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J/ y Measurement in Heavy Ion Collisions at RHIC

1. Workshop on “Frontiers in the physics of quark-gluon-plasma” 7/8/2006, RIKEN. J/ y Measurement in Heavy Ion Collisions at RHIC. Taku Gunji, CNS, University of Tokyo For the PHENIX Collaboration. 2. Outline. Physics Motivation Charmonium in the Medium Cold Matter Effects

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J/ y Measurement in Heavy Ion Collisions at RHIC

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  1. 1 Workshop on “Frontiers in the physics of quark-gluon-plasma” 7/8/2006, RIKEN J/y Measurement in Heavy Ion Collisions at RHIC Taku Gunji, CNS, University of Tokyo For the PHENIX Collaboration

  2. 2 Outline • Physics Motivation • Charmonium in the Medium • Cold Matter Effects • Results from d+Au Collisions • QGP Effects • Color Screening and cc-bar coalescence • Results from A+A Collisions • Comparison to theoretical models • Summary and Outlook

  3. 3 Physics Motivation • Heavy Quarks carry the information of the early stage of collisions. • Charm quarks are massive even at RHIC • Creation takes place only at the begging of collisions via the hard process. • Sensitive to gluon PDF in nuclei. • Well calibrated by p+p collisions • Yields scale with Nbinary (without medium effect) • No Chemical equilibrium. Abundance will be frozen. • Charmonium = “Probe of De-confinement” • Color Screening Effect by QGP

  4. 4 • cc coalescence • Dissociation by • secondary mesons Charmonium in the Medium • J/y production and evolution of the medium • All stage of collisions modify the J/y yield. Initial stage Hot and dense medium Nuclear medium Mixed Phase Freeze out • Gluon • Shadowing • CGC • Nuclear • Absorption • Cronin effect • Color screening • Dissociation by • gluons Cold Matter Effect QGP Effect

  5. 5 • cc coalescence • Dissociation by • secondary mesons Charmonium in the Medium • J/y production and evolution of the medium • All stage of collisions modify the J/y yield. Initial stage Hot and dense medium Nuclear medium Mixed Phase Freeze out • Gluon • Shadowing • CGC • Nuclear • Absorption • Cronin effect • Color screening • Dissociation by • gluons Cold Matter Effect QGP Effect

  6. 6 Eskola et al. NPA696 (2001) 729 Anti Shadowing Shadowing gluons in Pb / gluons in p x Cold Matter Effects • Initial state effect: • Gluon Shadowing (or CGC gluon saturation) • Depletion of Gluon PDF in nuclei at small x. • Final state effects: • Nuclear Absorption • Break up interaction of J/y or pre-resonance c-cbar state by spectators • Cronin effect • Initial state multiple scattering of partons • d+Au collisions give the hints of these effects Converage of X in Au By PHENIX in d+Au experiments

  7. 7 Low x2 ~ 0.003 (shadowing region) 0 mb RdAu 3 mb (in gold) = Xd - XAu Results from d+Au Collisions sdAu= spp(2x197)a RdAu vs. Rapidity • Small effect from gluon shadowing • a>0.92, scale with XF not XAu • Small effect from nuclear absorption • sabs = 0-3 mb, sabs = 4.2mb at SPS Need more data to quantify these effects.

  8. 8 Color Glass Condensate • At RHIC, coherent charm production in nuclear color field at y>0 (Qs > mc) anddominant at y>2.  Description by Color-Glass-Condensate sdAu= spp(2x197)a SPS FNAL RHIC

  9. 9 • cc coalescence • Dissociation by • secondary mesons Charmonium in the Medium • J/y production and evolution of the medium • All stage of collisions modify the J/y yield. Initial stage Hot and dense medium Nuclear medium Mixed Phase Freeze out • Gluon • Shadowing • CGC • Nuclear • Absorption • Cronin effect • Color screening • Dissociation by • gluons Cold Matter Effect QGP Effect

  10. 10 J/y is “QGP thermometer” • Color Screening by the QGP • Suppression due to the Debye Screening. • Tdiss (cc) ~ Tdiss (y’) < Tdiss (J/y) • 40% J/y come from y’ and cc. • J/y ~ 0.6 J/y + 0.3cc + 0.1y’ • HERA-B exp. Phys. Lett. B 561(2003) • These effects result in the sequential melting of J/y. • J/y suppression pattern may be able to serve as a “QGP thermometer”.

  11. 11 Dissociation Temperature Datta & al, hep-lat/0409147 Alberico & al, hep-ph/0507084 Wong, hep-ph/0408020 Satz, hep-ph/0512217 M. Asakawa et al, PRL 92(2004) • Recent Lattice Results and Potential Analysis. • Question from experimentalists. • How large the “systematic error”? • J/y would survive at RHIC!? • Same as SPS? • J/y suppression at SPS can be described by feed down effect. • melting only cc and y’.

