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Durham Workshop Heavy Ion Physics “versus” AdS/CFT Perils, Pitfalls, Progress, Prospects

Durham Workshop Heavy Ion Physics “versus” AdS/CFT Perils, Pitfalls, Progress, Prospects W.A. Zajc Physics Department Columbia University, New York, NY ( this talk available at http:// www.phenix.bnl.gov/phenix/WWW/publish/zajc/sp/presentations/Durham ). AdS/CFT - Pro.

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Durham Workshop Heavy Ion Physics “versus” AdS/CFT Perils, Pitfalls, Progress, Prospects

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  1. Durham Workshop Heavy Ion Physics“versus” AdS/CFTPerils, Pitfalls, Progress, Prospects W.A. ZajcPhysics Department Columbia University, New York, NY ( this talk available at http://www.phenix.bnl.gov/phenix/WWW/publish/zajc/sp/presentations/Durham) W.A. Zajc

  2. AdS/CFT - Pro • Gauge/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.” W.A. Zajc

  3. AdS/CFT - Con P. Petreczsky, QM09: “AdS/CFT is consistently wrong. ” W.A. Zajc

  4. Hypothesis • Reality may lie between these two extremes  • For discussion: • Hard physics • Fragile predictions • Robust extractions • Soft physics: • Robust predictions • Fragile extractions • Not covered: • AdS/QCD W.A. Zajc

  5. What Worked?: Quantitative pQCD Systematic Comparison of Jet Energy-Loss Schemes in a Realistic Hydrodynamic Medium, S.A. Bass et al., 0808.0908 A (valuable!) exercise in Procrustean reductionism. Good news: “Bad” news: W.A. Zajc

  6. Comment • Yes- to some extent this is an illustration of the “fragility” of RAA • More differential  more sensitive • IAA • RAA versus reaction plane • However- 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, … W.A. Zajc

  7. Strings That Might Work • AdS/CFT is a general correspondence • Most useful to QCD when • How to equate QCD  N =4 SYM ? • Naïve? • Correct for different d.o.f. ? • Equal energy densities ? • Equivalent q-q potential ? W.A. Zajc

  8. New Dimensions in Heavy Ion Physics • “The stress tensor of a quark moving through N=4 thermal plasma”, J.J. Friess et al., hep-th/0607022 Our 4-d world The stuff formerly known as QGP Jet modifications from wake field Heavy quark moving through the medium String theorist’s 5+5-d world Energy loss from string drag Michigan Colloquium

  9. Heavy Quark Energy Loss in AdS/CFT • (Infinitely) massive quark  trailing string • General 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/0605182 • Roughly consistent with observed single-electron suppression pattern: • Heavy Quark Diffusion with Relativistic LangevinDynamics in the Quark-Gluon Fluid, Akamatsu, Hatsuda and Hirano, 0809.1499(next slide) W.A. Zajc

  10. Heavy Quark Drag vs Data W.A. Zajc • AdS/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

  11. Light 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 = 0.5 • Energy loss not proportional to number d.o.f (!) W.A. Zajc

  12. Light Quark Energy Loss in AdS/CFT (2) • But- completely different results in alternative set-ups: • Falling string • Light quark energy loss in strongly-coupled N = 4 supersymmetric Yang-Mills plasma, Chesler et al., 0810.1985 • Gluon energy loss in the gauge-string duality, Gubser et al., 0803.1470 • Parton branching in N=4 • Jet evolution in the N=4 SYM plasma at strong coupling, Hatta, Iancu and Mueller, 0803.2481 • Each have regimes corresponding to very high values of “quenching parameter“ ~10-100 GeV2/fm • See talk by E. Iancu for much more detail W.A. Zajc

  13. Q. What Worked ? A. Ideal hydro: (Liu, Hirano, Werner, Zhu; QM09) W.A. Zajc

  14. Assertion ReactionPlane • In these complicated events, we have (a posteriori) control over the event geometry: • Degree of overlap • Orientation with respect to overlap “Central” “Peripheral”

