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J/ y production in Au+Au and Cu+Cu Collisions at RHIC

1. J/ y production in Au+Au and Cu+Cu Collisions at RHIC. Taku Gunji CNS, University of Tokyo . Heavy Ion Café 2007/2/10 . 2. Outline. Physics Motivation J/ y in the medium J/ y measurement at SPS J/ y measurement at RHIC d+Au collisions and cold matter effects

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J/ y production in Au+Au and Cu+Cu Collisions at RHIC

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  1. 1 J/y production in Au+Au and Cu+Cu Collisions at RHIC Taku Gunji CNS, University of Tokyo Heavy Ion Café 2007/2/10

  2. 2 Outline • Physics Motivation • J/y in the medium • J/y measurement at SPS • J/y measurement at RHIC • d+Au collisions and cold matter effects • Au+Au and Cu+Cu collisions • Comparison to the theoretical models • Summary & Outlook

  3. 3 Physics Motivation • J/y suppression in QGP due to the Debye Color Screening T.Matsui & H. Satz PLB178 416 (1986) • Signature of de-confinement • Debye Color Screening • Debye Radius < Rcc No formation of c-cbar bound states • Suppression depends on temperature (density) • Recent quenched lattice QCD calculations • Melting temp. for J/y ~1.5-2.5Tc • Melting temp. for cc,y’ ~1.1Tc T. Hatsuda, M. Asakawa, PRL. 92 (2004) 012001 S. Datta, et al., PRD69 (2004) 094507

  4. 4 J/y = Thermometer of QGP • 2 Key points • Feed down contribution from y’ and cc • All J/y = ~0.6 J/y (direct) + ~0.3cc + ~ 0.1y’ • Fraction is not well-understood experimentally • TJ/y ~ 2Tc and Tc, Ty’ ~ 1.1Tc Expected J/y (All) Suppression Pattern “Sequential Melting” Temperature can be deduced from magnitude of suppression. 温度

  5. 5 • cc coalescence • Dissociation by • comovers J/y 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 • thermal gluons) Cold Matter Effect Final state Effect

  6. 6 J/y measurement at SPS • NA38(S+U@19.4 GeV)、NA50(p+A@19.4 GeV, Pb+Pb@17.3GeV) Nuclear Absorption of J/y L: effective path length of J/y in nuclear target Anomalous suppression relative to nuclear Absorption • Very promising to study J/y production in A+A collisions at higher collision energy. • 10x √sNN at RHIC • 2-3x gluon density at RHIC Pb+Pb PB

  7. 7 PHENIX Experiment • PHENIX can measure J/y in wide rapidity range 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

  8. 8 RHIC cold nuclear matter effects (CNM)

  9. Xd XAu J/ in South y < 0 rapidity y Anti Shadowing Shadowing Xd XAu J/ in North y > 0 X 9 J/y in d+Au collisions • Understand the cold matter effects • Gluon Shadowing • Nuclear absorption • Cronin effect (pT broadening) • Coverage of XAu in d+Au at PHENIX gluons in Pb / gluons in p South muon arm (y < -1.2) : • large XAu  0.090 Central arm (y  0) : • intermediate XAu  0.020 North muon arm (y > 1.2) : • small XAu  0.003 Eskola, et al., Nucl. Phys. A696 (2001) 729-746.

  10. 10 Low x2 ~ 0.003 (shadowing region) 0 mb RdAu 3 mb Results of RdAu vs. y • d+Au experiments at RHIC RdAu vs. Rapidity • Tendency is consistent with the shadowing effects. • Nuclear absorption cross section : 0~3 mb. • need more data to quantify CNM effects.

  11. 11 J/y production in Au+Au and Cu+Cu collisions at RHIC

  12. 12 RAA 1 Au+Au PHENIX Final Cu+Cu PHENIX Preliminary 0 RAA vs. Npart • Final results for Au+Au : nucl-ex/0611020(submitted to PRL) • Analysis for Cu+Cu will be finalized soon!

