CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 1 Nu Xu Lawrence Berkeley National Laboratory Part I: QM04 Highlights (experiment) Part II: Transverse Dynamics at RHIC

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 2 QM04 Highlights Part I

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 3 Quark Matter Conference

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 4 Blue Ring (clockwise) Yellow Ring ARC Four Experiments: BRAHMSPHENIX PHOBOSSTAR ~ 1200 physicists: high energy/nuclear Started in the Summer of 2000 ~ 200 publications (summer ‘04)

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 5 Brookhaven National Laboratory h STAR PHENIX PHOBOS BRAHMS

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 6 Colliding Systems Run-I19.6 GeVAu+Au GeVAu+Au2000 Run-II 200 GeVAu+Au GeVp+p2001 Run-III200 GeVd+Au2002 Run-IV200 GeVAu+Au2004

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 7 People at RHIC More than 1000 people from around the world Brazil, Canada, China, Croatia, Denmark, France, Germany, India, Israel, Japan, Korea, Norway, Poland, Russia, Sweden, UK, USA

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 8 Identify and study the properties of matter with partonic degrees of freedom. Penetrating probes Bulk probes - direct photons, leptons - spectra, v 1, v 2 … - “jets” and heavy flavor - partonic collectivity - fluctuations jets - observed high p T hadrons (at RHIC, p T(min) > 3 GeV/c) collectivity - collective motion of observed hadrons, not necessarily reached thermalization among them. Physics Goals at RHIC Hydrodynamic Flow Collectivity Local Thermalization = 

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 9 P hase diagram of strongly interacting matter CERN-SPS, RHIC, LHC: high temperature, low baryon density AGS, GSI (SIS200): moderate temperature, high baryon density

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 10 QCD on Lattice Lattice calculations predict T C ~ 170 MeV 1) Large increase in  a fast cross cover ! 2) Does not reach ideal, non-interaction S. Boltzmann limit !  many body interactions  Collective modes  Quasi-particles are necessary 3) T C ~ 170 MeV robust! Z. Fodor et al, JHEP 0203:014(02) Z. Fodor et al, hep-lat/ C.R. Allton et al, hep-lat/ F. Karsch, Nucl. Phys. A698, 199c(02).

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 11 Study of Nuclear Collisions Like… P.C. Sereno et al. Science, Nov. 13, 1298(1998). (Spinosaurid) BulkProperties High p T - QCD probes

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 12 Au + Au Collisions at RHIC STAR Central Event (real-time Level 3)

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 13 Collision Geometry, Flow x z Non-central Collisions Number of participants: number of incoming nucleons in the overlap region Number of binary collisions: number of inelastic nucleon-nucleon collisions Charged particle multiplicity  collision centrality Reaction plane: x-z plane Au + Au  s NN = 200 GeV

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 14 Global: Charge hadron density 19.6 GeV 130 GeV 200 GeV Charged hadron pseudo-rapidity  1) High number of N ch indicates initial high density; 2) Mid-y, N ch  N part  nuclear collisions are not incoherent; 3) Saturation model works Important for high density and thermalization. PRL 85, 3100 (00); 91, (03); 88, (02), 91, (03) PHOBOS Collaboration

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 15 Particle production at RHIC Bulk production Collective effects New form of matter pQCD Soft (hydro) GeV/c Large Q 2 results Medium modification of hard probes - parton energy loss Unclear region New observations

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 16 High/Intermediate p T 1)Expect QCD calculations can be used as guidance 2)New tool at high energy nuclear collisions

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 17 Energy Loss in A+A Collisions Nuclear Modification Factor: back-to-back jets disappear leading particle suppressed p+p Au + Au

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 18 Jet Quenching Hadron suppression at intermediate p T, caused by energy loss of energetic objects, - ‘Jet quenching’!

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 19 Jets Observation at RHIC p+p collisions at RHIC Jet like events observed Au+Au collisions at RHIC Jets? 

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 20 Suppression and correlation Hadron suppression and disappearance of back-to-back ‘jet’ are correlated!

