PHENIX

Motivation Collaboration

PHENIX Roy A. Lacey (SUNY Stony Brook) PHENIX Collaboration I N T E R N A T I O N A L W O R K S H O P O N T H E P H Y S I C S O F T H E Q U A R K - G L U O N P L A S M A

PHENIX Motivation The Notion of an EOS /Phase Transitions is Pervasive

PHENIX Motivation Which Observable Provides an Important Opportunity to Probe the EOS and QGP Formation ? Elliptic Flow (Differential Elliptic Flow)

PHENIX Elliptic Flow Low Energy: ---- Squeeze-out High Energy : In-plane Emission Low Energy: ---- Squeeze-out High Energy : In-plane Emission Azimuthal Asymmetry in the Flow of Particle Momentum or Energy

PHENIX Elliptic Flow The Transition from Negative to Positive Elliptic Flow Occurs ~ 4 AGeV The Transition from Negative to Positive Elliptic Flow Occurs ~ 4 AGeV

PHENIX Elliptic Flow The Driving Forces for Elliptic Flow are Understood The Driving Forces for Elliptic Flow are Understood Differential Elliptic Flow Studies are Important Differential Elliptic Flow Studies are Important The Driving Forces for Elliptic Flow are Understood The Driving Forces for Elliptic Flow are Understood Differential Elliptic Flow Studies are Important Differential Elliptic Flow Studies are Important d1d1 d2d2

PHENIX RHIC ? l Significant Variation in the Energy Density Variations~ x 3 Variations~ x 3 Lattice Calculations - Phase Transition ~ 1 GeV/fm 3 A Wide Range Energy Densities are Accessible at RHIC PHENIX 2% Central ~ 4.6 GeV/fm 3

PHENIX The onset of QGP provides a Characteristic Signal Differential Elliptic Flow Sorge

PHENIX Analysis Study Correlation between particles: Event by event reaction plane determination & Dispersion Corrections Circumvented Event by event reaction plane determination & Dispersion Corrections Circumvented Reduced Uncertainties associated with Acceptance, efficiency Reduced Smaller Signal !!

PHENIX Correlation Function Good Signal to Noise Wang et al., PRC 44, 1091 (1991) Lacey et al. PRL 70, 1224 (1993)

PHENIX Centrality Selection 5-10% 10-15% 15-20% 0-5 % “Spectators” “Participants”.

PHENIX Correlation Functions Anisotropy Shows Clear CentralityAnd pT Dependence Anisotropy Shows Clear CentralityAnd pT Dependence Viable Method Anisotropy Shows Clear CentralityAnd pT Dependence Anisotropy Shows Clear CentralityAnd pT Dependence Viable Method

PHENIX Strong pt Dependence PHENIX Preliminary Differential Flow (p t, cent)

PHENIX STARPHENIX Reasonable Agreement Between Experiments Differential Flow (p t )

PHENIX What Does the pT Dependence Tell You ? Strong Velocity Field Required for pt dependence Huovinen QM01 Differential Flow (p t )

PHENIX E895 Rapidity Dependence due to Sidewards Flow PHOBOS Extensive Pseudorapidity reach by PHOBOS Differential Flow ( )

PHENIX Hirano et al. Differential Flow ( ) For large pseudorapidity -- Thermalization ? Longitudinal expansion ?

PHENIX Sizeable Centrality Dependence Sizeable Centrality Dependence Pt cuts enhance the centrality dependence Pt cuts enhance the centrality dependence Differential Flow (cent, p t ) Spatial Asymmetry  Momentum Asymmetry Compatible with Rapid Thermalization Separate effects Of pT and Centrality (Scaled Elliptic Flow)

PHENIX The onset of QGP provides a Characteristic Signal Differential Elliptic Flow Sorge

PHENIX Scaled Differential Flow (cent, p t ) Scaled Elliptic Flow Suggestive !! High pT probe earlier Times and Larger Energy Densities ??

PHENIX Flow Measurements can serve as an important probe of Nuclear Matter at high energy density  At RHIC  Sizeable Integral and Differential Elliptic flow Observed  Separate Effects of Geometry and Dynamics can be Identified  pT dependence – strong velocity fields  cent dependence – Rapid Thermalization  Rapidity dependence – Energy Density profile ??  Scaling for low pT particles Mixed Phase for mid-central collisions ??  Larger Flow for central collisions for High pT hadrons -- Mixed Phase for mid-central collisions ?? Exciting and Interesting Work Lay Ahead