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Roy A. Lacey

Roy A. Lacey. Is the quark gluon plasma strongly or weakly coupled?. What Motivates the Search for the Critical end point (CEP)?. M. A. Stephanov, K. Rajagopal and E. V. Shuryak, Phys. Rev. Lett. 81 (1998) 4816; Phys. Rev. D 60 (1999) 114028.

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Roy A. Lacey

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  1. Roy A. Lacey Is the quark gluon plasma strongly or weakly coupled? Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  2. What Motivates the Search for the Critical end point (CEP)? M. A. Stephanov, K. Rajagopal and E. V. Shuryak, Phys. Rev. Lett. 81 (1998) 4816; Phys. Rev. D 60 (1999) 114028 Discovery of the crossover transition from the Quark Gluon Plasma to hadronic matter Aoki et al • Flow Measurements • Space-time measurements • Jet Quenching Hot QCD Collab The Crossover is a necessary requirement for existence the CEP Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  3. t t = -z/c t = z/c eBjorken~ 5 - 15 GeV/fm3 ~ 35 – 100 ε0 0 z:collision axis Gold nucleus Gold nucleus v~0.99c Hadronization ? “Thermalized” partonic Fluid! (s)QGP? A “little Bang” occurs in RHIC collisions Challenge: Establish Constraints to address these question Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  4. u Truth, Myth or Propaganda ? The QGP is strongly Coupled! Yes! E. V. Shuryak, Nucl. Phys. A750, 64 (2005) η/s is very small Yes! U. Heinz and P. Kolb, Nucl. Phys. A702, 269 (2002) The related question as to the degree of local Equilibrium achieved is also unsettled? The question of whether or not the QGP produced in heavy ion collisions is strongly coupled is crucial & unsettled ! Perhaps Not! M. Asakawa et. al, Phys. Rev. Lett. 96, 252301 (2006). η/s size, not sufficient No! N. Borghini and J.-Y. Ollitrault, Phys. Lett. B642, 227 65 (2006), Truth, Myth or Propaganda ? The degree of local Equilibrium is known! Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  5. u How do we address the strength of the coupling and the degree of thermalization? Prerequisite: First Rate Flow Data The extraction of a small value of η/s linked to a short mean free path λ, would lend decisive insight Viscous hydro Transport Several Hybrids of Hydro and Transport First rate differential flow data is an asset! Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  6. Why Flow Measurements? Control Params. From ET Distributions Expect Large Pressure Gradients  Hydro Flow Deviations of Elliptic & hexadecapole flow from ideal hydrodynamic expectations -> Constraints for thermalization, sound speed, viscosity, etc. Detailed integral and differential Measurements now available What do they tell us ? Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  7. Central Arms Recent Measurements New RXN detector RXN RXN BBC/MPC BBC/MPC PHENIX Preliminary Event planes Five separate measurements of v2 and v4 in the same experiment is decisive Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  8. Baryons Mesons Phys. Rev. Lett. 98, 162301 (2007) KET – CQN Scaling It is often argued that Strong coupling is Incompatible with quark degrees of freedom This argument against quark degrees of freedom is therefore ill-informed! Quark-Like Degrees of Freedom Evident Indication of strong coupling? Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  9. CQN & KET Scaling for OZI suppressed particle species & Heavy quarks v2 for the D follows that of other mesons v2 for the φ follows that of other mesons A Phase with Quark-like dynamical degrees of freedom Dominates the flow – hadronic contributions not significant Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  10. Is there value added for v4Measurements? Recombination Predicted Signal for hydrodynamic behavior -> local equilibrium Ollitrault et al Quark recombination models predict specific relationship between the ratio v4/(v2)2 for hadrons and partons Scaling relation between Baryons and Mesons Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  11. KET and CQN Scaling for v4 PHENIX Preliminary KET & nq2 scaling validated for v4 Further Indication of strong coupling? Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  12. v4/(v2)2 ratio for different particle species V4 = k(v2)2 where k is the same for different particle species Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  13. Flow is universal PHENIX Preliminary V4 = k(v2)2 where k is the same for different particle species. Demonstrates the universal nature of vn Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  14. Is this an indication that the partonic fluid is thermalized? α Related to η/s ? • Lessons • Hardoniaztion? • 2. Partonic Thermalization? Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  15. u Can we estimate the strength of the coupling and the degree of thermalization ? Prerequisite: First Rate Flow Data The extraction of a small value of η/s linked to a short mean free path λ, would lend decisive insight Viscous hydro Transport Several Hybrids of Hydro and Transport We now consider one hybrid approach Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  16. Hybrid Approach Operational Ansatz (Ollitrault) The Boltzmann equation reduces to hydrodynamics when the mean free path is small C. Marle, Annales Poincare Phys.Theor. 