Heavy Quark Probes of Hadronization of Bulk Matter at RHIC Huan Zhong Huang Department of Physics and Astronomy University of California at Los Angeles Department of Engineering Physics Tsinghua University Collisions at high p T (pQCD) At sufficiently large transverse momentum, let us consider the process: p + p hadron + x 1) f(x, 2 ) parton structure function 2) ab->cd pQCD calculable at large 2 3) D(z h, 2 ) Fragmentation function To produce heavy quark pairs, the CM energy must>2m Heavy Quark Production Mechanism Sensitive to initial gluon density and gluon distribution D0D0 J/ K+K+ l l K-K- e-/-e-/- e+/+e+/+ e-/-e-/- e+/+e+/+ Energy loss when propagating through dense medium Different scaling properties in central and forward region indicate shadowing, which can be due to CGC. Suppression or enhancement of charmonium in the medium is a critical signal for QGP. Sensitive to initial gluon density and gluon distribution Parton Distribution Function Important Uncertainties in gluon structure function of the proton x CTEQ5M1 CTEQ5HJ MRST2001 Band experimental constraints J. Pumplin et al, JHEP07(2002)012 Fragmentation Functions Fragmentation Functions from e+e Collisions Belle Data Charm Mesons from Hadronic Collisions Charm meson p T ~ follow the NLO charm quark p T -- add k T kick -- harder fragmentation ( func or recombination scheme) k T Kick? What about k L ? The x F distribution matches the NLO charm quark x F ! Belle Puzzle ! PRL 89, (2002) (e + e - J/ cc) (e + e - J/ X) = An order of magnitude higher than theoretical predictions -- B.L. Ioffe and D.E. Kharzeev, PRD 69, (2004) These results challenge our current understanding of how charm quarks/mesons are produced. We may question our view for the underlying charm production process, e.g., the universality of fragmentation process and the fragmentation schemes ! K ~ 1.5 Neutral D mesons LO QCD does not reproduce the cross sections ! K Factor !! K ~ 4.5 Charged D mesons K factor energy, particle dependent ! Charm-Beauty different ! We dont know the production mechanism at all ! Detecting D-Mesons via Hadronic Decays Hadronic Channels: D 0 K (B.R.: 3.8%) D 0 K (B.R.: 6.2% 100% ( ) = 6.2%) D K p(B.R.: 9.1%) D * D 0 (B.R.: 68% 3.8% (D 0 K ) = 2.6% ) c p K (B.R.: 5%) General Techniques for D Reconstruction 1.Identify charged daughter tracks through energy loss in TPC 2.Alternatively at high p T use h and assign referring mass (depends on analysis) 3.Produce invariant mass spectrum in same event 4.Obtain background spectrum via mixed event 5.Subtract background and get D spectrum 6.Often residual background to be eliminated by fit in region around the resonance Exception D*: search for peak around m(D*)-m(D 0 ) = GeV/c 2 D0D0 D0D0 D*D* Detecting Charm/Beauty via Semileptonic D/B Decays Semileptonic Channels: D 0 e + + anything (B.R.: 6.87%) D e + anything (B.R.: 17.2%) B e + anything (B.R.: 10.2%) single non-photonic electron continuum Photonic Single Electron Background: conversions ( 0 ) 0, Dalitz decays , , decays (small) Ke3 decays (small) ~7.6M AuAu 200GeV Run IV P05ia production 0~80% Min. Bias. |Vz| < 30cm Electrons can be separated from pions. But the dEdx resolution is worse than d+Au Log 10 (dEdx/dEdx Bichsel ) distribution is Gaussian. 2 Gauss can not describe the shoulder shape well. Exponential + Gaussian fit is used at lower p T region. 3 Gaussian fit is used at higher p T region. 2 /ndf = 65/46 0.3