  13. 13 Observation 1Different suppression pattern between mid-rapidity and forward-rapidity

  14. 14 RAA vs. Npart in Au+Au 1 • RAA vs. Npart. • |y|<0.35 • 1.2<|y|<2.2 RAA • Different behavior in RAA • between mid-rapidity and • forward-rapidity. • J/y suppression is larger • at forward-rapidity than • at mid-rapidity • S ~ 0.6 for Npart>100 Bar: uncorrelated error Bracket : correlated error 0 1 S = RAA (1.2<|y|<2.2)/RAA (|y|<0.35) 0

  15. 15 RAA and CNM effects RAA • CNM effects • Gluon shadowing + nuclear absorption • J/y measurement in d+Au collisions. 1 RHIC CNM effects (sabs = 0, 1, 2mb at y=0, y=2) R. Vogt et al., nucl-th/0507027 0 • Significant suppression relative to CNM effects. • CNM effects predict larger suppression at mid-rapidity, while data shows larger suppression at forward-rapidity.

  16. 16 Open charm yield in Au+Au @ 200 GeV =0 =2 Larger suppression by CGC? • Heavy quark production is expected to be suppressed due to “Color Glass Condensate” at forward-rapidity. K. L. Tuchin hep-ph/0402298 • Larger suppression of J/y at forward-rapidity (Npart>100) could be ascribed to Color Glass Condensate?

  17. 17 Larger suppression by larger feed down? • Pythia calculation (done by S. X. Oda) Red : 88 gg  c1cg  J/y Green : 89 gg  c2cg  J/y Blue : 105 gg  c2c  J/y Magenta : MSEL 5 bbbar  J/y Larger suppression of J/y yield at forward rapidity might be partly (~15%) due to the broad distribution of J/psi from chi_c.

  18. 18 Observation 2J/y suppression from final state effect is stronger at RHICcompared to SPS

  19. 19 Comparison of RAA to NA50 NA50 at SPS (0<y<1) PHENIX at RHIC (|y|<0.35) PHENIX at RHIC (1.2<|y|<2.2) • RAA vs. Npart • NA50 at SPS • 0<y<1 • PHENIX at RHIC • |y|<0.35 • 1.2<|y|<2.2 • J/y Suppression (CNM • effects included) is similar • at RHIC (y=0) compared • to at SPS (0<y<1). Bar: uncorrelated error Bracket : correlated error Global error = 12% and Global error = 7% are not shown

  20. 20 RAA and CNM NA50 at SPS (0<y<1) PHENIX at RHIC (|y|<0.35) PHENIX at RHIC (1.2<|y|<2.2) • RAA at RHIC and SPS RHIC CNM effects (sabs = 0, 1, 2mb at y=0, y=2) R. Vogt et al., nucl-th/0507027 SPS CNM effects (sabs = 4.18 mb) NA50, Eur. Phys. J. C39 (2005):355 Bar: uncorrelated error Bracket : correlated error Global error = 12% and Global error = 7% are not shown

  21. 21 RAA/CNM vs. Npart NA50 at SPS (0<y<1) PHENIX at RHIC (|y|<0.35) PHENIX at RHIC (1.2<|y|<2.2) • RAA/CNM at RHIC and SPS. CNM: • sabs = 4.18 mb for SPS • sabs = 1 mb for RHIC • Additional sys. error due to the uncertainty of CNM (0-2mb) is shown as box. Here, SPS data will have sys. errors. • J/y suppression relative • to CNM effects is larger at • RHIC for the similar Npart. • (much larger • at forward rapidity) Bar: uncorrelated error Bracket : correlated error Global errors (12% and 7%) are not shown here. Box : uncertainty from CNM effect

  22. 22 RAA vs. pT • Suppression trend is similar for forward and mid rapidity. • Suppression consistent with flat.

  23. 23 Exercise :Comparison to theoretical models

  24. 24 Dissociation by thermal gluons • Dissociation by thermal gluons • Successfully describe J/y suppression at SPS. • Gluon density extrapolated to RHIC energy R. Rapp et al., nucl-th/0608033 Nu Xu et al., nucl-th/0608010 Calculation for only y=0 • At mid-rapidity, • suppression is • weaker compared • to the dissociation • scenario in QGP.

