1. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 1 Open charm production at RHIC Xin Dong University of Science and Technology of China - USTC

2. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 2 Outline  Introduction  Charm in elementary collisions  Open charm production in heavy ion collisions Total charm yields Charm quark Δ E in medium Charm quark v 2  Summary and outlook

3. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 3 What we have learned at RHIC p T (GeV/c) 0 ~2~6 Jet quenching pQCD at work, high density matter Hydro at work strong interactions collectivity NCQ grouping partonic d.o.f  Jet-quenching: high density medium created  Large v 2 and β T : partonic collectivity  NCQ-grouping: partonic collectivity and deconfinement To fix the partonic EOS, one must test the thermalization experimentally. Heavy flavor probe: Heavy flavor collectivity → light flavor thermalization Note: to test the bulk medium response, low p T region is relevant!

4. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 4 Why Charm? – an ideal probe for studying QGP B. Mueller, nucl-th/0404015 Heavy !  Charm quarks created at early stage of HIC  total yields scaled by N bin  Sensitive to the partonic rescatterings  Collectivity, flow  light flavor thermalization Charm as a probe to test early thermalization!

5. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 5 Charm energy loss Y. Dokshitzer & D. Kharzeev PLB 519(2001)199 Radiative energy loss of heavy quarks and light quarks --- Probe the medium property ! Heavy quark has less dE/dx due to suppression of small angle gluon radiation “Dead Cone” effect M. Djordjevic, et. al. PRL 94(2005)112301 B.W. Zhang et. al. PRL 93(2004)072301 N. Armesto et. al. PRD71(2005)054027 R. Rapp et. al. …… J. Adams et. al, PRL 91(2003)072304 h±h±

6. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 6 Charm elliptic flow V. Greco et al., PLB 595(2004)202 Coalescence approach Large cross section needed to reach high v 2 : Charm quark flows → Indication of light flavor thermal equilibrium! Is the large cross section realistic? AMPT transport model B. Zhang et al., nucl-th/0502056

7. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 7 The key point is to determine Charm collectivity

8. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 8 Charm measurements at RHIC central arms --- electrons: DC (tracker), Ring Image Cherenkov (RICH), EMCal for(back)ward muon arms --- muons: muon tracker, muon identifier D recon. from hadronic decay channels: TPC (+TOF) electrons: TPC, TPC+TOF, TPC+EMC Advantages: -- low material budget, clean environ. -- central, forward/backward coverage Advantages: -- reconstruction of D mesons -- large acceptance |φ|<2π,|  |<1.5

9. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 9 R. Vogt Int. J. Mod. Phys. E 12(2003)211 D mesons,  ’,  Large Q value needed (>≈3GeV)  powerful test for pQCD calculation Heavy flavor in pQCD PDF ccbar pQCD

10. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 10 Direct charm reconstruction STAR Preliminary STAR, PRL, 94, 062301 (2005) d+Au 200 GeV STAR: Mixed-event technique benefiting from large acceptance of the TPC A. Tai, QM04

11. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 11 Non-photonic electrons PHENIX: three methods to subtract the photonic background S. Kelly, QM04 STAR: three independent analysis using different sub-detectors EMC -- STAR preliminary σ cc = 1.4  0.2  0.4 mb STAR, PRL, 94, 062301 (2005) p+p 200 GeV

12. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 12 Issue I - total charm cross section 1)STAR > pQCD PHENIX >~ pQCD 2)Charm total cross section is a critical reference for J/ψ suppression/enhance ment determination. 3)Scales (μ F and μ R ) may be energy dependent. STAR, PRL, 94, 062301 (2005) R. Vogt, private communication

13. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 13 Spectrum coverage σ cc = 1.1  0.1  0.3 mb The reconstructed D measurement has much smaller systematic uncertainties in determining the total cross section. ~ 1.3 GeV/c 90% 15%

14. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 14 Issue II - p T spectrum  PYTHIA spectrum is steeper than data spectrum  beauty contamination: Typical pQCD calculations: Beauty will take over charm beyond ~4 GeV/c M. Cacciari et. al. hep-ph/0502203 PYTHIA curves from S. Kelly, QM04

15. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 15 Summary on charm in elementary collisions Open issues of charm production in elementary collisions:  Total charm cross section is higher than typical pQCD calculations!  Spectrum is harder than those from typical PYTHIA predictions!  Beauty contribution Precise measurements of reconstructed open charm in elementary collisions are definitely necessary!

16. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 16 Centrality dependence of non-photonic electrons in Au + Au PHENIX, PRL 94, 082301(2005) Centrality dependence of charm production is consistent with N bin scaling at 0.8<p T (e)<4.0 GeV/c!

17. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 17 d + Au  Au + Au STAR Highlight talk 1.13  0.09  0.42 mb in Au + Au 1.4  0.2  0.4 mb in d + Au Approximately N bin scaling from d+Au to Au+Au! As expected --- charm quarks are mostly created from initial NN interactions!

18. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 18 (3) q_hat = 14 GeV 2 /fm (2) q_hat = 4 GeV 2 /fm (1) q_hat = 0 GeV 2 /fm (4) dN g / dy = 1000 R AA of non-photonic electrons PHENIX Highlight talk  Both experiments agree!  Clear evidence of large heavy quark energy loss! STAR Highlight talk

19. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 19 Challenges to theoretical friends M. Djordjevic, et. al. nucl-th/0507019 N. Armesto et. al. private comm. Current energy loss mechanisms can only account for part of strong suppression of R AA for electrons. any beauty?

20. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 20 Charm quark collective motion  Electron spectra cannot disentangle different charm hadron shapes at low p T → Need precise measurement of reconstructed D at low p T (<~3GeV/c)! S. Batsouli, et al, Phys.Lett.B 557 (2003) 26 Electrons: Smearing in p T axis

21. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 21 V. Greco et al. PLB 595(2004)202 Non-photonic electron v 2  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. B. Zhang et al. nucl-th/0502056

22. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 22 Summary  Charm production cross section at 200 GeV measured in elementary collisions.  Total charm yields in HIC approximately obey N bin scaling.  v 2 (e) favors non-zero v 2 (c) !?  R AA (e) ≈ R AA (h) !? An exciting heavy flavor program has started at RHIC! Open Issues: pQCD description where is beauty? Heavy flavor collectivity! Light flavor thermalization! @RHIC If confirmed

23. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 23 Summary  Before any physics conclusion, experimental data must agree!  Single electron approaches are placeholder.  Identified open charm (beauty) measurements are definitely necessary.  The upgrade programs in PHENIX and STAR are essential! Electron approach experiences: 1) spectrum low p T : no distinguishing power high p T : beauty is largely uncertain 2) v 2 large statistical and systematical uncertainties

24. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 24 Upgrade detectors at PHENIX Barrel and Endcap Silicon Vertex Tracker  Direct charm/beauty reconstruction: low p T via e/μ, high p T via Kπ G. Kunde, WW 05

25. Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC 25 Upgrade detectors at STAR Full Barrel MRPC - TOF Heavy Flavor Tracker  Full open charm measurements - direct D-meson V0 reconstruction - spectrum, v 2 (low  high p T ), correlations … K. Schweda’s talk