  12. 12 statistical hadronization model Ncc = 28 hep-ph/0311048 (CERN yellow rpt) Ncc = 19 Ncc = 12 Coalescence of cc-bar pairs • New Scenario of J/y production in HIC at RHIC! (negligible at SPS) • First(?) discussion by T. Matsui • Proceedings of the Second Workshop on Experiments and Detectors for a Relativistic Heavy Ion Collider (RHIC) at LBL, 1987. • Recombination of J/y from uncorrelated cc-bar pairs. • statistical coalescence • kinetic formation • two component model

  13. 13 Let’s look at the data from Au+Au andCu+Cu collisions.

  14. 14 1.2<|y|<2.4 |y|<0.35 RAA as a function of Npart • Factor of 3 suppression at most central (Au+Au/Cu+Cu) • Beyond the cold matter effects extrapolated from d+Au results. • Same suppression pattern at forward rapidity, but different pattern at mid-rapidity between Au+Au and Cu+Cu. • Pattern in Au+Au is different between mid-rapidity and forward-rapidity.

  15. 15 Au+Au Cu+Cu RAA as a function of pT • Results from forward-rapidity. • Yield of low pT J/y is suppressed in both Au+Au and Cu+Cu. • Tendency is same as SPS.

  16. 16 Used NA50 Suppression • Models describing NA50 suppression. • extrapolation of T, gluon density from SPS. SPS  RHIC : ~10x collision energy ~2-3x gluon energy density J/y suppression at RHIC is over-predicted by the suppression models that described SPS data successfully. Eur. Phys. J C42 (2005) PRL 92 (2004) 212301 PRC 68 (2003) 041902 Co-mover (sabs = 1mb) Direct dissociation +Comover

  17. 17 Coalescence Models • Models with recombination • Dissociation + Recombination Models with recombination – single charm quarks combining in the hadronization stages to form J/’s – match the observed RHIC suppression much better! Need to look at other observables. (<pT2>, y-shape) Statistic coalescence (PLB 571 (2003) 36) Statistic coalescence(PRC 68 (2003) 041902) HSD model (PRC 69 (2004) 054903) Two component model (PRL 92 (2004) 212301)

  18. 18 p+p d+AuAu+Au <pT2> = 2.51 + 0.32 L Open symbol: y ~ 0 Full & curves: y ~ 2 <pT2> • At forward rapidity (closed symbols) • <pT2> = 2.51 + 0.32 L from pp & dA • Data points are consistent with Cronin effect. • in between of direct and recombination • At mid rapidity (open symbols) • behavior in <pT2> is different from forward-rapidity. • <pT2> does not increase with L in d-Au and Au-Au. Thews (Kinetic Model) Eur.Phys.J C43, 97 (2005)

  19. 19 Rapidity Shape • No significant difference in rapidity shape, while recombination predicts narrower rapidity shape. • charm y-shape and longitudinal flow need to be evaluated. Thews (Kinetic Model) Eur.Phys.J C43, 97 (2005)

  20. 20 Only cold matter effect Au+Auy~1.7|y| ~ 0 Cold matter effect (1mb) QGP suppression Hydro + J/y transport • QGP hydro (2+1D) • Boltzman-type transport • Dissociation by gluons in QGP • No thermalization of charm • No recombination • No interaction in HG The result fits reasonably well the PHENIX data at y=1.7, but not at y=0.

  21. 21 Sequential Melting • Survival probability vs. energy density(t0 ~ 1 fm/c) • Assuming Successive Melting. • Tdiss(cc,y’) ~ Tc (dissolved) • Tdiss(J/y) ~ 2Tc (un-dissolved) • S(J/y) = 0.6 + 0.4*S(y’) • S(y’) from SPS data • Interesting idea inferred from Lattice QCD calculations. • No dynamical dissociation process. • Need to be integrated with other process. • 40% feed down is OK at RHIC? Karsch, Kharzeev & Satz: PLB637(2006)75

  22. 22 Summary • PHENIX Measured J/y in p+p, d+Au, Au+Au and Cu+Cu Collisions. • Cold matter effects are weak at RHIC energy. • Need more d+Au data to quantify these effects. • Observed the suppression in A+A collisions. • Suppression is beyond the Cold Matter Effects. • Different behavior in RAA between Au+Au and Cu+Cu at mid-rapidity. • Different behavior in RAA and <pT2> between Mid-Rapidity and Forward-Rapidity. • Weak suppression compared to “full” suppression • Many works on the theoretical predictions. • Suppression (dissociation by gluons) + recombination • Static color screening + feed down • QGP hydro + transport of J/y • All describe better compared to “full” suppression models.

  23. 23 Outlook • We need to improve the current situation both experimentally and theoretically. • Experiment : • More data : d+Au, A+A and p+p (reference) • J/y v2 measurements : RP detector in PHENIX from 2007 • feed down effects : cc analysis in p+p is underway. • Theoretical : • Calculations with complete processes are needed. • Cold Matter Effects • modified PDF, Cronin effect, Nuclear Absorption • Dissociation due to Debye screening (sequential melting; feed-down effect) and dynamical effects in QGP and HG • Medium Properties and effects on dissociation cross section, binding energy, charm mass … • Recombination process • Charm cross section, rapidity, pT, charm flow, jet quenching

  24. 24 BW fit of D-meson spectra From STAR. Freeze out and collective Behavior of charm. AuAu Central charm hadron AuAu Central , K, p Charm Production at RHIC Yield vs. pT for two rapidity ranges in p+p collisions. Charm vs. y Need to understand charm production and its modification in the medium. Non-photonic e spectra from PHENIX. Implication of charm Energy loss Non-photonic e v2 from PHENIX. Thermalization of Charm.

