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Heavy Quarks and Heavy Quarkonia at RHIC

Heavy Quarks and Heavy Quarkonia at RHIC. April 7 th 2006 DongJo Kim Department of Physics University of Jyvaskyla, Finland. Outline of Talk. 1-(2). A short Overview of RHIC results. RHIC history Jet-Quenching (pion R AA , Jet suppression)

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Heavy Quarks and Heavy Quarkonia at RHIC

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  1. Heavy Quarks and Heavy Quarkonia at RHIC April 7th 2006 DongJo Kim Department of Physics University of Jyvaskyla, Finland

  2. Outline of Talk 1-(2) • A short Overview of RHIC results. • RHIC history • Jet-Quenching (pion RAA, Jet suppression) • Flow ( light hadrons, even heavier particles) • Extension from Light quarks to heavy quarks • How to measure Heavy flavor ? • Semi-leptonic heavy flavor decay (Cocktail/Converter) • J/Ψ • PHENIX heavy flavour measurement • Open charm Results( RAA , charm flow ) Radiative energy loss, bottom contribution • J/psi Results ( RAA ) Suppression (Screening) vs Enhancement (recombination) • Summary 1-(2) 4-(1) 4-(1) 4-(2)

  3. RHIC History RHIC program is operating very successfully. PHENIX online data transfer and reconstruction remarkable

  4. The matter is extremely opaque Suppression is very strong (RAA=0.2!) and flat up to 20 GeV/c Energy loss of partons in dense matter • A medium effect predicted in QCD ( Energy loss by colored parton in medium composed of unscreened color charges by gluon bremsstrahlung : LPM radiation ) Gyulassy, Wang, Vitev, Baier, Wiedemann… See nucl-th/0302077 for a review. Baier, Dokshitzer, Mueller, Peigne, Shiff, NPB483, 291(1997), PLB345, 277(1995), Baier hep-ph/0209038

  5. Collective Flow Identified charged hadron v2 indicates • Early thermalization • Constituent quark scaling  Partonic collectivity Even Φ flows, within the errors consistent with other hadrons

  6. How to measure Heavy Flavor ? Phys. Rev. Lett. 88, 192303 (2002) • STAR • Direct D mesons hadronic decay channels in d+Au • D0Kπ • D±Kππ • D*±D0 π • Single electron measurements in p+p, d+Au • PHENIX • Single electron measurements in p+p, d+Au, Au+Au sNN = 130,200,62.4 GeV • Experimentally observe the decay products of Heavy Flavor particles (e.g. D-mesons) (* DongJo ) • Hadronic decay channels DKp, D0p+ p- p0 • Semi-leptonic decays De(m) K ne

  7. New Electron Results Charm/Bottomelectrons Signal/Background • S/B > 1 for pT > 1 GeV/c Run04: X=0.4%, Radiation length Run02: X=1.3% We use two different methods to determine the non-photonic electron contribution (Inclusive = photonic + non-photonic ) • Cocktail subtraction – calculation of “photonic” electron background from all known sources • Converter subtraction– extraction of “photonic” electron background by special run with additional • converter (X = 1.7%)

  8. Non-Photonic Electron Spectra Proton-Proton Baseline Gold-Gold Suppression • Fixed Order Next-to-Leading Log pQCD calculation • (M. Cacciari, P. Nason, R. Vogt • hep-ph/0502203 ) Clear high pT suppression developing towards central collisions

  9. Suppression of High pT Charm Strong modification of the spectral shape in Au+Au central collisions is observed at high pT

  10. dNg/dy=1000 Theory Comparison M. Djordjevic, M. Gyulassy, S.Wicks, Phys. Rev. Lett. 94, 112301 Disagreement with PHENIX preliminary data!

  11. dNg/dy=3500 How can we solve the problem? N. Armesto et al., Phys. Rev. D 71, 054027 (2005) Reasonable agreement, but the dNg/dy=3500 is not physical!