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 21 Di-jet tomography: Predictions In-plane Out-of-plane X.N. Wang dE/dx  path length L!

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 22 Di-hardron tomography p T trig = GeV/c, |  |<1.0, 2.0<p T assoc <p T trig - Back-to-back suppression depends on the reaction plane orientation: i.e. energy loss dependence on the path length -Powerful tool to study hadronization process in heavy ion collisions A. Tang QM04 STAR Preliminary 20-60% STAR preliminary

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 23 Energy loss and equilibrium Leading hadrons Medium In Au +Au collision at RHIC: - Suppression at the intermediate p T region - energy loss cause by the final state interactions - The energy loss leads to progressive equilibrium in Au+Au collisions STAR: nucl-ex/

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 24 Direct  : a colorless probe 1 + (  pQCD direct x N coll ) / (  phenix pp backgrd x N coll ) PHENIX Preliminary (PbGl / PbSc Combined) 1 + (  pQCD direct x N coll ) /  phenix backgrd Vogelsang NLO PHENIX: Direct photons are described by a curve that includes the measured suppressed  0 production in Au+Au collisions. (Au+Au at 200 GeV: 0-10%) Transverse momentum p T (GeV/c)

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 25 R AA for  0 in Central Collisions D. d’Enterria QM04 nucl-ex/ SPS Energies: A.L.S.Angelis, PL B185, 213 (87) WA98, EPJ C23, 225 (2002) RHIC Energies: PHENIX, PRL (02) PRL 91, (03) p+p collision results changed Finite energy loss in central heavy ion collisions at SPS energies!

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 26 Summary: High/Intermediate p T 1)From run I - III, particle spectra were measured up to p T ~10-12 GeV/c; 2)Energy loss effect observed at intermediate region in central Au+Au collisions at 200GeV; 3)Back-to-back ‘jets’ disappears; 4)The energy loss depends on the path length - new! Future: Cronin effect - energy, hadron type dependence Hadronization process in p+p and Au+Au collisions Origin of v 2 at intermediate p T region (2-6 GeV/c) …

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 27 Open Charm Production 1)Production through gluon fusing - sensitive to the initial condition for heavy ion collisions 2)Interacting with medium - sensitive to medium properties 3)Heavy intrinsic mass - a test the predictive power of QCD calculation

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 28 QCD Energy Scale s-quark mass ~ 0.2 GeV, similar to values of T C critical temperature  QCD QCD scale parameter T CH chemical freeze-out temperature   = 4  f  chiral breaking scale mCmC c-quark mass ~ GeV >>  QCD -- pQCD production - parton density at small-x -- QCD interaction - medium properties R cc ~ 1/m C => color screening J/  => deconfinement and thermalization heavy-flavors u-, d-, s-quarks: light-flavors || c-, b-quarks: heavy-flavors 1/x

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 29 Electron spectra An increasing excess found at higher p T region, p T > 1.0 GeV/c,  Expected contribution of semi-leptonic decays from heavy flavor hadrons STAR Preliminary

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 30 Consistent in D measurements Directly reconstructed D mesons D and electron spectra are consistent! STAR: nucl-ex/ STAR Preliminary Electrons from D decay

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 31 Open Charm spectra An increasing excess found at higher p T region, p T > 1.0 GeV/c,  Expected contribution of semi-leptonic decays from heavy flavor hadrons  pQCD distributions are steeper and total cross sections are lower CGC: D. Kharzeev and K. Tuchin, NPA735, 248(04). STAR: nucl-ex/0406

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 32 Charm production cross-section 1) NLO pQCD calculations under-predict the ccbar production cross section at RHIC 2)Power law for ccbar production cross section from SPS to RHIC: n ~ 2 (n~0.5 for charged hadrons) 3)Large uncertainties in total cross section due to rapidity width, model dependent(?). STAR Preliminary

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 33 Some SPS results

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 34 NA49 Experiment NA49 Experiment Pb+Pb collision at 158A GeV

