1. 1 STAR Open Heavy Flavor Measurements Gang Wang (UCLA) 1  Motivation  D 0 / D s / D*  Non-photonic electron  Summary

2. 2 Why heavy quarks? X. Zhu, et al, Phys. Lett. B647, 366(2007). - Higgs mass: electro-weak symmetry breaking (current quark mass). - QCD mass: Chiral symmetry breaking (constituent quark mass).  Strong interactions do not affect heavy-quark mass.  Initial fusion dominates heavy flavor production.  Study properties of the hot and dense medium at the early stage of heavy-ion collisions.  Light flavor thermalization. M. Gyulassy & Z. Lin, PRC 51 (1995) 2177 Charm quark

3. The STAR detector and Particle ID Large acceptance |  | < 1, 0 <  < 2   p   TPC dE/dx, momentum  TOF 1/  difference Run9 ~ 72% of full TOF Run10: 100% significantly improved PID for final state hadrons, especially for kaons 3

4. 4 Previous D 0 measurements STAR Preliminary ArXiv: 0805.0364 run4 D0D0 PRL. 94 (2005) 62301 run3

5. 5 N bin scaling  Charm x-section ~ Nbin. STAR Preliminary ArXiv: 0805.0364 run4 run3 NPE+D 0 NPE+μ+D 0 NPE+μ Difficulties:  Short life time  Low production rate  Large combinatorial bg

6. D 0 in 200GeV p+p Mass window: 1.72 – 2.1 GeV/c 2 ~ 4  signal observed. Yifei Zhang, DNP2010 talk 0.4 < p T < 2.2 GeV/c Mixing event Track rotation Same sign run9

7. 7 D s in 200GeV Au+Au Preliminary results indicate statistical hadronization. Assume p T spectrum shape similar to D 0 : 47% yield covered. D ± yields estimated from D ± /D 0 ratio from e+e- data. with the help of Silicon Vertex Tracker. Sarah LaPointe, WWND2010 talk I.Kuznetsova, J. Rafelski, Eur. Phys. J. C 51 1 (2007) 113-133 run7

8. 8 D* in 200GeV p+p Background combinations: Wrong sign: D 0 and  -, D 0 bar and  + Side band: 1.72< M(K  ) < 1.80 or 1.92 < M(K  ) < 2.0 GeV/c 2 All triggers included. More than 4  signal at low p T and very significant at high p T - mostly from EMC-based high neutral energy triggers. Yifei Zhang, DNP2010 talk run4

9. D* in 200GeV p+p All triggers included. More than 4  signal at low p T and very significant at high p T - mostly from EMC- based high neutral energy triggers. Wrong sign and side-band method reproduce background well. STAR Preliminary No significant charge asymmetry Yifei Zhang, DNP2010 talk 9

10. Summary: D mesons  Previous STAR NPE/μ/D 0 measurents in Au+Au and d+Au show the N bin scaling of charm x-section.  STAR D s measurement in Au+Au tends to support the statistical hadronization model.  Open charm hadrons are reconstructed from STAR run9 p+p 200 GeV data.  4  D 0 signal at low p T and more significant D* signal at high p T are observed.  Working on efficiency for p T spectra and cross- section. 10

11. Photon conversions    →   → e + e - in material  Dalitz decays    →  e + e - Heavy flavor electrons D/B → e ± + X  Weak Kaon decays K e3 : K ± →   e ± e 1 GeV/c  Vector Meson Decays  J  → e + e - < 15% contribution in all p T Photonic electron Non-photonic electron Electron signal and background 11

12. 12 Long and slowly dying issue on RHIC NPE 12 Results differ by a factor of two in p T spectra Total cross section p+p collisions Au+Au collisions Investigation is underway STAR PRL 97(2007)192301 PHENIX PRL 98(2007)172301 PRL 94(2005)082301 PRL 97(2006)252002 STAR d+Au PRL 94(2005)62301 STAR run3

13. 13 STAR preliminary R(cm) Beam pipe + SVT + SSD+ Dalitz Beam pipe + Dalitz TPC Inner Field cage Count STAR efforts Significantly Increase the S/B of this analysis (2008-present) Cross check NPE measurements with early runs. Yield of conversion electrons at different radial location 13 Wei Xie, HP2010 talk

14. 14 STAR high p T NPE in 200GeV p+p Measurement done using TPC+EMC using run08 and run05 data. p T >2.5GeV/c NPE measurement with dramatically different background agree with each other very well Combined using “ Best Linear Unbiased Estimate”. χ 2 /ndf = 4.81/7 = 0.69 14 Wei Xie, HP2010 talk

15. 15 Comparison with the Published NPE Results STAR and PHENIX NPE result in 200GeV p+p collisions consistent within errors at p T > 2.5 GeV/c STAR High p T NPE results are consistent with FONLL in 200GeV p+p collisions 15 Wei Xie, HP2010 talk See Wenqin Xu's talk for details on e B x-section!

