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Open charm and charmonium production at RHIC

(1) Motivations (2) Results from STAR and PHENIX (3) Conclusions and outlook. Open charm and charmonium production at RHIC. An Tai. J/ y, D W f X L, K* p , K D , p d , HBT. J/ ψ ( ) D( ) m c =1.2-1.5 GeV/c 2. Q 2. v 2 saturates. b T saturates. time.

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Open charm and charmonium production at RHIC

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  1. (1) Motivations (2) Results from STAR and PHENIX (3) Conclusions and outlook Open charm and charmonium production at RHIC An Tai

  2. J/y, D W f X L, K* p, K D, p d, HBT J/ψ( ) D( ) mc=1.2-1.5 GeV/c2 Q2 v2 saturates bT saturates time Heavy flavor probing the matter properties at early stage in heavy ion collisions, gluon structure function in nucleus.

  3. Number of Participants Impact Parameter Geometry of Nucleus-Nucleus Collisions Npart – No of participant nucleons Nbinary – No of binary nucleon-nucleon collisions

  4. QGP However, J/ψ may be formed through coalescence at RHIC J/ψ enhancement J/psi dissociation in QGP ? Heavy flavor production is a crucial probe of a QGP Debye Screening < Size of J/ψ, a bound state can not exist J/ψ suppression ! New lattice QCDJ/ψ survives up to 1.6 Tc

  5. q q M. Djordjevic and M. Gyulassy QM04 c-quark energy loss testing the dead-cone effect D. Kharzeev, PLB 519 (2001) 199-206 Another stringent test of jet energy loss in a QGP

  6. StatisticalCalescene Model 0.229 0.504 0.190 0.075 0.214 Is the charm quark hadronization modified by the thermal medium ? Statistical model: A. Andronic etc. nucl-th/0209035 and private communication

  7. STAR PHENIX STAR --- TPC, TOF, EMCal -- large acceptance PHENIX--- Drift chamber, RICH, EMCal, two-arm muon detector -- small acceptance, high rate capability pp, dAu, AuAu, √s=130 GeV,200 GeV

  8. Decay channels used to construct open charm (6.2%) (9.1%) About 15 M dAu minbias events are used in the analysis we also measure D from its semi-leptonic decay to electrons, D eX

  9. Mass plots from dAu data using event-mixing technique

  10. STAR preliminary Open symbol D+/D0 Solid symbol D*/D0 Results--- D spectrum and Ratios dAu minbias at √s=200 GeV

  11. central peripheral Phenix measured open charm through D eX at √s=130 and 200 GeV in Au+Au collisions No significant charm enhancement in Au+Au over pp binary scaling is observed for pT(D)>1 GeV/c

  12. Compare measurements of open charms with background-subtracted electron data in STAR A combined fit using D0 and the electron data leads =1.44± 0.20 ± 0.44 mb The band is obtained from D decay based on the power-law fit to the measured open charm spectrum. STAR preliminary

  13. pQCD calculations of charm cross section LO NLO

  14. +332 -281 cc=709b±85(stat) (sys) Charm cross section vs NLO calculations STAR preliminary √s=130 GeV cc=420b±33(stat)±250(sys) √s=200 GeV STAR cc=1400b±200(stat)±400 (sys) PHENIX PHENIX and STAR data are consistent within uncertainties. STAR measured charm cross section is higher than the NLO predictions by factor of 3-5.

  15. γp Fragmentation of a c-quark

  16. Is the fragmentation function universal ? Bare c-quark distribution from NLO coincides with D spectrum ---- Peterson’s Function is too soft for charm hadronization in hadron-hadron collisions. π+A scattering

  17. Charm quark hadronization at RHIC

  18. PHENIX: J/Ye+e- and m+m- from pp pT and rapidity shape are consistent with COM over phenix coverage.

  19. Cross section and <pT>from pp <pT>=1.80+0.23(stat.)+0.16(syst. s = 3.99 +/- 0.61(stat) +/- 0.58(sys) +/- 0.40(abs) mb

  20. Au J/y in dAu collisions at RHIC x Predicted Gluon Shadowing in d+Au d From Eskola, Kolhinen, Vogt Nucl. Phys. A696 (2001) 729-746.

  21. R. L. Thews, M. Schroedter, J. Rafelski, Phys Rev C 63, 054905 Plasma Coalescence Model PHENIX Binary Scaling Absorption (Nuclear + QGP) + final-state coalescence Absorption (Nuclear + QGP) L. Grandchamp, R. Rapp, Nucl Phys A709, 415; Phys Lett B 523, 60 J/ψ production via coalescence ? Ncc ~ 7 in central Au+Au, may be possible. Disfavor models with enhancement over binary collision scaling.

  22. Conclusions • Open charm and J/ψ are measured at RHIC in pp, dAu and Au+Au collisions. =0.709-1.4 mb, σNNJ/ψ=3.99 +/- 0.61(stat) +/- 0.58(sys) +/- 0.40(abs) µb. • The STAR measured charm cross section for NN collisions is larger than the NLO predictions. No significant charm enhancement is observed in AuAu collisions. • The measured D pt spectrum shape coincides with the bare-quark distribution from the NLO calculation. • The measured J/ψpT and rapidity distributions are consistent with Color Octet Model.

  23. Outlook Challenge and solution of STAR open charm study in heavy ion collisions (1) Test dead-cone effect of open charm energy loss, we need to measure RAA (Rcp) with an experimental uncertainty under 20% (2) v2 measurement of open charm in AA is also difficult due to large combinatorial background (3) Test charm thermalization, need to measure DsKKπ Detector upgrade is essential!

