What have we learned from RHIC, So far? RHIC has taken data in: 2001: AuAu (130GeV) 2002: AuAu, pp(200 GeV) 2003: pp, dAu (200 GeV)  Any nucleus on any other.  Top energies (each beam): 100 GeV/nucleon Au-Au. 250 GeV 2 counter- circulating rings, 3.8 km circumference polarized polarized p-p.

95°95° 30° 15° 2.3° STAR BRAHMS PHENIX

Russia: MEPHI - Moscow LPP/LHE JINR - Dubna IHEP - Protvino U.S. Laboratories: Argonne Berkeley Brookhaven U.S. Universities: UC Berkeley UC Davis UC Los Angeles Carnegie Mellon Creighton University Indiana University Kent State University Michigan State University City College of New York Ohio State University Penn. State University Purdue University Rice University Texas A&M UT Austin U. of Washington Wayne State University Yale University Brazil: Universidade de Sao Paulo China: IHEP – Beijing IMP - Lanzou IPP – Wuhan USTC SINR – Shanghai Tsinghua University Great Britain: University of Birmingham France: IReS Strasbourg SUBATECH - Nantes Germany: MPI – Munich University of Frankfurt India: IOP - Bhubaneswar VECC - Calcutta Panjab University University of Rajasthan Jammu University IIT - Bombay VECC – Kolcata Poland: Warsaw University of Tech. The STAR Collaboration

High Density QCD Matter in Laboratory Determine its properties QCD Prediction: Phase Transitions Deconfinement to Q-G Plasma Chiral symmetry restoration Relevance to other research areas? Quark-hadron phase transition in early Universe Cores of dense stars High density QCD Phases of QCD

Preliminary  s NN = 200 GeV Uncorrected participants spectators peripheral (grazing shot) central (head-on) collision Centrality classes based on mid-rapidity multiplicity N part (Wounded Nucleons) ~ soft production N bin ~ hard processes Centrality and Participants in HI

5% central 15% Central Au ZDC Symmetric Zero Degree Calorimeters Central Trigger Barrel Triggering Capabilities

Understanding “Bulk” Matter Studying Matter: –Global Observables N ch,  E T ,  p T   , S, … –Particle Yields & Ratios  T ch,  B,  S, … –Particle Spectra  T fo, flow, stopping, … –Correlations –… and all that in pp, pA, AA STAR preliminary 99.5%

Rapidity Density PHOBOS Central Au+Au (200 GeV) Compilation by K. Eskola Multiplicity at low end of range –But: Energy density 30x nuclear matter Most models didn’t do so well PHOBOS multiplicity papers: Phys. Rev. Lett. 85, 3100 (2000) Phys. Rev. Lett. 87, (2001) Phys. Rev. C 65, 31901R (2002) Phys.Rev. Lett. 88, (2002) Phys. Rev. C 65, R (2002) nucl-ex/ , PRL in Press nucl-ex/ , subm. to PRL Particle Production

RHIC: N ch at mid-rapidity Consistency of RHIC results PHENIX: PC, STAR: TPC PHOBOS: Si BRAHMS: Si & Scint. PHENIX & STAR preliminary Ratio R(200/130): BRAHMS:1.14  0.05 PHENIX: 1.17  0.03 PHOBOS: 1.14  0.05 STAR:1.19  (no sys. yet)

Nch(  s NN ) – Universality of Total Multiplicity? pQCD e + e - Calculation Total charged particle multiplicity / participant pair Accidental, trivial? Is plain parton fragmentation all there is in AA above  s ~ 20 GeV? (A. Mueller, 1983) Same for all systems at same  s(  s eff for pp)

N ch : Centrality Dependence at RHIC (SPS) _ pp PHOBOS Au+Au |  |< GeV preliminary 130 GeV 200 GeV Au+Au (preliminary) Everything counts: N ch |  =0 described nicely by KN (hard + soft)  N ch  scales with N part

Rapidity Spectra: Boost-Invariance at RHIC ? M. Baker (PHOBOS) D. Ouerdane (BRAHMS)

 E T  /  N ch  from SPS to RHIC Independent of energy Independent of centrality PHENIX preliminary Surprising fact: SPS  RHIC: increased flow, all particles higher  p T  still  E T  /  N ch  changes very little Does different composition (chemistry) account for that?

Ratios, Ratios, Ratios …. Huge amount of results from all 4 RHIC experiments: systematic studies of:  - /  +, K - /K +,  p/p  / ,  / ,  / ,  / p, K / ,  / ,  / h,  K, K*/K, … –many as function of p T, N part –at  s of (20), 130, and 200 GeV –with and without feed-down correction (   ) BRAHMS  large y coverage and reach to high p T PHENIX  reach to high p T STAR  multi-strange baryons

NEW: Rapidity dependence of ratios at RHIC BRAHMS 200 GeV At mid-rapidity: Net-protons: dN/dy  7 proton yield: dN/dy  29  ¾ of all protons from pair-production

p/  Proton yield is comparable with 2 GeV in central collisions, less in peripheral Central Peripheral

Statistical Model: First Look at 200 GeV Predictions: phenomenologically:  B ~ 1.3 GeV (1+  s/4.5 GeV) -1 assume unified freeze-out condition:  E  /  N  ~ 1.1 GeV  T

Statistical Models: from AGS to RHIC Fit by Beccatini using total yields from NA49 hadron gas fit with partial strangeness saturation Different implementation of statistical model (Kaneta/Nu, Beccatini, PBM et al., …) Fact: all work well at AGS, SPS and RHIC Slight variations in the models, but roughly: T ch [MeV]  B [MeV] AGS SPS RHIC17530 Does the success of the model tells us we are dealing indeed with locally chemically equilibrated systems? this+flow  If you ask me YES!

Anisotropic flow from AGS to RHIC Outline: 1.Directed flow (techniques, models, results) 2.Elliptic flow (techniques, models, results) 3.Elliptic flow at high pt’s. 4.Open questions Directed flowElliptic flow Anisotropic flow  correlations with respect to the reaction plane X Z XZ – the reaction plane Picture: © UrQMD

What flows and when? prediction with T th and obtained from blastwave fit (green line) prediction for T ch = 170 MeV and =0 pp no rescattering, no flow no thermal equilibrium STAR preliminary F. Wang  and  appear to deviate from common thermal freeze-out Smaller  elast ? Early decoupling from expanding hadronic medium? Less flow? What’s about partonic flow?