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Hunt for the QGP at RHIC

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. Outline. Introduction High-p T Suppression

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Hunt for the QGP at RHIC

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  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.

  2. Outline • Introduction • High-pT Suppression • Bulk properties:- Hadron abundances- Heavy-Flavor (c,b) Collectivity • Summary

  3. Quark Gluon Plasma Source: Michael Turner, National Geographic (1996) • Quark Gluon Plasma: • Deconfined and • thermalized state of quarks and gluons •  Study partonic EOS in high energy nuclear collisions(?) Probe thermalization using heavy-quarks

  4. Phase Diagram

  5. Au +Au @ 20, 62, 130, 200 GeV Cu + Cu @ 20, 62, 200 GeV d + Au @ 200 GeV p + p @ 200, 400 GeV

  6. STAR Au + Au Collisions at RHIC Peripheral Event (real-time Level 3)

  7. STAR Au + Au Collisions at RHIC Mid-Central Event (real-time Level 3)

  8. STAR Au + Au Collisions at RHIC Central Event (real-time Level 3)

  9. Au + Au sNN = 200 GeV (|| < 0.75) Collision Geometry, Flow z x 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

  10. Hadron spectra from RHICp+p and Au+Au collisions at 200 GeV White papers - STAR: Nucl. Phys. A757, p102;

  11. Use high pT as probe Probe the bulk response Partons lose energy in medium Response of medium to pressure Measure nuclear modification factor RAA Measure elliptic flow v2 Partonic energy loss dE/dx, gluon density Partonic equation of state EoS Two Different Ways to Probe Bulk I believe, they are all correlated: back-back, R_AA, v2,… Interactions !

  12. leading particle suppressed hadrons q q ? Partonic Energy Loss Dominant Process:Gluon Bremsstrahlung • Fast partons emits gluons  energy loss • Energy loss depends on color charge density • Measure E  color (~gluon) density in dense phase

  13. leading particle suppressed hadrons q q ? Observation of Jet Quenching After the initial hard-scattering, the parton interacts strongly with the dense medium in central Au+Au collisions

  14. Leading hadrons Medium Energy Loss and Equilibrium • Suppression at intermediate pT - caused by final state interactions • Energy loss leads to progressive equilibrium in Au+Au collisions

  15. Photon – Hadron Correlations* • First high-pT correlations ! • No background subtraction ! • Same-side: increasing contributions from g-jet events • Away-side: different suppression for di-jet vs g-jets  First step towards g-jet Detailed energy loss studies ! *STAR analysis: T. Dietel; nucl-ex/0510046.

  16. <Nbinary>/inelp+p (Nuclear Geometry) Nuclear Modification Factor Quantify deviations from expected behaviour in p+p collisions: • If no “effects”: • R < 1 in regime of soft physics • R = 1 at high-pT where hard scattering dominates Suppression ? • Is R < 1 at high-pT ?

  17. Initial or Final State? • Large Suppression in central Au + Au • Suppression is absent in d-Au collisions • Final state effect  Partonic energy loss

  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.

  19. Partonic Energy Loss at RHIC (1) Intermediate/high pT: spectra suppressed and ratios start to decrease at pT ~ 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 !

  20. Hadro - Chemistry White papers:STAR: Nucl. Phys. A757, p102;PHENIX: p184 (2005). • Tch= 163  4 MeV, mb = 24  4 MeV • In central collisions: no need for S! • Resonances do not fit: Hadronic life !

  21. Elementary p+p Collisions • Low multiplicities  use canonical ensemble:Strangeness locally conserved! • particle yields are well reproduced • Strangeness not equilibrated ! (gs = 0.5) Statistical Model Fit: F. Becattini and U. Heinz, Z. Phys. C 76, 269 (1997).

  22. Pressure, Flow, … • Thermodynamic identity • – entropy p – pressure U – energy V – volume t = kBT, thermal energy per dof • In A+A collisions, interactions among constituentsand density distribution lead to: pressure gradient  collective flow • number of degrees of freedom (dof) • Equation of State (EOS) • cumulative – partonic + hadronic

  23. Tth=107±8 [MeV] <bt>=0.55±0.08 [c] n=0.65±0.09 2/dof=106/90 ] c)-1 [(GeV/ solid lines: fit range dy N T dp d p 2 Momentum Distributions* p p • Two-parameter fit describes yields ofp, K, p, L • Tth = 90  10 MeV • <bt> = 0.55  0.08 c  Disentangle collective motion from thermal random walk K (dE/dx) K (kink) p K (dE/dx) K (kink) p L L 2 *Au+Au @130 GeV, STAR

  24. Kinetic Freeze-out at RHIC • p,K and p change smoothly from peripheral to central collisions. • At the most central collisions, <bT> reaches 0.6c. • Multi-strange particles f, W are found at higher T and lower <bT> • Sensitive to early partonic stage! • What about v2 ? 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.

