An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 1 Open charm and charmonium production at RHIC (1) Motivations (2) Results from STAR and PHENIX (3) Conclusions and outlook An Tai

Aug.9-14, 2004, CCAST Workshop, Beijing 2 J/  D     K*  K  p  d, HBT v 2 saturates  T saturates Q2Q2 time Heavy flavor probing the matter properties at early stage in heavy ion collisions, gluon structure function in nucleus. J/ψ( ) D( ) m c = GeV/c 2

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 3 Geometry of Nucleus-Nucleus Collisions N part – No of participant nucleons N binary – No of binary nucleon-nucleon collisions

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 4 Heavy flavor production is a crucial probe of a QGP J/psi dissociation in QGP ? QGP Debye Screening < Size of J/ψ, a bound state can not exist  J/ψ suppression However, J/ψ may be formed through coalescence at RHIC  J/ψ enhancement ! New lattice QCD  J/ψ survives up to 1.6 T c

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 5 c-quark energy loss testing the dead-cone effect M. Djordjevic and M. Gyulassy QM04 D. Kharzeev, PLB 519 (2001) q q Another stringent test of jet energy loss in a QGP

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 6 Is the charm quark hadronization modified by the thermal medium ? Statistical Calescene Model Statistical model: A. Andronic etc. nucl-th/ and private communication

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 7 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 PHENIX STAR

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 8 (9.1%) we also measure D from its semi-leptonic decay to electrons, D  e  X Decay channels used to construct open charm (6.2%) About 15 M dAu minbias events are used in the analysis

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 9 Mass plots from dAu data using event- mixing technique

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 10 Results--- D spectrum and Ratios Open symbol D+/D0 Solid symbol D*/D0 dAu minbias at √s=200 GeV

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 11 Phenix measured open charm through D  e  X at √s=130 and 200 GeV in Au+Au collisions central peripheral No significant charm enhancement in Au+Au over pp binary scaling is observed for p T (D)>1 GeV/c

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 12 A combined fit using D 0 and the electron data leads =1.44± 0.20 ± 0.44 mb Compare measurements of open charms with background-subtracted electron data in STAR The band is obtained from D decay based on the power-law fit to the measured open charm spectrum.

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 13 pQCD calculations of charm cross section LO NLO

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 14 Charm cross section vs NLO calculations PHENIX and STAR data are consistent within uncertainties. STAR measured charm cross section is higher than the NLO predictions by factor of 3-5.  cc =709  b±85(stat) (sys) √s=130 GeV  cc =420  b±33(stat)±250(sys) √s=200 GeV STAR  cc =1400  b±200(stat)±400 (sys) PHENIX

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 15 Fragmentation of a c-quark γpγp

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 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

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 17 Charm quark hadronization at RHIC

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 18 PHENIX: J/   e+e- and  +  - from pp p T and rapidity shape are consistent with COM over phenix coverage.

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 19 Cross section and from pp  = /- 0.61(stat) +/- 0.58(sys) +/- 0.40(abs)  b = (stat.)+0.16(syst.

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 20 Predicted Gluon Shadowing in d+Au J/  in dAu collisions at RHIC From Eskola, Kolhinen, Vogt Nucl. Phys. A696 (2001) d Au x

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 21 J/ψ production via coalescence ? R. L. Thews, M. Schroedter, J. Rafelski, Phys Rev C 63, Plasma Coalescence Model Binary Scaling Absorption (Nuclear + QGP) + final-state coalescence Absorption (Nuclear + QGP) L. Grandchamp, R. Rapp, Nucl Phys A709, 415; Phys Lett B 523, 60 PHENIX Disfavor models with enhancement over binary collision scaling. N cc ~ 7 in central Au+Au, may be possible.

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 22 Conclusions Open charm and J/ψ are measured at RHIC in pp, dAu and Au+Au collisions. = mb, σ NN J/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/ψ p T and rapidity distributions are consistent with Color Octet Model.