  25. J/y c c-bar c 25 Recombination of J/y • Coalescence of c-cbar • Abundant ccbar pairs at RHIC [10-30@central Au+Au] • Dissociation + Recombination of J/y R.Rapp et al, EPJC43 (2005) 91 N. Xu at al, nucl-th/0608010 Kinetic formation model Transport model total total recombination dissociation dissociation recombination Magnitude of suppression matches better. However, tendency can not be reproduced well.

  26. 26 <pT2> vs. centrality • Another test for recombination No recombination Recombination (pQCD charm ) Recombination (thermal charm)

  27. 27 Kinetic formation model. Dissociation + recombination model (R. Rapp and so on) • Charm cross section (binary scaling) • NLO pQCD calc, PHENIX, STAR gc ~ 10 at RHIC, ~30 at LHC ¼ sc+g X.N.Wang PLB540 (2002) 62 Gluon thermal dist. (T=0.35 GeV) sJ/y+g k[GeV]

  28. 28 Transport model Dissociation + recombination model (Nu Xu et al.) ccbar  J/y +g J/y +g ccbar R. L. Thews Eur. Phys. J C43, 97 (2005)

  29. 29 Sequential Melting • RAA/CNM vs. Bjorken energy density • t0 = 1 fm/c. Be careful! • Not clear t0 at SPS • Crossing time ~ 1.6 fm/c Here, SPS data will have sys. errors . • J/y suppression at SPS • can be understood • from the melting of y’ • and cc. F. Karsch et al., PLB, 637 (2006) 75

  30. 30 Sequential Melting • RAA/CNM vs. Bjorken energy density • t0 = 1 fm/c. Be careful! • Not clear t0 at SPS and RHIC. • t0 < 1 fm/c at RHIC • Nucl. Phys. A757, 2005 Here, SPS data will have sys. errors. Bar: uncorrelated error Bracket : correlated error Global error = 12% is not shown here. Box : uncertainty from CNM effects F. Karsch et al., PLB, 637 (2006) 75 dET/dy : PHENIX, PRC 71, 034908 (2005)

  31. 31 Sequential Melting • RAA/CNM vs. Bjorken energy density • t0 = 1 fm/c Be careful! • t0 < 1 fm/c at RHIC Here, SPS data will have sys. errors. • Direct J/y melting at RHIC? • Error is large and need better • CNM measurements at RHIC. • Need to measure feed-down contribution at RHIC energy. Bar: uncorrelated error Bracket : correlated error Global error = 12% and 7% are not shown here. Box : uncertainty from CNM effects

  32. 32 Threshold Model • All J/y is suppressed above a threshold density. • Fate of J/y depends on the • local energy density • ( participants density, n) • Similar model to the sequential melting and associated to “onset of J/y suppression”. • nc = 4.0 fm-2 matches to our mid-rapidity data. (cf. n~4.32 fm-2 in most central Au+Au collisions) • K. Chaudhuri, nucl-th/0610031 • Calculation for only y=0. • Describes well mid-rapidity data. • How about forward-rapidity? nc = threshold participant density

  33. 33 Summary • First high statistic data of J/y in Au+Au and Cu+Cu collisions at mid-rapidity and forward-rapidity are available. • Suppression is larger at forward-rapidity than at mid-rapidity for Npart>100. • Suggesting initial state effect such as Color Glass Condensate? • More feed down contribution at forward-rapidity? • RAA/CNMseems to be lower at RHIC compared to at SPS • However, suppression at mid-rapidity isn’t so strong as expected by the models (destruction by thermal gluons) extrapolated from SPS to RHIC. • Suppression + Recombination models match better. • Not consistent with the picture of only y’ and cc melting at RHIC. Suppression of directly produced J/y?

  34. Backup slides

  35. Regeneration should cause narrowing of pT – does it? • Mean pT2 pretty flat • as expected in regeneration picture of Thews • Yan picture almost flat to start with, gives slight fall-off with centrality Caution - <pT2> from fits often unreliable for AA (stable when restricted to pT<5 GeV/c here) Better for theoretical comparisons to look at RAA(pT)? nucl-ex/0611020

  36. 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.