  12. Theory Comparison (1) q_hat = 0 GeV2/fm (4) dNg / dy = 1000 (2) q_hat = 4 GeV2/fm (3) q_hat = 14 GeV2/fm • Data favor models with large parton densities and strong coupling • Main uncertainty: • Bottom contribution at high pT Theory curves (1-3) from N. Armesto, et al., hep-ph/0501225 (4) from M. Djordjevic, M. Gyulassy, S.Wicks, Phys. Rev. Lett. 94, 112301

  13. Electrons Pions + Elastic Energy loss ? First results indicate that the elastic energy loss may be important M. G. Mustafa, Phys.Rev.C72:014905,2005 Plot shown by Wicks/Horowitz at HF workshop In BNL Dec 05 as = .3

  14. Charm Flows v2 (D) = v2 (p) v2 (D) = 0.6 v2 (p) v2 (D) = 0.3 v2 (p) Charm quark exhibit a degree of thermalization ~ comparable to that of light partons Theory curves from:Greco, Ko, Rapp: Phys. Lett. B595 (2004) 202

  15. Charming? Summary (1) q_hat = 0 GeV2/fm (4) dNg / dy = 1000 (2) q_hat = 4 GeV2/fm (3) q_hat = 14 GeV2/fm • Electrons from heavy flavor decays were measured at s = 200 GeV in Au+Au collisions at RHIC • Nuclear modification factor RAA shows a strong suppression of the electrons at high pT in Au+Au collisions • Observed RAAfavors models with large parton densities and strong coupling • Charm flows! v2(D) ~ 0.6 x v2(p) , indicating substantial coupling of the charm quarks to the bulk dynamics of the medium

  16. Charm suppression and Flow In a calculation by Teaney and Moore (hep-ph/0412346), they calculate the expected elliptic flow (v2) and transverse momentum modifications for different charm quark diffusion coefficients (free parameter). The two effects go hand in hand.

  17. Heavy Quarkonia A .Different predictions on J/Ψ behaviour when QGP is formed • Color screening will lead to suppression of charmonium production in heavy ion collisions (T. Matsui, H. Satz, Phys. Lett. B178(1986)416). • Lattice QCD results show that the confining potential between heavy quarks is screened at high temperature. This screening should suppress bound states such as J/Ψ. However, recent lattice results indicate that the J/Ψ spectral functions only show modest modification near the critical temperature, and thus may not be suppressed until higher T. • But after taken the recombination into account, • much less suppression or even enhancement is predicted • A. Andronic, P.B. Munzinger et al., nucl-th/0303036 • L. Grandchamp, R. Rapp, hep-ph/0103124 • R.L. Thews et al., Phys. Rev. c63(2001)054905 • free energy : S.Digal et al. Phys.Rev.D64(2001)094015 • linear comb. of both: C.Y.Wong hep-ph/0509088 • internal energy: W.M.Alberico et al. hep-ph/0507084 B .Disentangle Normal nuclear effects Gluon shadowing, Nuclear Absorption Initial state energy loss , Cronin effect.

  18. How does PHENIX see the J/ ? (* DongJo ) J/  e+e– identified in RICH and EMCal • || < 0.35 • p > 0.2 GeV J/μ+μ– identified in 2 fwd spectrometers • 1.2 < || < 2.4 • p > 2 GeV Centrality and vertex given by BBC in 3<||<3.9

  19. Computing the J/ yield For Au+Au or Cu+Cu collision : ~ Invariant yield : : number of ‘s reconstructed : probability for a thrown and embeded into real data to be found (considering reconstruction and trigger efficiency) : total number of events : BBC trigger efficiency for events with a : BBC trigger efficiency for minimum bias events i : i-th bin (centrality for e.g.)

  20. Signal extraction in Cu+Cu –1.95 < y < –1.70 • Cuts : • Dimuons cuts • 2.6 < mass < 3.6 GeV/c² • 1.2 < |rapidity| < 2.2 • Track quality cuts • … • Combinatoric background from uncorrelated dimuons : • Nbgd = 2√(N++. N––) • Signal = number of counts within the J/ invariant mass region • (2.6 – 3.6 GeV/c²) after subtracting Nbgd to the distribution of the opposite sign dimuons. • Systematic errors : ~10% from varying fits of the background subtracted signal. Also account for the physical background that can be included into the previous counting.

  21. Background sources • Physical background: correleted dimuons • Drell-Yan: • Open charm: D, D  µ± + … • Combinatoric background: uncorrelated dimuons • , K  µ + …(decay before the absorber)

  22. Getting acc*eff correction factors in Cu+Cu Acc*eff vs rapidity (statistical errors only) Acc*eff vs centrality (statistical errors only) Acc*eff vs pT (statistical errors only) • Using Monte Carlo J/generated by PYTHIA over 4π • embed the J/ within muon arm acceptance into real minimum bias Cu+Cu data • Apply to them the same triggers and signal extraction method as the ones applied to the data • Acc.eff(i) is the probability that a J/ thrown by PYTHIA in a given bin i to survive the whole process followed by the data • Systematic errors : • 5% from track/pair cuts and uncertainities in pT, y and z-vertex input distribution • 8% from run to run variation (mainly due to the varying number of dead channels in MuTr).

