium, are not proportional to a mean free scattering time between excitations, as is the case in the Boltzmann theory of quasiparticles16-Apr-09W.A. Zajc
Slide4009-Mar-09Harvard ColloquiumWhy AdS/CFT Matters…All the thermal parts are built upon Bekenstein and Hawking’s (unproven) assertion that black holes have entropy:Black holes have a temperature
Black holes can radiate
Black holes don’t lose information
Important to test these very underpinnings
Slide41Calculating Multiplicity = EntropyOff-center collisions in AdS5 with applications to multiplicity estimates in heavy-ion collisions, Gubser, Pufu and Yarom ( 0902.4062 )FAILS !But- AdS/CFT can’t separate “participants” from “spectators”, so…Fix this by hand (restrict E in shock by fractional overlap)16-Apr-09W.A. Zajc
Slide42A ‘Better” Adjustment16-Apr-09W.A. ZajcMake AdS/CFT more QCD-like by restricting 5th dimension zIR > z > zUV :Pro: More ‘realistic’ predictions for LHCCon: Breaks again…
Slide43SummaryAdS/CFT has produced qualitatively new insights into the dynamics of heavy ion collisions.The hard sector is hard.The soft sector is “firm”. Much ongoing activity to turn qualitative insights into quantitative results.16-Apr-09W.A. Zajc
Slide44Thank you !16-Apr-09W.A. Zajc
Slide45The Charm PuzzleConserved !Loses energy: PHENIX and STARRAA ~ consistentRAA ~ unchangedin region whereb’s should dominateFlowsAgain, little evidence fordecoupling of b’s16-Apr-09
W.A. Zajc
Slide46Ongoing Work on QP’sHadronic modes and quark properties in the quark-gluon plasma, M. Mannarelli and R. Rapp,hep-ph/0505080 Quasi-particle model for lattice QCD: Quark-gluon plasma in heavy ion collisions, V. Chandra and V. Ravishankar, 0812.1430Parton transport and hadronization from the dynamical quasiparticle point of view, W. Cassing and E.L. Bratkovskaya,
0808.0022
The Hot non-perturbative gluon plasma is an almost ideal colored liquid, A.
Peshier
and W.
Cassing
,
hep
-ph/0502138
16-Apr-09
W.A. Zajc
Slide47Beyond h/s = 1/4p, A. Buchel, R.C. Meyers and A. Sinha, 0812.252116-Apr-09W.A. Zajc
Slide48Speaking of CartoonsWhat is this thing ??Surely not the space-time development:W.A. Zajc
?
16-Apr-09
Slide49Restating the “Obvious”A reminder:All nuclei are finiteMost nuclei are roundNo nuclei areInfiniteCylindricalSharp spheres….16-Apr-09W.A. Zajc
Slide50Lesson16-Apr-09W.A. ZajcDetails matter.