  25. Back Up Slides

  26. 11 PHENIX Experiment • J/y measurement at wide y coverage. Central Arms: Hadrons, photons, electrons J/y  e+e- |h|<0.35 Pe > 0.2 GeV/c Df = p (2 arms x p/2) • Muon Arms: • Muons at forward rapidity • J/y  m+m- • 1.2< |h| < 2.4 • Pm > 2 GeV/c • Df = 2p

  27. (in gold) = Xd - XAu XAu, XF dependence of a sdAu= spp(2x197)a • Shadowing is weak. • Not scaling with X2 but scaling with XF. • Coincidence? • Shadowing • Gluon energy loss • Nuclear Absorption • Sudakov Suppression? • Energy conservation • hep-ph/0501260 • Gluon Saturation? • hep-ph/0510358 E866, PRL 84, (2000) 3256NA3, ZP C20, (1983) 101 PHENIX, PRL96 (2006) 012304

  28. Cronin Effect • a vs. pT for 3 xAu region • Comparison to lower energy results. • E866 at s = 39 GeV. • Trend of pT broadening at RHIC is consistent With lower energy results High x2 ~ 0.09 Low x2 ~ 0.003

  29. J/y measurements at SPS • Suppression in S+A • turned out to be similar to p+A • Anomalous suppression in Pb+Pb J/y Suppression as a function of pT (Pb+Pb)

  30. Comover Interaction • In HG, survived J/y’s interact with secondary hadrons: J/y + h  DD. • Crucial parameter : J/y-hadron inelastic cross-section, (syhinel) a very uncertain parameter ! Theoretical estimates : syhinel ~0.1-1 mb • Dual Parton Model • Ncom = C1*Npart+C2*Ncol • syhinel ~0.46 mb A.Capella,D.Sousa, nucl-th/0303055

  31. Zhu et al. PLB 607, 107 (2005) coalescence of thermalized charm X 0.1 (Rapp) geometry only Azimuthal anisotropy of J/y • Key to differentiate recombination and transport model. • Recombination : • 10% v2 @ 2GeV/c • If charm quark v2 is same as light quark v2. • Transport model: • 0.5% v2 @ 2GeV/c • More suppression of low pT J/y in the out-of-plane. (“Geometry only”) • Need more statistics and good RP resolution. • RP detector at Run7

  32. PHENIX Preliminary J/y Polarization • Sensitive to Production Mechanism J/y production models predict different polarization. CEM and CSM: no polarization COM: transverse at high PT Ioffe and Kharzeev, hep-ph/0306176: transverse (~0.35-0.40) at low PT if QGP is formed Khoze, Martin, Ryskin, and Stirling, hep-ph/0410020: longitudinal polarization at high PT Run3 d+Au Results consistent with no polarization, large error bars due to low statistics.

  33. QM05 J/y in Ultra-Pheriperal Collisions • Photo-production gpJ/yp : • Sensitive to Gluon distribution at small x. J. Nystrand, NPA 752 (2005) 470c dsJ/y/dy|y=0 = 44 ± 16 (stat) ± 18 (syst) mb

  34. First U measurements • Preliminary results from run5 p+p muon arms

  35. FG Mixed event BG cc1 cc2 Meeg-Mee [GeV] Meeg-Mee [GeV] First cc observation • From run5 p+p central arms • Further analysis is on going.

  36. 10 Color Screening by the QGP • Probe of the “de-confinement” • T. Matsui and H. Satz (1986) • Suppression due to the Debye Screening in the de-confined phase • Screening Radius rD(T) decreases with temperature T. • whenrD(T) falls below the binding radius ri of QQ-bar statei , state i cannot exist. • Tdiss (cc) ~ Tdiss (y’) < Tdiss (J/y)

  37. 14 Various Coalescence Models • Statistical Hadronization (A. Andronic et al.) • All Charmonium dissolved in the QGP • Charm equilibrium in the QGP • Open and Closed charm form at the freeze-out. • Kinetic Formation (Thews et al.) • Continuous formation/dissociation of J/y in the QGP • Used vacuum binding energy of J/y • 2 Component Model (R. Rapp et al.) • In-medium binding energies of J/y inferred from Lattice. • formation/dissociation of J/y in the QGP and HG • statistical coalescence at the freeze-out • rate equation in the thermal fireball model.

  38. 20 Thews (Kinetic Model) Eur.Phys.J C43, 97 (2005) Rapp et al. (2-Component) PRL 92, 212301 (2004) Coalescence Models • Models with recombination Models with recombination – single charm quarks combining in the hadronization stages to form J/’s – match the observed RHIC suppression much better! Need to look at other observables. (<pT2>, y-shape)

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