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 35 Rapidity spectra (open dots from reflection at y cm = 0) Extrapolation  4π yields also: , 

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 36 Statistical model at at 40A, 80A GeV At lower energies  B increases, while T decreases slightly

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 37 Particle yields – statistical model hadron species populated according to phase space probabilities (max.entropy) (Fermi,Hagedorn) strangeness sector not fully saturated (Rafelski) statistical model successful, T,  B,  S, V larger value of  S in A+A due to relaxation of local strangeness conservation (fits by F.Becattini et al, PRC69(2004)024905)

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 38 Ratio of strange hadrons to pions hadronic mixed partonic Strangeness to pion ratio peaks sharply at the SPS  deconfinement? hadronic mixed partonic

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 39 Mid-rapidity transverse mass spectra 158A GeV well described by fireball model assuming common temperature and flow “blast wave”: (Schnedermann,Sollfrank, Heinz : PRC 48 (1993) 2462)

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 40 Part I: summary Topics are not covered: Color Glass Condensation: small-x cold QCD physics Peripheral collisions at RHIC HBT issues at RHIC Astrophysics and heavy ion collisions New theoretical development

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 41 Transverse Dynamics at RHIC Part II

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 42 Pressure, Flow, …  d  = dU + pdV  – entropy; p – pressure; U – energy; V – volume  = k B T, thermal energy per dof In high-energy nuclear collisions, interaction among constituents and density distribution will lead to: pressure gradient  collective flow  number of degrees of freedom (dof)  Equation of State (EOS)  No thermalization is needed – pressure gradient only depends on the density gradient and interactions.  Space-time-momentum correlations!

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 43 Transverse flow observables As a function of particle mass: Directed flow (v 1 ) – early Elliptic flow (v 2 ) – early Radial flow – integrated over whole evolution Note on collectivity: 1) Effect of collectivity is accumulative – final effect is the sum of all processes. 2) Thermalization is not needed to develop collectivity - pressure gradient depends on density gradient and interactions.

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 44 Hadron spectra from RHIC p+p and Au+Au collisions at 200 GeV

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 45 Hadron production & chemical freeze-out 1) Chemical fit well to all hadron ratios at RHIC: T ch = 160 ± 10 MeV  B = 25 ± 5 MeV  S = 1 ± 0.05 Necessary for QGP! 2) The temperature parameter T ch is close to the critical temperature T C predicted by LGT calculations  chemical equilibrium at the phase boundary 3) Since 1999, many work in this direction Review: P. Braun-Munzinger et al. nucl-th/

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 46 Compare with hydrodynamic model This model results fit to pion, Kaon, and proton spectra well, but over predicted the values of for multi-strange hadrons

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 47 Hydro model: for , , p spectra

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 48 Thermal model fit Source is assumed to be: –Local thermal equilibrated –Boosted radically random boosted E.Schnedermann, J.Sollfrank, and U.Heinz, Phys. Rev. C48, 2462(1993)

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 49 Early freeze-out Central Au+Au collisions at RHIC 1) Multi-strange hadrons seem to freeze out earlier than others  sensitive probe for early dynamics 2) Charm-hadrons should be better. A possible complication is the pQCD hard spectrum. 3) J/  coalescence/melting: a tool for early dynamics CGC, deconfinement, and thermal equilibrium PHENIX: Phys. Rev. C (04). STAR: Phys. Rev. Lett. 92, (04); Phys. Rev. Lett. 92, (04). A. Andronic et al., NPA715, 529(03). P. Kolb et al., Phys. Rev. C (03) Chemical Freeze-out: inelastic interactions stop Kinetic Freeze-out: elastic interactions stop

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 50 Blast wave fits: T fo vs. 1) , K, and p change smoothly from peripheral smoothly from peripheral to central collisions. to central collisions. 2) At the most central collisions, reaches collisions, reaches 0.6c. 0.6c. 3) Multi-strange particles ,  are found at higher T  are found at higher T and lower and lower  Sensitive to early partonic stage!  Sensitive to early partonic stage!  How about v 2 ?  How about v 2 ? STAR: NPA715, 458c(03); PRL 92, (04); 92, (04). 200GeV Au + Au collisions

