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Recent Results on Properties of QCD Matter at RHIC

Recent Results on Properties of QCD Matter at RHIC. Huan Zhong Huang 黄焕中 Department of Physics and Astronomy University of California Los Angeles, CA 90095-1547 ATHIC-2010 IOPP/CCNU Wuhan. Thanks to Jinhui Chen, Shusu Shi, Gang Wang, Wenqin Xu and Nu Xu.

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Recent Results on Properties of QCD Matter at RHIC

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  1. Recent Results on Properties of QCD Matter at RHIC Huan Zhong Huang 黄焕中 Department of Physics and Astronomy University of California Los Angeles, CA 90095-1547 ATHIC-2010 IOPP/CCNU Wuhan Thanks to Jinhui Chen, Shusu Shi, Gang Wang, Wenqin Xu and Nu Xu

  2. STAR:A Typical Collider Detector Tracking: TPC Particle ID: TOF Electromagnetic Calorimetry: BEMC+EEMC+FMS (-1 ≤  ≤ 4) Upgrades: Muon Telescope Detector Roman Pots Phase 2 Forward Upgrade Heavy Flavor Tracker (2013) Forward Gem Tracker (2011) Full azimuthal particle identification over a broad range in pseudo-rapidity

  3. STAR Detector in 2014 MTD EMC Barrel MRPC ToF Barrel EMC End Cap FMS BBC FPD Roman Pots Phase 2 TPC computing DAQ1000 COMPLETE Trigger and DAQ Upgrades FGT HFT Ongoing R&D

  4. Detector and Physics Capability Heavy Flavor Tracker: 10’s mm position resolution D0 ct=123 mm; B0 ct=456 mm Time-Projection Chamber: mm position resolution Large acceptance – charged particles KS ct=2.7 cm; W ct=2.5 cm Time-of-Flight: <100 pico-second timing resolution K-p separation 1.8 GeV/c p-K separation 3.0 GeV/c Electromagnetic Calorimeter: 16-18%/sqrt(E/GeV) photons and electrons (Jet Energy) Shower Max Detector – Electron ID Muon Telescope Detector: MuonIdentification (Upsilon states)

  5. Quark-Hadron Phase Transition 5

  6. Volcanic high pT -- Strombolian eruption Volcanic mediate pT – Spatter (clumps) Volcanic low pT – Bulk matter flows Nucleus-Nucleus Collisions and Volcanic Eruption • Initial Temperature • Parton Energy Loss • Bulk Matter Hadronization • Bulk Properties -- Viscosity

  7. Modern Technology can Measure Temperature Well Stable Objects – Long Measurement Time ! T=2.725 +- 0.001 K

  8. Nuclear Collisions – a Flash in 10-23 seconds! Huge Stretch Transverse Expansion High Temperature (?!) Nuclei pass thru each other < 1 fm/c Thin Pancakes Lorentz g=100 The Last Epoch: Final Freezeout-- Large Volume Au+Au Head-on Collisions  40x1012eV ~ 6 micro-Joule Human Ear Sensitivity ~ 10-11 erg = 10-18 Joule A very loud Bang, indeed, if E Sound…… Not easy to measure thermal radiations --- overwhelming photons are from p0 decays !

  9. Extract Thermal Radiation from Virtual g* (di-electrons) Yield Direct g*/inclusive g*from fitting the following function: r = direct g*/inclusive g* • Fit in 120-300MeV/c2(insensitive to p0 yield) • The mass spectrum follows the expectation for m > 300 MeV •  S(m) = dNg*/dNg~ 1 9 A. Adare et al., PRL 104, 132301 (2010)

  10. The Partonic Matter at RHIC is very Hot initially (T>300 MeV) exp + TAA scaled pp • Direct photon measurements • real (pT>4GeV) • virtual (1<pT<5GeV) • p+p data consistent withpQCDdown to pT=1GeV/c • Au+Au data require source otherthanpQCD for pT < 2.5 GeV/c • The source could be TAuAu = 221  19stat  19syst MeV (time averaged) • Theoretical calculations putTinit 300-600 MeV range. Fit to pp NLO pQCD (W. Vogelsang) 10

  11. Lattice QCD Calculations

  12. New Calculatiob of Dissociation Temperatures Agnes Mocsy and Peter Petreczky PRL 99, 211602 (2007) 1.2 <1.0 <1.0 2.0 1.3 1.2 A.Mocsy Significant Changes in Dissociation Temperatures ! Experimentally not demonstrated yet – See Zhuang’s Talk

  13. Hard Scattering and Jet Quenching leading particle suppressed back-to-back jets disappear Parton Energy Loss in A+A Hard Scattering in p+p Reduction of high pT particles Disappearance of back-to-back high pT particle correlations

  14. Nuclear Modification Factors Use number of binary nucleon-nucleon collisions to gauge the colliding parton flux: N-binary Scaling  RAA or RCP = 1 simple superposition of independent nucleon-nucleon collisions !

  15. RAA(pT>6GeV/c) Almost pT Independent RAA=(Au+Au)/[Nbinaryx(p+p)] Empirical Implications for a constant RAA for pT > 6 GeV/c !!