  23. RHIC : beyond cold nuclear effects ? RdA Phys. Rev. Lett 96, 012304 (2006) 1 mb σabs =1 mb σabs =3 mb 3 mb Suppression Factor ~ 2 rapidity • Available d+Au data : • Weak shadowing (modification of gluon distribution) and weak nuclear absorption (σabs ~ 1mbfavored) • Au+Au data : even compared to the « worst »σabs~ 3mb case • Factor 2 of suppression beyondcold effectsin the most central Au+Au bin Number of participants

  24. RHIC vs SPS (I) : raw comparison PHENIX : |y|~1.7 PHENIX cold effect NA50 cold effect PHENIX Cu+Cu PHENIX Au+Au NA50 Pb+Pb NA60 In+In • SPS : • √s ~ 17 GeV i.e. a factor 10 below RHIC • Cold effect = normal nuclear absorptionσabs = 4.18 ± 0.35 mb • Maximum ε ~ 3 GeV/fm3 (τ0 = 1) • Compare to RHIC : • Cold effect = shadowing + nuclear absorptionσabs ~ 1mb (Vogt, nucl-th/0507027) • Maximum ε ~ 5 GeV/fm3 (τ0 = 1), higher than at SPS, but still, the same pattern of J/ suppression ! SPS normalized to NA51 p+p value (NA60 preliminary points from Arnaldi, QM05).

  25. RHIC vs SPS (II) : extrapolating suppression models (Hadronic?) co-mover scattering Direct suppression in a hot medium : Cu+Cu Au+Au • Suppression models in agreement with NA50 data overestimatethe suppression when extrapolated at RHIC energies : • quite striking for mid and most central Au+Au bins • already the case for Cu+Cu most central bins ?

  26. Some recombination effects ? • Adding some regeneration that partially compensates the suppression : there is a better agreement between the model and the data. Grandchamp et al. hep-ph/0306077 Direct suppression in a hot medium : Cu+Cu Au+Au Regeneration : Cu+Cu Au+Au Total : Cu+Cu Au+Au

  27. Recombination predictions for < pT²> vs Ncoll p+p, d+Au, Cu+Cu, Au+Au Open markers : |y|<0.35 Solid markers : |y|~1.7 No recombination No recombination With recombination With recombination • Recombination ( Thews et al., nucl-th/0505055 ) predicts a narrower pT distribution with an increasing centrality, thus leading to a lower <pT²> • Within the large error bars : • <pT²> seems to be consistent with a flat dependence • data falls between the two hypothesis  partial recombination ?

  28. Recombination predictions vs rapidity No recombination All recombination • Recombination ( Thews et al., nucl-th/0505055 ) predicts a narrower rapidity distribution with an increasing Npart. • Going from p+p to the most central Au+Au : no significant change seen in the shape of the rapidity distribution.

  29. Summary PHENIX preliminary results on J/dileptons at forward and mid-rapidity in Cu+Cu and Au+Au : • Suppression pattern • Beyond cold nuclear effects, at least factor 2 of suppression in most central Au+Au events • Similar to SPS suppression, despite a higher energy density reached • Overestimated by models in agreement with NA50 data and extrapolated at RHIC energy • Understandable as recombinations that partially compensate the J/ suppression ? • Still open question (test vs <pT²> dependance and rapidity distribution) • Alternate explanations ? • Direct J/ is not melting at present energy densities ? Only the higher mass resonances ’ and χc ? (recent lattice QCD results) • Need to improve knowledge on cold nuclear effects at RHIC

  30. Summary • A wealth of new PHENIX data on heavy quarks and heavy quarkonia. • Charm is a very optimal probe of thermalization and properties of the medium, but the price for this may well be the loss of a probe via quarkonia for deconfinement.