  15. Implications of Assertion • We have (a posteriori) control over the event geometry: • Two possible scenarios: “Free” quarks and gluons “Strongly-coupled” quarks and gluons

  16. Motion Is Hydrodynamic z y x • When does thermalization occur? • Strong evidence that final state bulk behavior reflects the initial state geometry • Because the initial azimuthal asymmetrypersists in the final statedn/df ~ 1 + 2v2(pT) cos (2 f) + ... Michigan Colloquium

  17. (Minimal) AdS / CFT Graviton with 5-momentum k in bulk satisfies kk = 0  described by 4numbers Those 4 numbers describe virtual gauge quanta on 4-d boundary ( Adopted from S. Brodsky figure ) W.A. Zajc

  18. A 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

  19. Estimating h/s • Damping (flow, fluctuations, heavy quark motion) ~ h/s • 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. Drescheret 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 √sNN = 200 GeV (PHENIX Collaboration), A. Adare et al., to appear in Phys. Rev. Lett. (nucl-ex/0611018) CHARM! W.A. Zajc

  20. 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) Diffusion eq. for fluctuations g • Signature: FLUCTUATIONS • Calculation: • Payoff Plot: Compare to STAR data on centrality dependence of rapidity width s of pT fluctuations Difference in correlation widths for central and peripheral collisions W.A. Zajc

  21. Has the QCD Critical Point Been Signaled by Observations at RHIC?,R. Lacey et al., Phys.Rev.Lett.98:092301,2007 (nucl-ex/0609025) Fit v2 ~I1(w)/I0(w); w = mT/2T • Signature: FLOW • Calculation: • Payoff Plot: On-shell transport model for gluons, Z. Xu and C. Greiner, hep-ph/0406278. PHENIX v2/edata (nucl-ex/0608033) compared to R.S. Bhalerao et al. (nucl-th/0508009) W.A. Zajc

  22. The Centrality dependence of Elliptic flow, the Hydrodynamic Limit, and the Viscosity of Hot QCD, H.-J. Drescheret al., (arXiv:0704.3553) • Signature: FLOW • Calculation: • Payoff Plot: Knudsen number K Decrease in flow due to finite size Fits to PHOBOS v2 data to determine s for Glauber and CGC initial conditions W.A. Zajc

  23. 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) Moore and Teaney Phys.Rev.C71:064904,2005 (perturbative, argue ~valid non-perturbatively) • Signature: FLOW, ENERGY LOSS • Calculation: • Payoff Plot: Rapp and van Hees Phys.Rev.C71:034907,2005, to fit both PHENIX v2(e) and RAA(e) W.A. Zajc

  24. Non-Ideal Hydrodynamics • Simple in 1st order, but… : • Unknown Initial Conditions • Eccentricity fluctuations • Unknown equation of state • Instabilities, acausal effects in relativistic viscous hydro • Hadronic rescattering effects • Bulk viscosity • Numerical viscosity • Finite size, core/corona effects W.A. Zajc

  25. Implementing and Testing 7 fm/c 3 fm/c 1 fm/c • Examples • P. Romatschke and U. Romatschke,Phys. Rev. Lett. 99:172301, 2007 • H. Song and U. Heinz, Phys. Rev. C78, 024902, 2008 • M. Luzum and P. Romatschke hys.Rev.C78:034915,2008. W.A. Zajc

  26. Concordance M. Luzum and P. Romtschke Phys.Rev.C78:034915,2008.  • BNL, April 2008: • Workshop on Viscous Hydrodynamics and Transport Models in Heavy Ion Collisions • Workshop Summary W.A. Zajc

  27. Comparison of Estimates H.-J. Drescher et al.: arXiv:0704.3553 v2 PHOBOS Various 2nd orderhydro calculations conjectured quantum limit S. Gavin and M. Abdel-Aziz: PRL 97:162302, 2006 R. Lacey et al.: PRL 98:092301, 2007 pTfluctuations STAR v2 PHENIX & STAR A. Adare et al, PRL 98:172301, 2007 Heavy flavor drag, flow; PHENIX W.A. Zajc

