2. RNM meeting FIAS, Frankfurt, 22 Feb 2006 1 Hunt for the QGP at RHIC Kai Schweda, University of Heidelberg S. Blyth, A. Dainese, T. Dietel, X. Dong, J. Faivre, Y. Lu, M. Oldenburg, H.G. Ritter, L. Ruan, A. Shabetai, P. Sorensen, N. Xu, H. Zhang, Y. Zhang.

3. RNM meeting FIAS, Frankfurt, 22 Feb 2006 2 Outline 1)Introduction 2)High-p T Suppression 3)Bulk properties: - Hadron abundances - Heavy-Flavor (c,b) Collectivity 4)Summary

4. RNM meeting FIAS, Frankfurt, 22 Feb 2006 3 Quark Gluon Plasma Source: Michael Turner, National Geographic (1996) Quark Gluon Plasma: (a)Deconfined and (b)thermalized state of quarks and gluons  Study partonic EOS in high energy nuclear collisions (?) Probe thermalization using heavy-quarks

5. RNM meeting FIAS, Frankfurt, 22 Feb 2006 4 Phase Diagram

6. RNM meeting FIAS, Frankfurt, 22 Feb 2006 Au +Au@ 20, 62, 130, 200 GeV Cu + Cu@ 20, 62, 200 GeV d + Au@ 200 GeV p + p@ 200, 400 GeV

7. RNM meeting FIAS, Frankfurt, 22 Feb 2006 6 Peripheral Event STAR Au + Au Collisions at RHIC (real-time Level 3)

8. RNM meeting FIAS, Frankfurt, 22 Feb 2006 7 STAR Mid-Central Event Au + Au Collisions at RHIC (real-time Level 3)

9. RNM meeting FIAS, Frankfurt, 22 Feb 2006 8 Au + Au Collisions at RHIC STAR Central Event (real-time Level 3)

10. RNM meeting FIAS, Frankfurt, 22 Feb 2006 9 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 (|  | < 0.75)

11. RNM meeting FIAS, Frankfurt, 22 Feb 2006 10 Hadron spectra from RHIC p+p and Au+Au collisions at 200 GeV White papers - STAR: Nucl. Phys. A757, p102;

12. RNM meeting FIAS, Frankfurt, 22 Feb 2006 11 Two Different Ways to Probe Bulk Use high p T as probeProbe the bulk responsePartons lose energy in medium Response of medium to pressure Measure nuclear modification factor R AA Measure elliptic flow v 2 Partonic energy loss dE/dx, gluon density Partonic equation of state EoS I believe, they are all correlated: back-back, R_AA, v2,… Interactions !

13. RNM meeting FIAS, Frankfurt, 22 Feb 2006 12  Fast partons emits gluons  energy loss  Energy loss depends on color charge density  Measure  E  color (~gluon) density in dense phase Dominant Process: Gluon Bremsstrahlung hadrons leading particle suppressed q q ? Partonic Energy Loss

14. RNM meeting FIAS, Frankfurt, 22 Feb 2006 13 hadron s leading particle suppress ed q q ? After the initial hard-scattering, the parton interacts strongly with the dense medium in central Au+Au collisions Observation of Jet Quenching

15. RNM meeting FIAS, Frankfurt, 22 Feb 2006 14 Energy Loss and Equilibrium Leading hadrons Medium  Suppression at intermediate p T - caused by final state interactions  Energy loss leads to progressive equilibrium in Au+Au collisions

16. RNM meeting FIAS, Frankfurt, 22 Feb 2006 15 Photon – Hadron Correlations* *STAR analysis: T. Dietel; nucl-ex/0510046.  First high-p T correlations !  No background subtraction !  Same-side: increasing contributions from  -jet events  Away-side: different suppression for di-jet vs  -jets  First step towards  -jet  Detailed energy loss studies !

17. RNM meeting FIAS, Frankfurt, 22 Feb 2006 16 If no “effects”:  R < 1 in regime of soft physics  R = 1 at high-p T where hard scattering dominates Suppression ?  Is R < 1 at high-p T ? Nuclear Modification Factor Quantify deviations from expected behaviour in p+p collisions: /  inel p+p (Nuclear Geometry)

18. RNM meeting FIAS, Frankfurt, 22 Feb 2006 17  Large Suppression in central Au + Au  Suppression is absent in d-Au collisions  Final state effect  Partonic energy loss Initial or Final State?

19. RNM meeting FIAS, Frankfurt, 22 Feb 2006 18 Heavy-flavor Energy Loss Heavy-flavor decay electrons: Probe interaction with medium b,c  e + X  Induced gluon radiation only  Plus elastic collisions  Better agreement with data  Heavy flavor energy loss not fully understood ! Calculations: M. Djordjevic et al.