  31. J/Ψ Analysis Status Analysis Status • 20004 Au+Au,2005 Cu+Cu( ppg member ) • Acceptance x Efficiency corrections • LVL2 efficiency • Fine Detector response tuning • V2 analysis • 2005 , p+p( ppg member ) & run6 status • large statistics working in progress • Finalizing all necessary stuffs • Single muon Analysis Status • QM05 Results for Light Hadrons at 200GeV • Cu+Cu 62GeV by Hot Quark 2006 at Italy, May 15th – 20th ( +Prompt muons ) • Y-PHENIX Computing Farm

  32. Thanks !!! • New Life begins in Finland • New Alice Analysis begins ! • New baby is coming ! • Lots of Sports activities !

  33. Backup slides • Charm Raa more from GLV • PHENIX/STAR comparisons • Cocktail Analysis • Electron spectra in p+p collisions (FONLL)

  34. b+ce- b 0 g Why, according to pQCD, pions have to be at least two times more suppressed than single electrons? Suppose that pions come from light quarks only and single e-from charm only. Pion and single e- suppression would really be the same. • However, • Gluon density to pions increases the pion suppression, while 2) Bottom contribution to single e- decreases the single e- suppression leading to at least factor of 2 difference between pion and single e- RAA.

  35. RAA(e-) / RAA(0)> 2

  36. Plot shown by Wicks/Horowitz What is the difference between these plots? 1. alpha_s = 0.3 (left) and alpha_s = 0.4 (right) 2. The STAR data shown at QM2005 and in their proceedings are different.

  37. Heavy quark suppression with the elastic energy loss Done by Simon Wicks. CHARM BOTTOM The elastic energy loss significantly changes the charm and bottom suppression!

  38. Possible Ds Measurement ? The three types of D mesons that contribute single electrons are: nameb.f. DeXpercentage contribution to electrons in PYTHIA D+ 17.2% 21.6% D0 7.7% 66.8% D+S 8.0% 11.6% Note that most all excited charm mesons do not decay semi-leptonically, but only contribute via sequential decay D*+ D0p+ 68.3% D+ p0 30.6% D+ g 1.1% D*0 D0 p0 61.9% D0 g 38.1% D+/D0 = 0.32 (PYTHIA) gives an average b.f. DeX of 9.7% PHENIX paper uses D+/D0 = 0.65  0.35 which gives b.f. DeX of 11.0% Theory prediction of Lin, Vogt, Wang uses b.f. DeX of 12.0%

  39. Not All Experiments Agree Either 0.4 0.2 Also, can the theory resolve an RAA suppression value of 0.2? Is the parton density then too high? RAA agrees, but the proton-proton references are different by ~ 50%.

  40. Comparison Not shown were "30-40%" systematic errors.

  41. Cocktail Subtraction Analysis Calculate inclusive single electron spectrum from all known electron sources: p0 Dalitz decay (dominant contributor at low pt) Photon conversions in PHENIX material Other light meson’s (h, h’, r, w, f) leptonic decays Direct radiation contribution Weak kaon decays electrons (Ke3) Input to the Cocktail p0 & p± invariant pT distributions as published by PHENIX Yield ratios of other light mesons to pions as measured at RHIC (where available) Use mT scaling of pion momentum distribution for light mesons Photon conversions from full simulation of PHENIX apparatus Direct g and Ke3 from PHENIX measurements • Excess of the data over the Cocktail prediction can be interpreted as heavy flavor particle semi-leptonic decays contribution

  42. Non-Photonic Single Electron Spectra pp @ s = 200 GeV Note: Bottom dominates for pT> 2.5 GeV/c PHENIX data • Comparison with PYTHIA (tuned to available data) • pT < 1.5 GeV/c: reasonable • pT > 1.5 GeV/c: spectra “harder” than PYTHIA LO • hard fragmentation? • bottom enhancement? • higher order contributions? • Comparison with FONLL • Fixed Order Next-to-Leading Log pQCD calculation (M. Cacciari, P. Nason, R. Vogt hep-ph/0502203 ) • better description of spectral shape • still room for further contributions • from jet fragmentation?

  43. Why Heavy Quarks ? c B. Muller b S. Bethke • Heavy quarks (charm and beauty) - produced early in the collision. Live long enough to sample the plasma • Intrinsic large mass scale allows precise calculations What can we look in order to find out the characteristics or properties of the medium(QGP) • Yields of charm and beauty pairs compared to first principle lattice simulations determine the energy density and temperature  J/Ψ suppression • Comparison between light and heavy quark suppression distinguishes between theoretical models of energy loss in the QGP  Charm vs Light quark energy loss ( Jet-Quenching ) • Mass dependence of diffusion of heavy quarks determines plasma properties, e.g. viscosity and conductivity Charm flow

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