1. Heavy Quark Probes of QCD Matter at RHIC Huan Zhong Huang University of California at Los Angeles ICHEP-2004 Beijing, 2004

2. Outline 1) Experimental Evidences for Bulk Matter Hadronization 2) Recombination for Heavy Quark Mesons 3) Future Measurements of Heavy Quark Production Features at RHIC

3. Too Many Baryons at Intermediate p T

4. Baryon Production from pQCD  K K p p  e + e -  jet fragmentation from SLD Normal Fragmentation Cannot Produce the Large Baryon Yield

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

6. Particle Dependence of R CP suppression

7. STAR PHENIX Particle Dependence of v 2 Baryon Meson Why saturation at intermediate p T ? Why baryon and meson difference ?

8. Salient Features at Inermediate p T 1)Why so many baryons versus mesons? 2)Why does elliptic v 2 versus p T saturate ? 3)Why R cp and v 2 in two groups: Baryon and Meson ? Hadronization from bulk partonic matter – Constituent quark degrees of freedom Recombination/Coalescence scheme for hadron formation Surface emission

9. Constituent Quark Degree of Freedom K S – two quark coalescence  – three quark coalescence from the partonic matter surface?! Particle v 2 may be related to quark matter anisotropy !! p T < 1 GeV/c may be affected by hydrodynamic flow ! Hadronization Scheme for Bulk Partonic Matter: 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)

10. Quark Cluster Formation from Strongly Interacting Partonic Matter Volcanic mediate p T – Spatter (clumps)   Strangeness enhancement from QGP is most prominent in the region where particle formation from quark coalescence is dominant !

11. Multi-Parton Dynamics for Bulk Matter Hadronization Essential difference: Traditional fragmentation  particle properties mostly determined by the leading quark ! Emerging picture from RHIC data (R AA /R CP and v 2 )  all constituent quarks are almost equally important in determining particle properties ! v 2 of hadron comes from v 2 of all constituent quarks ! Are constituent quarks the effective degrees of freedom for bulk partonic matter hadronization ? How do we establish signatures for multi-parton dynamics, recombination model for example, where thermal constituent quarks or shower partons from jet production are both possible ?

12. Fragmentation vs Recombination Fragmentation Function  z = p hadron /p parton < 1 Recombination Scheme  p hadron = p parton-1 + p parton-2 …  Z >= 1

13. Fragmentation Functions from e+e Collisions Belle Data

14. Charm Mesons from Hadronic Collisions Charm meson p T ~ follow the NLO charm quark p T -- add k T kick -- harder fragmentation (  func or recombination scheme)

15. k T Kick? What about k L ? The x F distribution matches the NLO charm quark x F !

16. The RHIC D meson p T ~ NLO charm quark too NLO pQCD predictions are provided by R. Vogt, hep-ph/0203151 STAR Preliminary But NLO QCD calculation fits CDF data within a factor of 2 Recombination mechanism for D formation ?!

17. Recombination  D S /D 0 PYTHIA Prediction Charm quark recombines with a light (u,d,s) quark from a strangeness equilibrated partonic matter  D S /D 0 ~ 0.4-0.5 at intermediate p T !!!

18. p T Scales and Physical Processes R CP Three P T Regions: -- Fragmentation -- multi-parton dynamics (recombination or coalescence or …) -- Hydrodynamics (constituent quarks ? parton dynamics from gluons to constituent quarks? ) P T scale for heavy quarks?

19. Summary Formation of Dense Matter Partonic Degrees of Freedom Important Hadronization of Bulk Partonic Matter Heavy Quark Measurement One of the Key Future Critical Test of Multi-parton Dynamics for Hadronization Signature for Deconfinement !

20. The End

21. Two Particle Jet-like Correlations Jet-like two particle correlations (e.g., trigger particle 4-6 GeV/c, associated particle 2-4 GeV/c) : These correlations cannot be easily explained in terms of recombination/coalescence scenario ! But 1) the effect of resonances on the two particle correlations has not be adequately addressed 2) trigger biases – with two high p T particles the initial parton is considerably harder than if only one high p T particle is produced. Fragmentation region p T > 5.5 GeV/c 3) low level two particle correlations in the soft region can be accommodated in recombination/coalescence (wave induced correlation?)

22. Heavy Quark in QCD Medium Heavy Quark energy loss in color medium ! -- dead cone effect (less than light quarks) Charm enhancement from high temperature gluonic matter (T init > 500 MeV)! An Intriguing Scenario ?! PTPT R AA 1.0 Light hadrons Open Charm (p T scale) Require direct open charm measurement !

23. Geometry of Nucleus-Nucleus Collisions N part – No of participant nucleons N binary – No of binary nucleon-nucleon collisions cannot be directly measured at RHIC estimated from Woods-Saxon geometry

24. A Critical Test for Recombination Duke Group, PLB 587, 73 (2004) p T Scale !!   And Strange Quark Dynamics in Bulk Matter STAR will make a measurement of  and  v 2 from run-4 Au+Au data !

25. Elliptic Flow Parameter v 2 y x pypy pxpx coordinate-space-anisotropy  momentum-space-anisotropy Initial/final conditions, dof, EOS

26. The Field & Feynman picture of cascade fragmentation Kretzer@ISMD04

27. Charm and Bulk Matter Does Charm Flow? Thermalization of partonic matter -- charm elliptic flow v 2 ! -- charm hadron chemistry ! Simulation by X. Dong Charm Meson v 2 has to come from light quark v 2 and possibly charm quark v 2 !