  16. Energy Loss Shifts pp pT to AA pT-DpT pp AA/Nbin DpT pT > 5 GeV/c For a power-law function (1+pT/a)-n a flat RAA DpT/pT constant ! What Physical Processes?

  17. Absence of Explicit Path Length Dependence The centrality dependence of DpT/pTcould be due to the initial energy density in collisions ! 17

  18. T. Hirano et al, Phys. Rev. C69, 034908 (2004) What Possible Physical Scenario for ELoss without L dependence ELoss of Partons: 1) Strong dependence on energy density 2) Rapid decrease of energy density in time interval < traversing time Hydrodynamic models show such a scenario plausible !

  19. V2 and RAA are Related via Path Length Dependence Precise value of v2 at pT> 6, 10 GeV/c ? RAA at pT > 10 GeV/c at RHIC should RAA approach unity at higher pT ? Future measurements will shed lights on possible physical scenarios for parton energy loss dynamics ! Heavy Quarks will be special -- Lorentz g dependence on partonELoss on jet-medium interaction Mach cone formation? 19 Dec 2008 IOPP workshop

  20. New PHENIX Measurement on v2 and RAA PRL 105, 142301 (2010) Caution: Npart dependence is not the same as path length dependence !

  21. Another Perspective on the PHENIX Data eccentricity – initial shape of the participants (volume) What is the physics for v2 ~ eccentricity at high pT?

  22. Physics with Tagged Jets Jet-medium interactions to probe medium properties: quark jet and gluon jet – different color factors no unique tagging of quark or gluon jets no experimental evidence for color factors -- quark-gluon conversion process or -- failed to correctly tagging jets Use high pT non-photonic electrons to tag HQ jet non-photonic electrons: not from photon conversion or Dalitz decays -- virtual photon conversion mostly from semi-leptonic decays of Charm and Bottom mesons

  23. l Heavy Quark Production Mechanism K+ e-/- e-/- e+/+ J/y K- e+/+ l D0 • Sensitive to initial gluon density and gluon distribution • Sensitive to initial gluon density and gluon distribution • Energy loss when propagating through dense medium • Suppression or enhancement of charmonium in the medium is a critical signal for QGP. • Different scaling properties in central and forward region indicate shadowing, which can be due to CGC.

  24. Heavy Quarks Unique Heavy Quark Flavors (Charm or Beauty) Heavy Flavors once produced – do not change to light flavor easily heavy quark production can be calculated from pQCD approach more reliably than light quarks Trace heavy quark flavors in nuclear collisions -- collision dynamics and hadronization mechanism Fragmentation versus Recombination/Coalescence Fragmentation p(heavy quark meson)/p(heavy quark) < 1 Recombination/Coalescence p(heavy quark meson)/p(heavy quark) >= 1

  25. Physics in NPE-h correlations trigger Near Side: What’s the contribution of B/Ddecays to non-photonic electrons? Works for p+p ! Away Side: Heavy quark interaction with the QCD medium -- sQGP features?

  26. NPE-Hadron Angular Correlations e-h correlations from p+p collisions pT 2.5-3.5 GeV/c B D pT 5.5-6.5 GeV/c B D

  27. B Decay Contributions to NPE PHENIX 90% C.L. STAR Data 27

  28. A Constraint on C-B Eloss not a Measurement yet But even in extreme case, RAA for NPE from B decays < 0.6 at 90% CL – sizeable parton energy loss

  29. Non-photonic e-h correlations in d+Au 200 GeV 3 < pTtrig< 6 GeV/c & 0.15 < pTasso< 0.5 GeV/c STAR Preliminary Non-photonic e-h azimuthal correlation is measured in one π range, and open markers are reflections.The away-side correlation can be well described by PYTHIA calculations for p+p. No medium effectsseen here.

  30. Non-photonic e-h correlations in A+A 200 GeV CuCu AuAu 0 – 20%: 3 < pTtrig< 6 GeV/c & 0.15 < pTasso< 0.5 GeV/c B. Biritz, Nucl. Phys. A 830(2009)849c The broad structures on the away side are there for both Au+Au and Cu+Cu collisions. PYTHIA won’t fit.

  31. What physics is in the ridge? Ridge observation in high multiplicity p+p collisions!

  32. “Triggered” correlations P RC 80 (2009) 064912 3 < pT,trigger< 4 GeV/c pt,assoc. > 2 GeV/c • Near-side correlation structure: • Central Au+Au: cone-like + ridge-like • Ridge correlated with jet direction • Approximately independent of Dhand trigger pT

  33. STAR Observation in Non-triggered Events STAR – PRC 73 (2006) 64907 Au+Au 130 GeV Data central peripheral

  34. What Data Are Needed? We do not know exactly the physics behind the ridge ! -- medium interaction and ‘trigger’ bias -- jet-medium interaction -- parton-parton multiple interactions Lack of hard experimental evidence ! We need to see (or not see) ridge effect relating to high pT (pT> 5-6 GeV/c) or HQ tagged jets – current data (pT 3-4 GeV/c) inconclusive ! STAR should have the data on tape already.