  24. TOF upgrade will greatly enhance STAR open charm study by providing better particle identification

  25. K- p+ Decay length DCA between daughters D0 DCA daughter STAR mVertex Detector will provide precision needed for our physics goals • Two layers • 1.5 cm radius • 4 cm radius • 24 ladders • 2 cm by 20 cm each • < 0.2% X0 to limit multiple scattering • ~ 100 Million Pixels • Position resolution < 10 µm, D0 cτ = 124 µm

  26. Goals --- study matter properties created at RHIC Heavy flavor energy loss Precise D spectra Charm flow D v2 Charm thermalization Yield of D+, Ds+, Lc+ Study heavy flavor with the mVertex detector Yes Charm quark must go through a thermalized partonic medium mVertex allows the same measurement 100 times faster than TPC+SVT Future of RHIC heavy flavor program is bright !!!

  27. END

  28. After and fragmentation MRST HO Peterson’s function ε=0.06 c quark =4,3,2,1 (GeV)^2 Charm quark hadronization at RHIC Higher order pQCD is in need or charm hadronization through fragmentation+recombination (R. Rapp and E. Shuryak hep-ph/0301245 ? bare c-quark spectrum, normalized to measured dn/dy NLO pQCD predictions are provided by R. Vogt, hep-ph/0203151

  29. Mass plots from dAu data using event-mixing technique

  30. With the 10-20 more data in run4 and future detector upgrade (TOF, new vertex detectors), heavy flavor program will address the many outstanding issues related the matter properties formed at RHIC Heavy flavor energy loss Precise D spectra Charm flow Charm thermalization Yield of D+, Ds+, Lc+ J/ψ suppression or enhancement Outlook Charm quark must go through a partonic medium Yes

  31. Charm quark hadronization at RHIC The measured D pt spectrum shape coincides with the bare-quark distribution from the NLO calculation. Data favor a fragmentation function peaked at x~ 1 bare c-quark spectrum, normalized to measured dn/dy STAR preliminary

  32. After and fragmentation MRST HO Peterson’s function ε=0.06 c quark =4,3,2,1 (GeV)^2 Charm quark hadronization at RHIC The measured D pt spectrum shape coincides with the bare-quark distribution from the NLO calculation. Data favor a fragmentation function peaked at x~ 1 bare c-quark spectrum, normalized to measured dn/dy STAR preliminary

  33. R. L. Thews, M. Schroedter, J. Rafelski, Phys Rev C 63, 054905 Plasma Coalescence Model PHENIX Binary Scaling Absorption (Nuclear + QGP) + final-state coalescence Absorption (Nuclear + QGP) L. Grandchamp, R. Rapp, Nucl Phys A709, 415; Phys Lett B 523, 60 J/ψ production via coalescence ? Ncc ~ 7 in central Au+Au, may be possible. Disfavor models with enhancement over binary collision scaling.

  34. Open charm spectrum is hard ! STAR preliminary Phenix: Phys. Rev. Lett. 88, 192303(2002) D. Kharzeev,hep-ph/0310358

  35. c-quark energy loss and the dead-cone effect D. Kharzeev, PLB 519 (2001) 199-206 M. Djordjevic and M. Gyulassy QM04 Another stringent test of jet energy loss in a QGP

  36. ratios -- consistent with other experiments STAR preliminary Open symbol D+/D0 Solid symbol D*/D0 CDF: hep-ex/0307080 HERA: www-h1.de/h1/www/publications/conf_list.html e+e-: hep-ph/0312054 Statistical model: A. Andronic etc. nucl-th/0209035 and private communication.

  37. γp Charm hdronization Fragmentation of a c-quark

  38. After and fragmentation ε=0.06 Is the fragmentation universal ? momentum degradation due to fragmentation can be counter-balanced by initial Bare c-quark spectrum π+A scattering at 350 GeV/c

  39. Cronin Effect: pT broadening Parton initial state multiple scattering leads to broadening of J/y pT distribution x2~ 0.003 x2~ 0.01 Broadening comparable to lower energy (s = 39 GeV in E866) x2~ 0.1

  40. STAR D spectrum and single electron data are consistent dAu minbias at √s=200 GeV dσcc/dy=0.30±0.04(stat.)±0.09(syst.) mb STAR preliminary

  41. NLO c-quark XF distribution coincides with open charm XF distribution S. Frixione, M. Mangano and P. Nason (hep-ph/9702287) in their summary paper of heavy quark production: “ We conclude that, when using the central value of the charm mass, mc =1.5 GeV, favored by the total cross section measurements, the theoretical results for the p2T spectrum can describe the data well, only if a large kT kickis applied to the fragmented curve. Therefore, there seems to be a potential discrepancy between theory and experiments in the p2T spectrum in charm hadroproduction. From a different point of view, however, the discrepancy may be interpreted as the signal that some of the other theoretical assumptions are not totally sound. For example, the Peterson fragmentation function may not be suitable to describe the hadronization process in hadronic collisions; the data would suggest a function more peaked towards the x≃ 1 region. Moreover, higher-order perturbative corrections may also play a role.”

  42. After and fragmentation ε=0.06 Is the fragmentation universal ? momentum degradation due to fragmentation can be counter-balanced by initial Bare c-quark spectrum π+A scattering at 350 GeV/c

  43. c-quark energy loss and the dead-cone effect D. Kharzeev, PLB 519 (2001) 199-206 M. Djordjevic and M. Gyulassy QM04 Another stringent test of jet energy loss in a QGP

  44. FONLL and CDF data

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