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 51 Equation of State Equation of state: - EOS I : relativistic ideal gas: p =  /3 - EOS H: resonance gas: p ~  /6 - EOS Q: Maxwell construction: T crit = 165 MeV, B 1/4 = 0.23 GeV  lat =1.15 GeV/fm 3 P. Kolb et al., Phys. Rev. C62, (2000). With given degrees of freedom, the EOS - the system response to the changes of the thermal condition - is fixed by its p and T(  ). Energy density  GeV/fm 3

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 52 y x pypy pxpx coordinate-space-anisotropy  momentum-space-anisotropy Anisotropy parameter v 2 Initial/final conditions, EoS, degrees of freedom

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 53 v 2 at Low p T - At low p T, hydrodynamic model fits well for minimum bias events indicating early thermalization in Au+Au collisions at RHIC! - More theory work needed to understand details: such as centrality dependence of v 2 ; consistency between spectra and v 2 … P. Huovinen, private communications, 2004

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 54 Partonic collectivity at RHIC v 2, the spectra of multi- strange hadrons, and the scaling of the number of constituent quarks  Partonic collectivity has been attained at RHIC!  Deconfinement, model dependently, has been attained at RHIC! Next question is the thermalization of light flavors at RHIC: - v 2 of charm hadrons - J/  yield, distributions PHENIX: PRL91, (03) STAR: PRL92, (04)

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 55 Nuclear modification factor 1) Baryon vs. meson effect! 2) Hadronization via coalescence 3) Deconfinement at RHIC - (K 0,  ): PRL92, (04); NPA715, 466c(03); - R. Fries et al, PRC68, (03)

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 56 Freeze-out systematics The additional increase in  T is likely due to partonic pressure at RHIC. 1) Smaller baryon chemical potential  B = 25 MeV with T ch = 160 MeV 2) Stronger transverse flow,  T = 0.6(c)

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 57 STAR 200 GeV v 2 Anti-proton fit well by the hydrodynamic model with initial velocity kick (  = 0.02fm -1 ), but pions fail! Much more theory work ahead P. Kolb and R. Rapp, Phy. Rev. C67, (2002)

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 58 Partonic collectivity at RHIC 1) Copiously produced hadrons freeze-out: T fo = 100 MeV,  T = 0.6 (c) >  T (SPS) 2)* Multi-strange hadrons freeze-out: T fo = 170 MeV (~ T ch ),  T = 0.4 (c) 3)** Multi-strange v 2 : Multi-strange hadrons  and  flow! 4)*** Constituent quark scaling: Seems to work for v 2 and R AA (R CP )  Partonic (u,d,s) collectivity at RHIC

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 59 Summary (1) Flavor equilibration - necessary for QGP (2) Jet energy loss - QCD at work (3) Collectivity - pressure gradient ∂P QCD Deconfinement and Partonic collectivity First time ever, re-produced partonic matter in the laboratory since big bang.

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 60 P hase diagram of strongly interacting matter CERN-SPS, RHIC, LHC: high temperature, low baryon density AGS, GSI (SIS200): moderate temperature, high baryon density GSI200 RHIC LHC Discover QGP and more!

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 61 Some Future reading: Quark Matter conference proceedings 2002 Nucl.Phys. A715, 1c(2003). - Quark Matter conference proceedings 2001 Nucl.Phys. A698, 1c(2002). - “Introduction to High Energy Heavy Ion Collisions’’ - By C.Y. Wong (Oak Ridge), Singapore, Singapore: World Scientific (1994) 516 p. - “Introduction to Relativistic Heavy Ion Collisions’’ - By L.P. Csernai (Bergen U.), Chichester, UK: Wiley (1994) 310 p. - Recent discussions on the QGP discovery

CCAST, Beijing, China, 2004 Nu Xu //Nxu/tex3/TALK/2004/08CCAST 62