  35. The Partonic Matter at RHIC Flows Hydrodynamically Ideal Hydrodynamics shear viscosity h = 0 Strongly Interacting Matter  h/s = shear viscosity/entropy Povtun, Son and Starinets PRL94 111601 (2005) quantum limit h/s =1/4p for N=4 supersymmetric Yang-Mills theory Is this limit universal? Great for string theorists! AdS/CFT calculations -- almost like QCD -- can be tested experimentally

  36. coordinate-space-anisotropy  momentum-space-anisotropy y py px x Initial/final conditions, dof, EOS Elliptic Flow Parameter v2 36

  37. Constituent Quark Scaling

  38. Volcanic mediate pT – Spatter (clumps) Hadronization of Bulk Partonic Matter  Coalescence Constituent Quark Number Scaling Partons at hadronization have a v2  Collectivity Deconfinement ! Quark Coalescence – (ALCOR-J.Zimanyi et al, AMPT-Lin et al, Rafelski+Danos, Molnar+Voloshin …..) Quark Recombination – (R.J. Fries et al, R. Hwa et al)

  39. Multi-Parton Dynamics for Bulk Matter Hadronization Essential Features: Traditional fragmentation  particle properties mostly determined by the leading quark ! Emerging picture from RHIC data (RAA/RCP and v2)  all constituent quarks are almost equally important in determining particle properties ! v2 of hadron comes from v2 of all constituent quarks ! The fact that in order to explain the v2 of hadrons individual constituent quarks (n=2-meson,3-baryon) must have a collective elliptic flow v2 and the hadron v2 is the sum of quark v2  Strong Evidence for Deconfiement ! 39

  40. Strangeness from Bulk Partonic Matter RCP X L Constituent Quark Number Scaling -- Hadronization through quark clustering -- Effective DOF – constituent quarks quasi-hadrons at Tc ? Lattice QCD picture? W f(ss) 40

  41. Parton PT Distributions at Hadronization If baryons of pT are mostly formed from coalescence of partons at pT/3 and mesons of pT are mostly formed from coalescence of partons at pT/2 • and f particles have no decay feeddown contribution ! • decay contribution is small These particles have small hadronic rescattering cross sections 41

  42. Strange and down quark distributions s distribution harder than d distribution perhaps related to different s and d quarks in partonic evolution Independent Test – f/s should be consistent with s quark distribution Yes ! 42 J.H. Chen et al., PRC78, 034907 (2008)

  43. Effective Parton Distribution in the Drop at Hadronization L Parton Spectroscopy at RHIC X W f Use particle emission to measure partonpT distribution and angular anisotropy (v2) in the dense parton drop !!

  44. Theoretical Approach from Resonance Recombination Model Min He, R. Fries and R. Rapp PRC 82, 034907 (2010) : Quark Coalescence to Resonance/Quasi-hadron Matter just Prior to Chemical Freeze-out Quark masses u/d 0.3; s 0.45; c 1.5 and b 4.5 GeV/c2 Hadronization equilibrated quark soup to resonance hadron gas  thermal statistical model

  45. QCD Bulk Properties Equation-of-State -- sensitive to the degrees of freedom -- hydrodynamic calculations Viscosity to entropy ratio (h/s) -- characterization of strongly interacting QGP -- connection to string theory techniques

  46. Extraction of h/s relies on viscous hydrodynamic calculations Assuming -- η/s does not depend on the collision centrality significantly. • Data: v2{FTPC} • Fit range: • 0.15 < pT < 1 GeV/c • Less dependence on the initial geometrical shapes • The shape change at pT>1 GeV/c is dominated by q-hat – parton energy loss STAR Preliminary AuAu@200 [1]K. Dusling, G. Moore and D. Teaney, arXiv:0909.0754

  47. Strongly Interacting Partonic Matter @RHIC--- almost perfect fluidity AuAu@200 STAR Preliminary Different exp method for v2 calculations • Less dependence on the initial geometrical shapes • η/s: (0.5~2)/(4π)

  48. Summary Central Au+Au Collisions at RHIC Bulk Partonic Matter -- 1) Initially very Hot T above 300 MeV 2) Parton energy loss and jet-medium interaction 3) parton collectivity v2 and hydro expansion Deconfined matter with parton DOF h/s small – near the limit 1/4p L X W

  49. Discoveries from Unexpected Areas?! RHIC -- Frontier for bulk partonic matter formation (quark clustering and rapid hadronization) -- Factory for exotic particles/phenomena Potential exotic particles/phenomena: tetra- penta-quark states (particle and anti-part) di-baryons H – (L-L, uuddss) [W-W] (ssssss) strange quark matter meta-stable Parity/CP odd vacuum bubbles disoriented chiral condensate …… 49

  50. Near Future Perspective Is there a critical point in the QCD phase diagram? -- RHIC low energy scan Initial conditions for partonic evolutions? -- Color Glass Condensate Heavy Quark flavored QGP -- detector upgrade for charm/bottom Flavor tagged parton energy loss in dense matter

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