20. RNM meeting FIAS, Frankfurt, 22 Feb 2006 19 Partonic Energy Loss at RHIC (1) Intermediate/high pT: spectra suppressed and ratios start to decrease at p T ~ 2 GeV/c (2) Jet-like behavior observed in correlations - hard scatterings in AA collisions - disappearance of back-to-back correlations - energy gets largely deposited in the bulk medium  Partonic energy loss at RHIC ! (3) Heavy-flavor energy loss: - Experimental program just started Next step: Fix partonic EOS !

21. RNM meeting FIAS, Frankfurt, 22 Feb 2006 Hadro  Chemistry  T ch = 163  4 MeV,  b = 24  4 MeV  In central collisions: no need for  S !  Resonances do not fit: Hadronic life ! White papers: STAR: Nucl. Phys. A757, p102; PHENIX: p184 (2005).

22. RNM meeting FIAS, Frankfurt, 22 Feb 2006 21 Elementary p+p Collisions  Low multiplicities  use canonical ensemble: Strangeness locally conserved!  particle yields are well reproduced  Strangeness not equilibrated ! (  s = 0.5) Statistical Model Fit: F. Becattini and U. Heinz, Z. Phys. C 76, 269 (1997).

23. RNM meeting FIAS, Frankfurt, 22 Feb 2006 22 Pressure, Flow, … Thermodynamic identity  – entropy p – pressure U – energy V – volume  = k B T, thermal energy per dof In A+A collisions, interactions among constituents and density distribution lead to: pressure gradient  collective flow  number of degrees of freedom (dof)  Equation of State (EOS)  cumulative – partonic + hadronic

24. RNM meeting FIAS, Frankfurt, 22 Feb 2006 23 Momentum Distributions* 2 ] [(GeV/ 2 c) -1 dy dp N d T   K (dE/dx) p  K (kink) *Au+Au @130 GeV, STAR T th =107±8 [MeV] =0.55±0.08 [c] n=0.65±0.09  2 /dof=106/90 solid lines: fit range Two-parameter fit describes yields of , K, p,  T th = 90  10 MeV = 0.55  0.08 c  Disentangle collective motion from thermal random walk  K (dE/dx) p  K (kink)

25. RNM meeting FIAS, Frankfurt, 22 Feb 2006 24 Kinetic Freeze-out at RHIC 1) ,K and p change smoothly from peripheral to central collisions. 2) At the most central collisions, reaches 0.6c. 3) Multi-strange particles ,  are found at higher T and lower  Sensitive to early partonic stage!  What about v 2 ? 4) Single sudden freeze-out*:  all collectivity from partonic stage! STAR: NPA715, 458c(03); PRL 92, 112301(04); 92, 182301(04). *A. Baran, W. Broniowski and W. Florkowski; nucl-th/0305075.

26. RNM meeting FIAS, Frankfurt, 22 Feb 2006 25 Anisotropy Parameter v 2 y x pypy pxpx coordinate-space-anisotropy  momentum-space-anisotropy Initial/final conditions, EoS, degrees of freedom

27. RNM meeting FIAS, Frankfurt, 22 Feb 2006 26 v 2 in the Low-p T Region P. Huovinen, private communications, 2004 - Minimum bias data! At low p T, model result fits mass hierarchy well! - Details do not work, need more flow in the model!

28. RNM meeting FIAS, Frankfurt, 22 Feb 2006 27 Collectivity, Deconfinement at RHIC - v 2, spectra of light hadrons and multi-strange hadrons - scaling with the number of constituent quarks At RHIC, I believe we have:  Partonic Collectivity êDeconfinement  Thermalization ? PHENIX: PRL91, 182301(03) STAR: PRL92, 052302(04), PRL95, 122301(05). S. Voloshin, NPA715, 379(03) Models: Greco et al, PRC68, 034904(03) X. Dong, et al., Phys. Lett. B597, 328(04).

29. RNM meeting FIAS, Frankfurt, 22 Feb 2006 28 v 2 of Multi-strange Hadrons Strange-quark flow  partonic collectivity at RHIC! QM05 conference: M. Oldenburg; nucl-ex/0510026.

30. RNM meeting FIAS, Frankfurt, 22 Feb 2006 29   meson Flow at RHIC QM05 conference: M. Oldenburg; nucl-ex/0510026. Strange-quark flow  partonic collectivity at RHIC!