  28. Beyond ‘t Hooft Limit ? (1) • A foolish consistency is the hobgoblin of little minds… • Hydro direct photon results (Liu, Hirano, Werner, Zhu; QM09) use W.A. Zajc

  29. Beyond ‘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= gYM2/4p ) • Compare this to compilation of h/s estimates: ! W.A. Zajc

  30. Beyond ‘t Hooft Limit ? (3) • Consistency check: Use same range aS ~0.25-0.33 In ‘ancient’ result from Gubser, Klebanov and Tseytlin (http://arxiv.org/abs/hep-th/9805156) • (Using most naïve as= gYM2/4p ) • Check if this correspondsto ‘sensible’ temperaturerange using lattice resultsfor s(T)/sSB :  W.A. Zajc

  31. Knowing Knudsen Preliminary • Still to do- Understand systematics ! • Assumed T • Assumed s • Boltzmann transport Experimental fit of Knudsen number K = lmfp/R on way to h/s estimate: W.A. Zajc

  32. Comparison of Estimates H.-J. Drescher et al.: arXiv:0704.3553 v2 PHOBOS conjectured quantum limit S. Gavin and M. Abdel-Aziz: PRL 97:162302, 2006 R. Lacey et al.: PRL 98:092301, 2007 pTfluctuations STAR v2 PHENIX & STAR Various 2nd orderhydro calculations A. Adare et al, PRL 98:172301, 2007 Heavy flavor drag, flow; PHENIX W.A. Zajc

  33. Why I Think Knudsen Kneeds Work… • Because you Kneed Kneithers 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… W.A. Zajc

  34. What About LQCD ? Transport coefficients are challenging: Nf=2+1 on 16 x 483 lattice estimated at O(10) days on Exaflop machine(!) H. Meyer, QM09 Nonetheless: W.A. Zajc

  35. Perspective (compilationfrom Aihong Tang, QM09) W.A. Zajc • Keep in mind the neglected: • Bulk viscosity(=0 in CFT) • Hadronic viscosity(potentially large )

  36. Beyond ‘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: W.A. Zajc

  37. The Flow Knows Quarks • The “fine structure” v2(pT) for different mass particles shows good agreement with ideal (“perfect fluid”) hydrodynamics • Scaling flow parameters by quark content nqresolves meson-baryon separation of final state hadrons baryons mesons

  38. Recombination • Recombination works: • Deal with it • Miklos Gyulassy: “One of the most remarkable ‘I don’t understand’ phenomena” W.A. Zajc

  39. Implications for D.O.F • While 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 bound • Quasi-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 quasiparticles W.A. Zajc

  40. Why 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 Harvard Colloquium

  41. Calculating Multiplicity = Entropy • Off-center collisions in AdS5with 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) W.A. Zajc

  42. A ‘Better” Adjustment W.A. Zajc • Make AdS/CFT more QCD-like by restricting 5th dimension zIR> z > zUV : • Pro: More ‘realistic’ predictions for LHC • Con: Breaks again…

  43. Summary AdS/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 insightsinto quantitative results. W.A. Zajc

  44. Thank you ! W.A. Zajc

  45. The Charm Puzzle • Conserved ! • Loses energy: • PHENIX and STARRAA ~ consistent • RAA ~ unchangedin region whereb’s should dominate • Flows • Again, little evidence fordecoupling of b’s W.A. Zajc

  46. Ongoing Work on QP’s Hadronic 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, 0812.1430 Parton 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 W.A. Zajc

  47. Beyond h/s = 1/4p, A. Buchel, R.C. Meyers and A. Sinha,0812.2521 W.A. Zajc

  48. Speaking of Cartoons ? What is this thing ?? Surely not the space-time development: W.A. Zajc

  49. Restating the “Obvious” • A reminder: • All nuclei are finite • Most nuclei are round • No nuclei are • Infinite • Cylindrical • Sharp spheres • …. W.A. Zajc

  50. Lesson Details matter. W.A. Zajc

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