1. Heavy flavor production at RHIC Yonsei Univ. Y. Kwon

2. Contents Contents Introduction Introduction Current measurements Current measurements – Total cross sections by PHENIX and STAR – Related differential cross sections – R AA, flow, and further results – Charm/Bottom ratio How do we obtain the result? How do we obtain the result? – Direct reconstruction – Non-photonic e & prompt  Results at higher energy Results at higher energy A question? A question?

3. 3 Introduction : heavy quarks as a probe p+p : pQCD test baseline for A+A A+A : flow  thermalization high p T suppression  energy loss parton medium light ENERGY LOSS

4. Direct: reconstruction of all decay products Indirect: charm and beauty via electrons c  e + + anything (B.R.: 9.6%) b  e + + anything (B.R.: 10.9%) issue of photonic background charm (and beauty) via muons c   + + anything (B.R.: 9.5%) Introduction : (open) heavy flavor measurement

5. Total cross sections,PHENIX vs STAR Binary scaling STAR results ~ 2 times larger than PHENIX

6. Forward prompt  - production (PHENIX) Forward prompt  - production (PHENIX) PPG057 : PRD76, 092992(2007)

7. Leptons from Heavy flavor, PHENIX Leptons from Heavy flavor, PHENIX PHENIX Preliminary PRL, 98, 172301 (2007) Systematically higher than FONLL calculation e yield shows binary scaling, high p T suppression in central Au+Au p+p 200GeV/c

8. 8 Leptons from heavy flavor, STAR Leptons from heavy flavor, STAR STAR Preliminary Combined fit of , D 0, low p T e Low p T muon constrains charm cross-section

9. c dominant b dominant Heavy quarks in p+p from e + e - at PHENIX Heavy quarks in p+p from e + e - at PHENIX

10. d+Au: no suppression expected slight enhancement expected (Cronin effect) Peripheral Au+Au: no suppression expected Semi-Central Au+Au: very little suppression expected STAR hadrons p T > 6 GeV/c Central Au+Au: less suppression expected ? R AA R AA Nuclear modification factor

11. Energy Loss? Energy Loss?

12. Elliptic flow v 2 – NPE from HF decays PHENIX RUN4 :PRL, 98, 172301 (2007)

13. How do we obtain the result? How do we obtain the result?

14. STAR Preliminary Direct D-meson reconstruction (STAR) D0D0 Phys. Rev. Lett. 94 (2005) No displaced vertex used

15. Non-photonic electrons Inclusive electrons = photonic + non-photonic electron Direct measurement : converter method Estimation based on other (PHENIX) measurement : Cocktail method Dominant background :  0 Dalitz decay,  conversion Mostly from heavy quark

16. Tracker Identifier Absorber Collision vertex range Collision Muon Hadron Absorber Symbols Detector  -measurement, sources 1 1 : Hadrons, interacting and absorbed (98%), 3 3 : Hadrons, penetrating and interacting (“stopped”) 4 4 : Hadrons, “punch-through”, 5 : Prompt ,”desired signal” 5 2 2 : Charged   /K's, “decaying into  ” before absorber (≤1%),

17. PRELIMINARY Generator ( Decay  + punch-through ) 1. Light hadron measurement by PHENIX central arm (y = 0) 2. Gaussian extrapolation in rapidity to muon arm acceptance (  = 2.5) 3. Simplified spectrometer geometry.   -measurement, Signal composition

18. Forward prompt  - production (PHENIX) Forward prompt  - production (PHENIX) PPG057 : PRD76, 092992(2007)

19. Leptons from heavy flavor, PHENIX PHENIX Preliminary PRL, 98, 172301 (2007) Systematically higher than FONLL calculation Integral e yield follows binary scaling, strong high p T suppression at central AuAu collisions p+p 200GeV/c

20. 20 Leptons from heavy flavor, STAR Leptons from heavy flavor, STAR STAR Preliminary Combined fit of , D 0, low p T e Low p T muon constrains charm cross-section

21. High p T electrons (EMC trigger) FONLL * 5  p+p spectra STAR high p T non-photonic electrons STAR Phys. Rev. Lett. 98 (2007) 192301

22. Bottom contribution to non-photonic e Data consistent with FONLL. (b  e)/(c  e+b  e)

23. Results at higher energy Results at higher energy

24. Differential charm cross section Differential charm cross section

25. Differential bottom cross section Differential bottom cross section

26. A question? A question? STAR high pT electrons? STAR high pT electrons? If it’s problem, normalization (efficiency)? If it’s problem, normalization (efficiency)? – Detector thickness must be varying a lot!