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Outline: Motivation. Interest and observables Available data and scaling

Beam energy dependence of the viscous damping of anisotropic flow in relativistic heavy ion collisions Roy A. Lacey Stony Brook University. Outline: Motivation. Interest and observables Available data and scaling Demonstration of scaling in visc . hydro Results Conclusion.

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Outline: Motivation. Interest and observables Available data and scaling

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  1. Beam energy dependence of the viscous damping of anisotropic flow in relativistic heavy ion collisions Roy A. Lacey Stony Brook University • Outline: • Motivation. • Interest and observables • Available data and scaling • Demonstration of scaling in visc. hydro • Results • Conclusion We now have strong indications for a change in the dynamics with √ Roy A. Lacey, Stony Brook University, QM2014

  2. p Quantitative study of the QCD phase diagram is a central current focus of our field Conjectured Phase Diagram • A Known known • Spectacular achievement: • Validation of the crossover • transition leading to the QGP  Necessary requirement for CEP • Known unknowns • Location of the critical End point (CEP)? • Location of phase coexistence regions? • Detailed properties of each phase? • All are fundamental to the phase diagram of any substance Measurements which span a broad range of the ()-plane are essential for detailed studies of the phase diagram Roy A. Lacey, Stony Brook University, QM2014

  3. A Current Strategy Exploit the RHIC-LHC beam energy lever arm (,T) at freeze-out Energy scan M. Malek, CIPANP (2012) J. Cleymans et al. Phys. Rev. C73, 034905 • LHC  access to high T and small • RHICaccess to different systems and • a broad domain of the (,T)-plane • LHC + BES  access to an even broader domain of the (,T)-plane RHICBES to LHC  360 increase Challenge  identification of robust signals Roy A. Lacey, Stony Brook University, QM2014

  4. Lacey et. al, Phys. Rev.Lett. 98 (2007) 092301 arXiv:0708.3512(2008) Possible signals Csernai et. al, Phys.Rev.Lett. 97 (2006) 152303 A. Dobado et. al, Phys. Rev. D 79, 014002 (2009) H2O Argon At the CEP or close to it, anomalies in the dynamic properties of the medium can drive abrupt changes in transport coefficients Anisotropic flow (vn) measurements are an invaluable probe Roy A. Lacey, Stony Brook University, QM2014

  5. Possible signals Collapse of directed flow H. Stoecker, NPA 750, 121 (2005) Dirk Rischke and MiklosGyulassy Nucl.Phys.A608:479-512,1996 Dirk Rischkeand MiklosGyulassy Nucl.Phys.A608:479-512,1996 In the vicinity of a phase transition or the CEP, the sound speed is expected to soften considerably. In the vicinity of a phase transition or the CEP anomalies in the space-time dynamics can enhance the time-like component of emissions. v1 and HBT measurements are invaluable probes Roy A. Lacey, Stony Brook University, QM2014

  6. Anisotropic flow Measurements Lacey et. al, Phys.Rev.Lett. 112 (2014) 082302 CMS - Phys.Rev.C87, 014902 (2013) STAR - Phys.Rev.C86, 014904 (2012); Phys.Rev.C86, 054908 (2012) • An extensive set of flow measurements now span a broad range of beam energies (). Roy A. Lacey, Stony Brook University, QM2014

  7. STAR - 1403.4972 HBT Measurements ALICE -PoSWPCF2011 For detailed presentations of PHENIX data See talks by: Ron Soltz Tue. 15:00 - 15:20 HeliumDarmstadtium NuggehalliAjitanand Wed. 12:30 - 12:50 EuropiumDarmstadtium Exquisite data set for combined RHIC-LHC results? Roy A. Lacey, Stony Brook University, QM2014

  8. Acoustic Scaling Essential Questions Can the wealth of data be understood in a consistent framework? • If it can, what new insight/s are we afforded? • Do we see evidence for the CEP? YES! Expansion dynamics is pressure driven and is therefore acoustic! • This acoustic property leads to several testable scaling predictions for anisotropic flow and HBT Staig & Shuryak arXiv:1008.3139 Lacey et. al, arXiv:1301.0165 scaling for the HBT radii scaling for anisotropic flow These scaling properties are evidenced by viscous hydrodynamics Roy A. Lacey, Stony Brook University, QM2014

  9. Geometric quantities for scaling Geometry Phys. Rev. C 81, 061901(R) (2010) B A arXiv:1203.3605 σx & σy RMS widths of density distribution • Geometric fluctuations included • Geometric quantities constrained by multiplicity density. Roy A. Lacey, Stony Brook University, QM2014

  10. scaling of anisotropic flow - Viscous Hydrodynamics • Characteristic a • η/s Roy A. Lacey, Stony Brook University, QM2014

  11. Scaling properties of flow Acoustic Scaling of shape-engineered events • Characteristic viscous damping validated • for different event shapes at the same centrality • A strong constraint for initial-state models and η/s • 4πη/s for RHIC plasma ~ 1 • 4πη/s for LHC plasma ~ 2 Following calibration Roy A. Lacey, Stony Brook University, QM2014

  12. Scaling properties of flow Acoustic Scaling – Lacey et. al, Phys.Rev.Lett. 112 (2014) 082302 200 GeV 7.7 GeV 19.6 GeV 39 GeV 62.4 GeV 2.76 TeV • Characteristic viscous damping validated across beam energies • First experimental indication for η/s variation in the -plane • CEP? HBT should show complimentary signals for similar Roy A. Lacey, Stony Brook University, QM2014

