The Energy scan at RHIC Roy A. Lacey ``Search for the critical point ’’ Roy A. Lacey Chemistry Dept. Stony Brook University International Workshop on Hot and Cold Baryonic Matter 2010

A Central Question of the Field Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Phase Diagram (H2O) This knowledge is elemental to the phase Water subjected to high pressure and temperature A fundamental understanding requires knowledge of: The location of the Critical End Point (CEP) The location of phase coexistence lines The properties of each phase This knowledge is elemental to the phase diagram of any substance ! Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Schematic QCD phase diagram Both experiment and theory indicate a continuous/rapid crossover transition from the QGP to hadronic matter Our understanding of the QCD Phase diagram, as well as the properties of the different phases is still fairly limited Strongly or weakly coupled? Critical point? Coexistence curves? Properties of each phase? Significant experimentation is required at several facilities to gain further insight! Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

The Crossover is a necessary requirement for existence 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, as well as new techniques for studying the properties of QCD matter! Lattice results Space-time measurements Flow Measurements Jet Quenching The Crossover is a necessary requirement for existence the CEP Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Results from Lattice Calculations Hot QCD Collab Aoki et al Lattice calculations indicate a crossover transition The EOS is an important outcome Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Indications of a crossover from space-time Measurements Hydrodynamic prediction Anatomy of a RHIC collision Courtesy S. Bass initial state pre-equilibrium QGP and hydrodynamic expansion hadronization hadronic phase and freeze-out Puzzle ? hadronization Koonin Pratt Eqn. Correlation function Encodes FSI Source function (Distribution of pair separations) A Cross Over strongly affects the Space-time Dynamics Inversion of this integral equation  Source Function Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

The transition is Not a Strong First order Phase Transition?   Phys. Rev. Lett. 100, 232301 (2008) Therminator: A.Kisiel et al. Comput.Phys.Commun.174, 669 (2006) Thermal model with Bjorken longitudinal expansion and transverse Flow Spectra & yields constrain thermal properties Transverse radius ρmax : controls transverse extent Breakup time in fluid element rest frame, : controls longitudinal extent Emission duration : controls tails in long and out directions a controls x-t correlations Source Function Comparison to Models Give robust life time estimates  Consistent with Crossover transition Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

The scaling properties of vn and RAA constitutes an important probe! They lend profound insights, as well as constraints for estimates of transport coefficients! Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Quenching Measurements Nuclear Modification Factor Jet Quenching Nuclear Modification Factor Radiative energy loss Dead cone effect Phys. Lett. B519, 199 (2001) Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Scaling of Jet Quenching Phys.Rev.C80:051901,2009 Phys.Rev.Lett.103:142302,2009 Minimum L Requirement i.e. no corona quenching Scaling also validated for different system size etc! Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Scaling of Jet Quenching - Reaction plane dependence Estimates From slope Simultaneous scaling of RAA and v2 Further validation of path length scaling! Very important but no new information! Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Is Jet Quenching Anomalous? Phys.Rev.Lett.103:142302,2009 ~3 GeV Different Minimum L Requirement? i.e. no corona quenching Quenching compatible with anisotropy  Anomalous quenching? Future B & D measurements (RAA & v2) at high pT will help! Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Universal scaling of harmonic flow at RHIC Phys. Rev. Lett. 98, 162301 (2007) Mesons Baryons v2 scaling v4 scaling Universal scaling KET & nq (nq2) scaling validated for v2 (v4)  Partonic flow Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Flow scales across centrality PHENIX Preliminary PHENIX Preliminary PHENIX Preliminary PHENIX Preliminary PHENIX Preliminary PHENIX Preliminary KET & nq (nq2) scaling validated for v2 as a function of centrality Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010 15

η/s from hadronic phase is very large 10-12x(1/4π) Scaling of the Φ Demir et al η/s from hadronic phase is very large 10-12x(1/4π) No room for such values! Partonic flow dominates! Hadronic contribution cannot be large Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

