1. Charm hadron production at RHIC in combination model Motivation Quark combination model Results and discussions Summary 2008-9-20 JiNan China Tao Yao, Wei Zhou, Qu-Bing Xie School of Physics, Shandong University

2. One of the hot topics of both theory and experiment. ＊ many theory papers: the charm flow, energy loss, production etc. ＊ PHENIX and STAR collaborations have made many measurements. ◆ the binary scaling of ; STAR gives ~2 times bigger than PHENIX ! Two key ratios: ; The effects on charm hadron ratios from the baryon and strangeness enhancements are studied and predictions for RHIC and LHC are given. Important to accurately measure in future. The hadronization mechanism can be tested at RHIC and LHC. I. Motivation baryon enhancement coalescence mechanism charm baryon enhancement different charm hadron ratios different, effects on ？ The two ratios used in AA are now from reactions or annihilations

3. II. Quark Combination Model (QCM) in AA Nearest in rapidity axis Collinear Decay PYTHIA6.4 F.L.Shao et al. P. R. C71, 044903, 2005 ; P. R.C75,034904,2007. Rapidity and distribution Final hadrons

4. 130 GeV: =0.75 mb, =41 mb, =965 (0-5%), 18 62.4 GeV: =0.285mb, =36 mb, =904.3(0-5%), 7 5.5 TeV: =20 mb, =60 mb, =1303(0-10%), 343 The number of pairs, as input in the QCM, is given by The spectrum of charm quark at 200 GeV is inputted as a normalized form 200 GeV STAR: =1.4 mb, =42 mb, =1051(0-5%), 35 PHENIX: =0.622 mb, 16 III. Results and discussions

5. Fig.1. The invariant spectra at 200 GeV for meson, inclusive electron, non-photonic electron and muon. The solid (dashed) line are from the by the STAR (PHENIX) coll. A. dependencies of charm baryon to meson ratios and ordering

6. Fig. 2. The dependence for the ratios of charm baryons to mesons at 200 GeV The charm baryon enhancement is very prominent. The shapes are dependent on the CO/RE mechanism, decay effect and the charm quark spectrum All peaks broaden and shift right essentially because the spectrum of charm quark is much harder than that of u(d) quark A very similar of nonphotonic muon to that of nonphotonic electron

7. The ordering with strangeness content for strange hadrons has been observed at RHIC Nucl.Phys.A774:657-660,2006. STAR The effect should also be manifested by the strange charm hadrons. A powerful signal to prove the CO/RE hadronization mechanism for open charm hadrons.

8. ~67.7% ~100% ~32.3% 1.Strangeness enhancement 2. Branching ratios 3. Default But is used by PHENIX if B. The ratios in AA collisions at 200 GeV

9. Assuming and PHENIX has, whereas we have ~12% enhancement of ! The newest branching ratio for from PDGlive, give ~17% enhancement of ! (2) is

10. ~67.7% ~32.3% 1. the parameter dependence C. Parameter dependences of the ratios

11. charm decuplet baryons charm octet baryons ~ 100 % 2. the parameter dependence: almost independent 3. the parameter dependence independent of !

12. 4. the parameter dependence Note that the net baryon number or the u(d) quark number decreases with increasing: a. b. c. d. decrease with decreases (increases) for the net baryon number decreases. are independent of and are also independent of the net baryon number.

13. Fig.3. The data and solid line are the same as Fig. 1, but the dashed line is from the input, the solid line is from. Important for us to study their centrality dependence neglecting the differences of radial flows Important to study these ratios at various energies without the quark spectra being well determined 5. the c quark spectrum dependence: insensitive

14. Fig. 4. The centrality dependence for rapidity density of charm hadrons at 200 GeV ＋ ＋ consistent qualitatively with that of the Statistic Hadronization Model: P. L. B 571, 36 (2003) D. the centrality dependence yield of single-charm hadron

15. D. The centrality dependence of the ratios They are all independent of the centrality or ! Then within coalescence/recombination framework Assuming parameters are independent of the centrality

16. Note that Eq. (3) is still valid at different energy ! Important for us to study the ratios at different energy, especially at LHC energy for large uncertainty of ! E. The energy dependence of the ratios QCM the coalescence/ recombination mechanism the parameters, hadronization mechanism universal in AA the strangeness suppression factor the net baryon number factors vary with energy ratios variance with energy = 0.52, 0.48, 0.48, 0.48 = 0.859, 0.915, 0.927, 0.986(0.995) 62.4, 130, 200 GeV RHIC 5500 GeV LHC Predictions for RHIC and LHC in Table ITable I

17. The predictions of dependencies for the charm ratios, and are given. The charm baryon enhancement in intermediate range, similar to that of ratio, is very prominent. ordering with strangeness content for charm hadrons are discussed. The ratios in AA collisions are apparently different from those in reactions or annihilations due to the charm baryon enhancement and the strangeness enhancement, along with the newest decay data from PDG, the measured by PHENIX will become larger up to ~17%. The dependencies on energy, centrality and various parameters are studied. Predictions of charm hadron ratios for the upgrade of RHIC and for LHC are given. They are important for precise measurement of in future and the hadronization mechanism for open charm hadrons can be tested. Summary Thank you all ! Details in arXiv: 0809.0049

18. Back up

19. Zhangbu Xu J.Phys.G32:S309-S316,2006

20. The invariant spectra for SU(3) mesons (left panel) and baryons (right panel) in top centrality at 200GeV.

21. The invariant spectra for proton(left panel) and pion (right panel) at different centrality classes at 200 GeV

23. The invariant spectra for inclusive and non-photonic electron at 130 GeV