  13. Scaling properties of HBT Viscous Hydrodynamics – B. Schenke • Characteristic a Freeze-out time varies with initial size Freeze-out transverse size proportional to initial transverse size Roy A. Lacey, Stony Brook University, QM2014

  14. Acoustic Scaling of HBT Radii • and mT scaling of the full RHIC and LHC data sets • The centrality and mT dependent data scale to a • single curve for each radii. • Qualitatively similar expansion dynamics at RHIC & LHC Roy A. Lacey, Stony Brook University, QM2014

  15. Acoustic Scaling of HBT Radii Femtoscopic measurements arXiv:1404.5291 NuggehalliAjitanand Wed. 12:30 - 12:50 EuropiumDarmstadtium • Larger expansion • rate at the LHC • exquisitely demonstrated via HBT measurement for several systems Roy A. Lacey, Stony Brook University, QM2014

  16. dependence of HBT signals Ron Soltz Tue. 15:00 - 15:20 HeliumDarmstadtium These characteristic patterns signal an important change in the reaction dynamics CEP? Phase transition? Roy A. Lacey, Stony Brook University, QM2014

  17. Lacey et. al, Phys.Rev.Lett. 112 (2014) 082302 dependence of HBT signals STAR Combined results  Strongest indications for the CEP to date! Roy A. Lacey, Stony Brook University, QM2014

  18. Epilogue Acoustic scaling of anisotropic flow and HBT radii lend profound mechanistic insights, as well as new constraints for key observables What do we learn? • The expansion dynamics is acoustic – “as it should be” • Validates expected acoustic scaling of flow and HBT radii • constraints for 4πη/s & viable initial-state models • 4πη/s for RHIC plasma ~ 1~ my 2006 estimate • 4πη/s for LHC plasma ~ 2 • Extraction insensitive to initial geometry model • Characteristic dependence of • viscous coefficient β” on • give new constraints which could be an indication for reaction trajectories in close proximity to the CEP? Roy A. Lacey, Stony Brook University, QM2014

  19. End Roy A. Lacey, Stony Brook University, QM2014

  20. Directed flow of transported protons H. Stoecker, NPA 750, 121 (2005) Data qualitatively resembles predictions of a hydrodynamic model with a first-order phase transition Roy A. Lacey, Stony Brook University, QM2014

  21. HBT Observables proxy for the sound speed estimate for initial size in central events Study HBT observables as a function of Roy A. Lacey, Stony Brook University, QM2014

  22. Extraction of η/s Slope sensitive to 4η/s Characteristic viscous damping validated in viscous hydrodynamics;calibration  4πη/s ~ Extracted η/s value insensitive to initial conditions Roy A. Lacey, Stony Brook University, QM2014

  23. Extraction of η/s arXiv:1301.0165 & CMS PAS HIN-12-011 Viscous Hydro Slope sensitive to η/s n2 scaling validated in experiment and viscous hydrodynamics; calibration  4πη/s ~ 2 Note agreement with Schenke et al. Roy A. Lacey, Stony Brook University, QM2014

  24. Improved Methodology BjoernSchenke et. al. arXiv:1301.5893 4πη/s for LHC plasma ~ 2 Higher harmonics provide important constraints! Can we find methodologies and constraints which are insensitive to the initial-state geometry? Roy A. Lacey, Stony Brook University, QM2014

  25. Scaling properties of flow Initial Geometry characterized by many shape harmonics (εn)  drive vn Acoustic viscous modulation of vn Staig & ShuryakarXiv:1008.3139 Scaling expectations: n2 dependence vn is related to v2 System size dependence Each of these scaling expectations can been validated η/s , ’ Roy A. Lacey, Stony Brook University, QM2014

  26. Scaling properties of flow Acoustic Scaling – Centrality 5-70% • Eccentricity change alone is not sufficient • To account for the Npart dependence of vn • Transverse size () influences viscous damping • Characteristic scaling prediction is • non-trivial Roy A. Lacey, Stony Brook University, QM2014

  27. Scaling properties of flow Acoustic Scaling – • Characteristic viscous damping validated • at RHIC & the LHC • A further constraint for η/s Roy A. Lacey, Stony Brook University, QM2014

  28. Shape-engineered events Shape fluctuations lead to a distribution of the Q vector at a fixed centrality • Cuts on qn should change the magnitudes ,, at a given centrality due to fluctuations • These magnitudes can influence scaling • Note characteristic anti-correlation predicted for v3(q2) in mid-central events • Crucial constraint for initial-geometry models Roy A. Lacey, Stony Brook University, QM2014

  29. Shape-engineered events ALICE data Shape fluctuations lead to a distribution of the Q vector at a fixed centrality q2(Hi) • Cuts on qn should change the magnitudes ,, at a given centrality due to fluctuations q2(Lo) • Viable models for initial-state fluctuations should still scale Roy A. Lacey, Stony Brook University, QM2014

  30. Flow is partonic & Acoustic? arXiv:1211.4009 Note species dependence for all vn For partonic flow, quark number scaling expected  single curve for identified particle species vn Roy A. Lacey, Stony Brook University, QM2014

  31. Scaling properties of flow Acoustic Scaling – Ratios vn PID scaling Roy A. Lacey, Stony Brook University, QM2014

  32. Acoustic Scaling – 1/R Compare system size @ RHIC Slope difference encodes viscous coefficient difference • Viscous coefficient larger for more dilute system Roy A. Lacey, Stony Brook University, QM2014

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