16. Away Side in medium : How does B/D lose energy? Via conical emission? Conical Pattern in Conical Pattern in 2-Particle Correlations in Au+Au Collisions p T trig = 3-4.0 GeV/c; p T asso = 0.5-1 GeV/c Motivations Near Side: what ’ s the contribution of B/D decay to the non- photonic electrons? trigger What if we trigger on non-photonic electrons? 16

17. Study of heavy flavor via non-photonic electrons D mesons have their directions well represented by the daughter electrons, above 1.5 GeV/c. Electrons from B decays can represent the B meson momentum direction well if p T > 3 GeV/c. PYTHIA 17

18. 18 Disentangle Charm and Bottom Production Wider  φ distribution for B meson because of the larger mass. Combined fit on data to obtain the B meson contribution to non- photonic electron. B D hep-ph/0602067

19. 19  ~30-60% of non-photonic electron come from B meson in 200GeV p+p collisions.  Assume the same fraction in Au+Au collisions, results indicate B meson is suppressed 19 B Meson Suppression in 200 GeV Au+Au See Andre Mischke's talk for details! Phys. Rev. Lett. 105 (2010) 202301 run5&6

20. 20  Raw NPE-h correlation without pile-up removal in 500GeV p+p collisions.  PYTHIA simulation still shows different near-side peaks for NPE from D and B. 20 NPE-h Correlation in 500 GeV p+p Wei Li (ATHIC2010 talk) run9

21. 21 CuCu AuAu 21.7 / 5 34.4 / 5 21 B. Biritz (QM2009) Away side broadened, beyond PYHTIA fit, in both the Au+Au and the Cu+Cu collisions Broadened Awayside in the NPE-h Correlations 0 – 20%: 3 < p T trig < 6 GeV/c & 0.15 < p T asso < 0.5 GeV/c run5 run7

22. 22 Non-photonic e-h correlations in d+Au 200 GeV The away-side correlation can be well described by PYTHIA calculations for p+p. No medium effects seen here. 3 < p T trig < 6 GeV/c & 0.15 < p T asso < 0.5 GeV/c Gang Wang, HP2010 talk run8

23. 23 Above 1.5 GeV/c, D-decay electrons well represent the mother D mesons ’ direction. e D v 2 ~ D v 2 Similarly, above 3 GeV/c, e B v 2 ~ B v 2 Partonic flow picture is supported for u, d, s. What about heavier quarks? Motivations PHENIX, arXiv:nucl-ex/0604011; STAR, Nucl. Phys. A 830(2009)19c.

24. NPE v 2 Non-photonic e v 2 is lower than hadron v 2 (or K S 0, Λ). STAR, Phys. Rev. C 77 (2008) 54901 Gang Wang, HP2010 talk 24 run7

25. Summary: NPE  Discrepancy in high p T NPE has been solved!  NPE-h correlations have been measured in p+p collisions to retrieve B and D contributions, and used to study B energy loss.  Using d+Au as a reference, the shape of NPE-h correlation on the away-side is found to be modified in central Cu+Cu and Au+Au collisions due to the presence of the dense medium created in these collisions.  NPE v 2 values obtained via fitting the correlations fall in a reasonable range, and are lower than hadron(or K S 0, Λ) v 2.  Correlations with heavy flavor tag: jet reconstruction, ridge.. 25

26. 26 Future of Heavy Flavor Measurement at STAR MTD (MRPC) See Xin Dong's talk for details!

27. 27 backup 27

28. 28 Disentangle Charm and Bottom Production Near side: mostly from B mesons Away side: charm (~75%), Bottom (~25%) STAR preliminary JPG35(2008)104117

29. K* in 200GeV p+p Three different methods to reproduce combinatorial background. Very good K* 0 and K 2 *(1430) signal observed. K* 0 K 2 *(1430) Run 9 p+p 200 GeV 105M minbias events Yifei Zhang, DNP2010 talk 0.4 < p T < 2.2 GeV/c

30. 30 Energy loss mechanisms of non-photonic Electrons D0D0 radiative energy loss c quark K+K+ l e-/-e-/- light (D. kharzeev, M.Djordjevic et al. ) u c “dead cone effect”: gluon radiation suppressed at  < m Q /E Q collision energy loss c quark Hot/Dense Medium (Teany, Ralf, Denes et al.) D0D0 K+K+ l e-/-e-/- D0D0 meson energy loss c quark u c Hot/Dense Medium Ivan, et al u c D0D0 K+K+ l e-/-e-/- 30 Wei Xie, HP2010 talk