10,67 (1969). System characterized by two Dimensionless numbers The liquidity or dilution number (D) The Knudsen number (Kn) Applicability of Boltzmann D << 1 Hydrodynamics is the limit Kn << 1 One can then use transport to study and parameterize the approach to hydrodynamic behavior (local equilibrium) Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  17. Hybrid Approach Degree of local equilibrium Schematic calculation For a given value of D Functional form does not depend on D Determined from fit to calculations This provides a simple fitting ansatz for the data and Straightforward procedure for local equilibrium estimate “Any untaken shot is 100% missed ” Wayne Gretzky Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  18. An Operational Test Use procedure to study simulated data Operational ansatz validated Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  19. Truth or Myth – Good fits to the data PHENIX Preliminary Within model ansatz straightforward to extract degree of local equilibrium! 10-15% larger than for fluid with η/s =1/4π in central events. Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  20. Truth or Myth – Good fits to the data PHENIX Preliminary Hydro like Npart dependence for v4 Similar Conclusions Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  21. Summary of v2 and v4 PHENIX Preliminary λ = 0.3 – 0.35 Straightforward estimation of the degree of local equilibrium and η/s as a function of centrality! 10-15% larger than for fluid with η/s =1/4π in central events. Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  22. Data Fits PHENIX Preliminary Fits allow η/s estimate as function of centrality etc. λ = 0.3 – 0.35 Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  23. Heavy Quark Constraint PRL 98, 172301 (2007) nucl-ex/0610029 Heavy quarks provide a compatible constraint? Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  24. Coefficients from Transport C. Greiner et al Thermalization facilitated by 23 processes Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  25. The Matter is Dense and Quenches Jets An estimate of the density Estimates indicate sizeable density Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  26. Transport Coefficient Estimates Lacey & Taranenko nucl-ex/0610029 2 X the conjectured lower bound Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  27. Danielewicz, Lacey, Lynch New Constraints for the Hadronic EOS? EOS not very well constrained experimentally Further constraints for the hadronic EOS Soft and hard EOS Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  28. Epilogue • Flow measurements tell us that the hot QCD matter created at RHIC is a strongly coupled plasma: • flows as a (nearly) perfect fluid with systematic patterns consistent with quark degrees of freedom. • has a soft EOS and a viscosity to entropy density ratio close to the conjectured quantum bound. • η/s decreases as collisions become more central • The mean free path (λ) in central collisions is short ~ 0.3 - 0.35 Will be interesting to see what other approaches have to say -- The ball is now in the Theorists court!! Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  29. KET/n scaling across collision centralities KET/n scaling observed across centralities Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  30. The Charm of D meson flow Heavy quark relaxation time Moore & Teaney Equilibration rate Diffusion Coefficient V2 of charm quark can provide invaluable access to the diffusion coefficient (D) Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  31. Overall Scaling of Elliptic Flow at RHIC Particles flow with common velocity field Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  32. Prologue: The Rich Structure of the Integral Flow Excitation Function The transition from in-plane to out-of-plane and back to in-plane emission Is understood Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  33. Low Energy: Squeeze-out DATA (KAOS – Z. Phys. A355(1996); (E895) - PRL 83(1999) 1295 Prologue: Passing-time scaling of squeeze-out Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  34. Danielewicz, Lacey, Lynch Good Constraints for the EOS achieved Soft and hard EOS Prologue: Constraints for the Hadronic EOS Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  35. The Charm of D meson flow The D meson not only flows, it scales over the measured range Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  36. u There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns. There are things we don't know we don't know Donald Rumsfeld Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

  37. End Roy A. Lacey, Symposium on the Physics of Dense Baryonic Matter , GSI March 9-10, 2009

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