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 23 (1) Test dead-cone effect of open charm energy loss, we need to measure R AA (R cp ) 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 ! Challenge and solution of STAR open charm study in heavy ion collisions Outlook

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 24 TOF upgrade will greatly enhance STAR open charm study by providing better particle identification

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 25 STAR  Vertex 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% X 0 to limit multiple scattering  ~ 100 Million Pixels  Position resolution < 10 µm, D 0 cτ = 124 µm DCA daughter D0D0 Decay length K-K- ++ DCA between daughters

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 26 Study heavy flavor with the  Vertex detector Goals --- study matter properties created at RHIC  Heavy flavor energy loss Precise D spectra  Charm flow D v 2  Charm thermalization Yield of D +, D s +,  c + mVertex allows the same measurement 100 times faster than TPC+SVT Charm quark must go through a thermalized partonic medium Yes

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 27 END

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 28

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 29 Charm quark hadronization at RHIC NLO pQCD predictions are provided by R. Vogt, hep-ph/ bare c-quark spectrum, normalized to measured dn/dy MRST HO Peterson’s function ε=0.06 c quark =4,3,2,1 (GeV)^2 After and fragmentation Higher order pQCD is in need or charm hadronization through fragmentation+recombination (R. Rapp and E. Shuryak hep-ph/ ?

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 30 Mass plots from dAu data using event- mixing technique

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 31 With the 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 +, D s +,  c +  J/ψ suppression or enhancement Yes Outlook Charm quark must go through a partonic medium

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 32 Charm quark hadronization at RHIC bare c-quark spectrum, normalized to measured dn/dy 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

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 33 Charm quark hadronization at RHIC bare c-quark spectrum, normalized to measured dn/dy MRST HO Peterson’s function ε=0.06 c quark =4,3,2,1 (GeV)^2 After and fragmentation 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

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 34 J/ψ production via coalescence ? R. L. Thews, M. Schroedter, J. Rafelski, Phys Rev C 63, Plasma Coalescence Model Binary Scaling Absorption (Nuclear + QGP) + final-state coalescence Absorption (Nuclear + QGP) L. Grandchamp, R. Rapp, Nucl Phys A709, 415; Phys Lett B 523, 60 PHENIX Disfavor models with enhancement over binary collision scaling. N cc ~ 7 in central Au+Au, may be possible.

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 35 Open charm spectrum is hard ! Phenix: Phys. Rev. Lett. 88, (2002) D. Kharzeev,hep-ph/

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 36 c-quark energy loss and the dead-cone effect M. Djordjevic and M. Gyulassy QM04 D. Kharzeev, PLB 519 (2001) Another stringent test of jet energy loss in a QGP

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 37 ratios -- consistent with other experiments Open symbol D+/D0 Solid symbol D*/D0 CDF: hep-ex/ HERA: www-h1.de/h1/www/publications/conf_list.html e+e-: hep-ph/ Statistical model: A. Andronic etc. nucl-th/ and private communication.

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 38 Fragmentation of a c-quark γpγp Charm hdronization

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 39 Is the fragmentation universal ? Bare c-quark spectrum After and fragmentation ε=0.06 π+A scattering at 350 GeV/c momentum degradation due to fragmentation can be counter-balanced by initial

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 40 x 2 ~ 0.1 x 2 ~ x 2 ~ 0.01 Parton initial state multiple scattering leads to broadening of J/  p T distribution Broadening comparable to lower energy (  s = 39 GeV in E866) Cronin Effect: p T broadening

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 41 STAR D spectrum and single electron data are consistent dAu minbias at √s=200 GeVdσ cc /dy=0.30±0.04(stat.)±0.09(syst.) mb

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 42 S. Frixione, M. Mangano and P. Nason (hep-ph/ ) in their summary paper of heavy quark production: “ We conclude that, when using the central value of the charm mass, m c =1.5 GeV, favored by the total cross section measurements, the theoretical results for the p 2 T spectrum can describe the data well, only if a large k T kick is applied to the fragmented curve. Therefore, there seems to be a potential discrepancy between theory and experiments in the p 2 T 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.” NLO c-quark X F distribution coincides with open charm X F distribution

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 43 Is the fragmentation universal ? Bare c-quark spectrum After and fragmentation ε=0.06 π+A scattering at 350 GeV/c momentum degradation due to fragmentation can be counter-balanced by initial

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 44 c-quark energy loss and the dead-cone effect M. Djordjevic and M. Gyulassy QM04 D. Kharzeev, PLB 519 (2001) Another stringent test of jet energy loss in a QGP

An Tai Aug.9-14, 2004, CCAST Workshop, Beijing 45 FONLL and CDF data