PHENIX Preliminary Run7 Charm flows and scales PHENIX Final Run4 PHENIX Preliminary Run7 Minimum bias van Hees et al. Au+Au at √sNN = 200 GeV J/ v2 still challenged by statistics Strong coupling η/s - estimate Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Extraction of transport coefficient Ideal hydro Estimate  4π(η/s) ~ 1- 2 Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Extraction of transport coefficient h/s ~ 0 h/s = 1/4p h/s = 2 x 1/4p h/s = 3 x 1/4p Extracted η/s is small Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

apparent viscous corrections decrease with pT Knudsen Fits For pT > 3 GeV/c apparent viscous corrections decrease with pT Excellent simultaneous fits achieved Viscous corrections grow with pT Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Viscous Corrections Onset of suppression! CGC Glauber Quadratic dependence of δf Breakdown of hydrodynamic ansatz for K* ~ 1 Onset of jet suppression Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Opportunities with an energy scan Onset of deconfinement onset of quark number scaling onset of charge asymmetry absence of “flux tubes” Growth of viscosity Constraints for the EOS Evidence for first order phase transition Critical point search Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Light Quark Opacity Phys.Rev.C80:051901,2009 At what collision energy does the onset of light quark opacity occur?; what drives it?; additional constraint ĝ? Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Heavy Quark Opacity PRL 98, 172301 (2007) RAA~1 Au+Au 64 GeV nucl-ex/0610029 Where ( ) is the onset of heavy quark opacity?; what drives it?; Why a different energy range?; constraints? Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Onset of Quark Number Scaling? DATA (KAOS – Z. Phys. A355 (1996); (E895) - PRL 83 (1999) 1295 Passing time scaling at very low energy particle-mass scaling at very low energy Where ( ) is the onset of quark number scaling? Relationship to Quark dof ? Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

New Constraints for the Hadronic EOS? Danielewicz, Lacey, Lynch EOS not very well constrained experimentally Soft and hard EOS Further constraints for the hadronic EOS Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

QCD Critical End Point Search for the CEP is now a central objective ``The discovery of the critical point would in a stroke transform the map of the QCD phase diagram from one based only on reasonable inference from universality, lattice gauge theory and models into one with a solid experimental basis’’ Krishna Rajagopal – Phys.Rev.D61:105017,2000 Knowledge of the position of the CEP is a powerful constraint on possible models of QCD thermodynamics Search for the CEP is now a central objective Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Theoretical Guidance for CEP ? Chemical Freeze-out Curve Theoretical Guidance for CEP ? Theoretical Predictions from Lattice QCD Intriguing predictions but search for the CEP requires experimental investigations over a broad range of μ & T. Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Which search variable/s? Operational Ansatz The physics of the critical point is universal. Members of a given universality class show “identical” critical properties Stationary state variables Dynamic variables The CEP belongs to the same dynamic universality class (Model H) as the liquid gas phase transition Son & Stephanov Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Singular behavior of stationary state Stephanov, Rajagopal,Shuryak, variables near the CEP Stephanov, Rajagopal,Shuryak, Phys. Rev. D 60, 114028 (1999) Fluctuations Correlation length Divergence of ξ restricted: Finite system size ξ < size Finite evolution time ξ < (time)1/z z=3 Non-monotonic dependence of event-by-event fluctuations as a function of Net proton number fluctuation Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Focusing of Isentropic Trajectories CEP Search with CEP Focusing of Isentropic Trajectories steeper spectra at high PT Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Singular behavior of Dynamic variables near the CEP Son & Stephanov, Diffusion Constant Correlation length viscosity Divergence of ξ restricted: Finite system size ξ < size Finite evolution time ξ < (time)1/z z=3 D “vanishes’’ at the CEP “mild’’ dependence for viscosity Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Viscosity estimates at AGS - SPS Significant deviations Ivanov et al Significant deviations From hydrodynamic calculations From fits Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

is a potent signal for the CEP The CEP belongs to the Model H dynamic universality class -Son & Stephanov Lacey et al. arXiv:0708.3512 [nucl-ex] is a potent signal for the CEP Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Lacey et al. arXiv:0708.3512 [nucl-ex] Meyer Kharzeev-Tuchin CEP Search Lacey et al. arXiv:0708.3512 [nucl-ex] Search in the region Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010

Summary The RHIC energy scan has been initiated Analysis of data from the initial scan underway Broad range of variables under investigation Additional beam collision energies expected in 2011 Stay tuned for a robust set of analysis results Roy A. Lacey, Stony Brook University; Hot and Cold Baryonic Matter, Budapest, Aug. 15 – 20, 2010