31. RNM meeting FIAS, Frankfurt, 22 Feb 2006 30 RQMD results, absolute numbers too low  need partonic flow ! However: 1) At low p T region: hydro-type mass ordering 2) Intermediate p T : baryon/meson ordering 3) Hadronic vacuum X-sections! 4) The number of constituent quark scaling may not be unique! Y. Lu et al., nucl-th/0602009. Hadronic Transport Model

32. RNM meeting FIAS, Frankfurt, 22 Feb 2006 31 Partonic Collectivity at RHIC 1) Copiously produced hadrons freeze-out ,K,p: T fo = 100 MeV,  T = 0.6 (c) >  T (SPS) 2) Multi-strange hadrons freeze-out: T fo = 160-170 MeV (~ T ch ),  T = 0.4 (c) 3) Multi-strange v 2 : Multi-strange hadrons ,  and  do flow! 4) Constituent Quark scaling: Seems to work for v 2 and R AA (R CP ) Deconfinement & Partonic (u,d,s) Collectivity !

33. RNM meeting FIAS, Frankfurt, 22 Feb 2006 32 Heavy-Flavor Quarks Plot: B. Mueller, nucl-th/0404015.  Symmetry is broken:  QCD dynamical mass  EW Higgs mass  Even in a QGP, charm and beauty quark-mass heavy !  If heavy quarks flow:  frequent interactions among all quarks  light quarks (u,d,s) likely to be thermalized Plot: B. Mueller, nucl-th/0404015. Mass (MeV/c 2 ) 10 6 10 5 10 4 10 3 10 2 10 1

34. RNM meeting FIAS, Frankfurt, 22 Feb 2006 33 The key point is to determine Heavy-Flavor Collectivity D 0, D , D + s,  + C, J/ , …

35. RNM meeting FIAS, Frankfurt, 22 Feb 2006 34 Charm(Bottom)  e  Spectrum  Three independent analyses using different sub-detectors  σ cc = 1.4  0.2  0.4 mb PHENIX, Au+Au:  cc = 0.62  0.06  0.16 mb  Need direct open charm reconstruction ! (D 0  K +  ) EMC -- STAR preliminary STAR: PRL 94, 062301 (2005); PHENIX: PRL 94, 082301 (2005).

36. RNM meeting FIAS, Frankfurt, 22 Feb 2006 35 Non-photonic electron v 2 c (b)  e + X  Large syst. uncertainties due to large background  Experimental data do not agree at 2<p T (e)<5 GeV/c!  v 2 (e) favors non-zero v 2 (c) at p T (e)<2 GeV/c. V. Greco et al. PLB 595(2004)202 B. Zhang et al. nucl-th/0502056

37. RNM meeting FIAS, Frankfurt, 22 Feb 2006 36 J/  Enhancement at LHC  Statistical hadronization  strong centrality dependence of J\  yield at LHC (and RHIC?)  slope ~  cc  Need total charm yields !  Measure D 0, D ±,  c,  c  Probe deconfinement and thermalization Calculations:P. Braun Munzinger, K. Redlich, and J. Stachel, nucl-th/0304013.

38. RNM meeting FIAS, Frankfurt, 22 Feb 2006 37 J/  at RHIC P. Braun-Munzinger et al.  Yellow band: allowed range by open charm from STAR and PHENIX  Large uncertainty from open charm cross section !  Need precise open charm reference !

39. RNM meeting FIAS, Frankfurt, 22 Feb 2006 38 Chiral Doubling P. Braun-Munzinger et al. M. Novak, Int. J. Mod. Phys. A20 (2005) 229.  Assume chiral doubling in charm sector  Still large uncertainties  Need precise open charm reference !  Direct open charm reconstruction

40. RNM meeting FIAS, Frankfurt, 22 Feb 2006 39  D  Meson Pair Correlations Pythia Calcs.: H. Woehri, priv. comm. Hadronic Transport Model: E.L. Bratkovskaya et al., PRC 71 (2005) 044901.  ccbar pair production: DDbar pairs are correlated !  Here:  correlation  If charm equilibrates  correlations vanish !  Influence of hadronic scattering (small) ?

41. RNM meeting FIAS, Frankfurt, 22 Feb 2006 40 Summary  Intermediate/high-p T : partonic energy loss  Elliptic flow of multi-strange hadrons  : partonic collectivity  Colored medium created at RHIC !  Status of Thermalization ?  Measure elliptic flow, spectra and yields of D 0, D , D + s,   C, J/ 

42. RNM meeting FIAS, Frankfurt, 22 Feb 2006 41 STAR MRPC - TOF STAR MicroVertex Tracker Active pixel sensors (APS) Two layers of thin silicon - Full open charm measurements - Full resonance measurements with both hadron and lepton decays STAR Upgrades