  37. 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

  38. (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

  39. Pb-Pb @ 158 GeV NA60 In-In 158 GeVpreliminary SPS J/y suppression • Dissociation by gluons

  40. Dissociation by gluons sDiss • Cross section : g+J/y c + c-bar • LO calculation • Decay width k[GeV] T = 350 MeV, G = 0.8 fm/c

  41. Dissociation by gluons • Cross sectionはLO計算。正しいのか？ • Binding Energyの小さいy’やccに適応可能か？

  42. 5 Pb-Pb @ 158 GeV Successful models (1) • Dissociation by thermal gluons • Based on LO pQCD cross section between J/y (cc) and g R. Rapp PLB92 (2004) 212301 X.N.Wang PLB540 (2002) 62 100 20 40 ET [GeV]

  43. PHENIX – p+p J/ψ – new run6 data • Forward rapidity falloff steeper than 3-gluon pQCD model - black curve [Khoze et al. , Eur. Phys. J. C39, 163-171 (2005)] • Slightly favors flatter shape at mid-rapidity than most models • BR•tot = 178 ± 3 ± 53 ± 18 nb • Harder pT than lower energy & softer at forward rapidity PHENIX - hep-ex/0611020 <pT2> = 3.59±0.06 ±0.16 <pT2> =4.14±0.18 +0.30-0.20

  44. Statistical Model (1) • Statistical Hadronization • 元々のMotivationはSPSで<J/y>/<h>が中心衝突度に依存しない事。Hadron生成量は統計Modelで記述できる。 • Hadronの生成量 • もうひとつのパラメター：gu,d,s,c(Fugacity) • u,d,s,c quarkがどれほど化学平衡に達しているかという指標 • 実際のYield = g x ni

  45. Statistical Model (2) • RHICではgs~ 1 (SPSでは、gs<0.7) • Strange quarkがようやく平衡状態 • Charm quarkは重い。殆どがHiggs Mass • 衝突初期にしか出来ない。 • ＱＧＰ中での熱的生成量(exp-(2mc/Tc)) ~ 10-7 • なのに、平衡状態を仮定して、J/yのＹｉｅｌｄを計算 • gcが平衡状態からのずれを担う。 cc-bar cross section (experiment, FONLL) Model Input: Nccdir, T, m, Volume このModelはp+p, Au+AuにおけるCharm Productionに大きく依存する。

  46. Statistical Model (3) • Charm Production Cross sectionによる大きな不確定性がある。 • NNLO pQCD計算 ds/dy = 63.7+95.6-42.3mb • ds/dy = 123 mb (PHENIX) • 2倍程度、大きい。 • CDFが測定したCharm Cross • SectionもNNLOより • 1.5倍程度大きい。 NNLO pQCD計算のCharm Cross Sectionでは、よく合っているが、 PHENIXの実験結果では不一致。

  47. Recombination –In medium Formation • Medium中でもJ/y生成。 • Kinetic Formation Model • Transport Model

  48. Recombination –In medium Formation • 問題点と疑問点 • Charm Cross Sectionの大きな不確定性 • p+p, Au+AuにおけるCharm y, pT分布? • QGP中ではCharmはDiffusiveに動いているが、理由はまだ分かっていない。 • J/y+gccbar　のCross Sectionが正しいか？ • ccやy’に対するRecombinationは考えられていない。 • Ncの与え方。どのモデルもNcは時間に対して一定。正しい？ • Charmの熱的生成はない、Charm数は保存。 • DメソンへのRecombinationも考慮すべき。NcNc(t)、tと共に減少するはず。ただ、DメソンとJ/yではFreezeout時間が異なるか？ • J/yの方が圧倒的に早く生成されるなら、正しいかも。 • Naïveには、ccが空間的に近くにないといけない。ccがCoupleするよりも、u,dとCoupleする方が多いはず。 Au+AuにおけるCharm, D, J/y生成 を理解しなければならない。

  49. 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.

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