  25. Anisotropy Parameter v2 coordinate-space-anisotropy  momentum-space-anisotropy y py px x Initial/final conditions, EoS, degrees of freedom

  26. v2 in the Low-pT Region P. Huovinen, private communications, 2004 • Minimum bias data! At low pT, model result fits mass hierarchy well! • - Details do not work, need more flow in the model!

  27. Collectivity, Deconfinement at RHIC - v2, spectra of light hadrons and multi-strange hadrons - scaling with the number of constituent quarks At RHIC, I believe we have:  Partonic Collectivity • Deconfinement  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).

  28. v2 of Multi-strange Hadrons Strange-quark flow - partonic collectivity at RHIC! QM05 conference: M. Oldenburg; nucl-ex/0510026.

  29.  - meson Flow at RHIC Strange-quark flow - partonic collectivity at RHIC! QM05 conference: M. Oldenburg; nucl-ex/0510026.

  30. Hadronic Transport Model RQMD results, absolute numbers too low need partonic flow ! However: 1) At low pT region: hydro-type mass ordering 2) Intermediate pT: 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.

  31. Partonic Collectivity at RHIC • 1) Copiously produced hadrons freeze-out p,K,p: • Tfo = 100 MeV, T = 0.6 (c) > T(SPS) • 2)Multi-strange hadrons freeze-out: • Tfo = 160-170 MeV (~ Tch), T = 0.4 (c) • 3)Multi-strange v2: • Multi-strange hadrons f,  and  do flow! • 4) Constituent Quark scaling: • Seems to work for v2 and RAA (RCP) • Deconfinement & • Partonic (u,d,s) Collectivity!

  32. Heavy-Flavor Quarks • 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 106 105 104 103 102 10 1 Mass (MeV/c2) Plot: B. Mueller, nucl-th/0404015. Plot: B. Mueller, nucl-th/0404015.

  33. The key point is to determine Heavy-Flavor Collectivity D0, D, D+s, L+C, J/y, …

  34. EMC -- STAR preliminary Charm(Bottom)  e - Spectrum • Three independent analyses using different sub-detectors • σcc = 1.4  0.2  0.4 mbPHENIX, Au+Au: scc=0.62  0.06 0.16 mb Need direct open charm reconstruction !(D0  K + p) STAR: PRL 94, 062301 (2005); PHENIX: PRL 94, 082301 (2005).

  35. V. Greco et al. PLB 595(2004)202 B. Zhang et al. nucl-th/0502056 Non-photonic electron v2 c (b)  e + X • Large syst. uncertainties due to large background • Experimental data do not agree at 2<pT(e)<5 GeV/c! • v2(e) favors non-zero v2(c) at pT(e)<2 GeV/c.

  36. J/y Enhancement at LHC • Statistical hadronization  strong centrality dependence of J\y yield at LHC (and RHIC?) • slope ~ scc Need total charm yields ! • Measure D0, D±, Lc, Xc • Probe deconfinement and thermalization Calculations:P. Braun Munzinger, K. Redlich,and J. Stachel, nucl-th/0304013.

  37. J/y at RHIC • Yellow band: allowed range by open charmfrom STAR and PHENIX • Large uncertainty from open charm cross section ! • Need precise open charm reference ! P. Braun-Munzinger et al.

  38. Chiral Doubling • Assume chiral doubling in charm sector • Still large uncertainties • Need precise open charm reference ! • Direct open charm reconstruction P. Braun-Munzinger et al.M. Novak, Int. J. Mod. Phys. A20 (2005) 229.

  39. Df D - Meson Pair Correlations • ccbar pair production: DDbar pairs are correlated ! • Here: Df correlation • If charm equilibrates  correlations vanish ! • Influence of hadronic scattering (small) ? Pythia Calcs.: H. Woehri, priv. comm. Hadronic Transport Model:E.L. Bratkovskaya et al., PRC 71 (2005) 044901.

  40. Summary • Intermediate/high-pT: partonic energy loss • Elliptic flow of multi-strange hadrons f, W:partonic collectivity Colored medium created at RHIC ! • Status of Thermalization ? • Measure elliptic flow, spectra and yields ofD0, D, D+s, L+C, J/y

  41. STAR Upgrades 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

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