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Perspectives on Quarkonia Physics at RHIC II

Perspectives on Quarkonia Physics at RHIC II. Thomas Ullrich, BNL Yale University, April 16-17, 2004 Workshop on RHIC-II Physics and Perspectives for New Comprehensive Detector. The Original Idea …. Matsui & Satz (PLB 178 (1986) 416 J/  suppression by QGP

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Perspectives on Quarkonia Physics at RHIC II

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  1. Perspectives on Quarkonia Physics at RHIC II Thomas Ullrich, BNL Yale University, April 16-17, 2004 Workshop on RHIC-II Physics and Perspectives for New Comprehensive Detector

  2. The Original Idea … Matsui & Satz (PLB 178 (1986) 416 J/ suppression by QGP Color screening of static potential between heavy quarks:

  3. The Original Idea … Matsui & Satz (PLB 178 (1986) 416 J/ suppression by QGP Color screening of static potential between heavy quarks: D. Kharzeev and H. Satz, Phys. Lett. B477 (2000): Hard gluons needed for breaking J/ not available in hadron gas S. Digal et al., Phys. Rev. D 64, 094015 (2001) C.-Y. Wong, Phys. Rev. C 65, 034902 (2002) Calculations using lattice potentials: sequential suppression ’, c dissolves below TC J/ dissolves at 1.2 TC

  4. … and its Confirmation … • CERN/SPS s  17 GeV • mid-rapidity • large statistics (beyond RHIC)

  5. … Experimental Status 2004 … • Study pA in detail  absorption in nuclear matter Ebinding(Y’) ~ 50 MeV Ebinding(c) ~ 200 MeV Ebinding(J/Y) ~ 640 MeV

  6. … Experimental Status 2004 … • Detailed pA studies  absorption in nuclear matter • Study trigger (ET) • wiggle is gone • suppression w.r.t. normal • nuclear absorption remains

  7. … and Evolving Theories … A. Capella, D. Sousa, nucl-th/0303055 A.P.Kostyuk, M.I. Gorenstein, H. Stocker, W. Greiner, Phys. Lett B 531, 195-202 • Various alternative models which also reproduce data: • Statistical coalescence model (also needs enhanced open charm) • Absorption by comoving matter

  8. E866 J/Y data Quark shadowing and final state absorption + Gluon shadowing + Anti-shadowing + dE/dx Remaining Questions … • Charm production at SPS ? • Feeddown from c states ? • xF dependence ? • important means to constrain theory • and understand nuclear effects • and learn about production mechanism

  9. … and the Big Blow … • QM2004 F. Karsch “News from Lattice QCD” Free energy of a thermal medium due to the presence of static quark-antiquark pairs F itself often interpreted as heavy quark potential at finite T and used in model calculations – but: change in entropy needs to be taken into account (F = E - TS) Energy and entropy contributions to F at differentqq separations important. The r-dependent entropy contribution makes a direct use of F in potential models questionable.

  10. … and the Big Blow ? J/Y dissociates for 1.6 TC < T < 1.9 TC rather abrupt disappearance of J/Y J/Y gradually disappears for T > 1.5 TC J/Y strength reduced by 25% at T = 2.25 TC

  11. Now What ? “The charmonium ground state (J/Y) persist in the QGP as well defined resonances with no significant change in their zero temperature masses at least up to T ~ 1.5 Tc,gradually disappear for T > 1.5 Tc and are gone at 3 Tc.” F. Karsch, hep-lat/0403016 But: Used Maximum Entropy Method still needs further studies … So far the width is not calculated (only position and amplitude) Width is likely to increase  Dima: J/Y still can dissolve in a short time (1 fm/c) at RHIC F. Karsch (QM2004): Entire charmonium discussion was based on lattice calculations in quenched QCD. We need a much larger computer to do better! QCD on Lattice (2-flavor): Phase transition at: TC≈ 1738 MeV, eC≈ (62) T 4≈ 0.70  0.27 GeV/fm3 RHIC: Lattice: e/T4 ~ 10  95 GeV/fm3 for 3TC ~ 520 MeV 6GeV/fm3 for 1.5TC At RHIC energies, central Au+Au collisions: From Bjorken estimates via ET and Nche > 5 GeV/fm3 Calculations of energy loss of high-pT particles e ≈ 15 GeV/fm3 Hydro models assuming thermalization give ecenter ≈ 25 GeV/fm3

  12. Quarkonium Studies in HEP … • Tevatron (s = 1.8 TeV) • CDF: huge improvement from run II • J/Y,  cross-section down to pT=0 • Polarization measurement of J/Y, Y’,  soon • c contribution measured • still all in |y|<0.4 (0.6) Solve puzzle from fixed target: low polarization for Y(1S) but high for Y(2S), Y(3S) J/Y (1S) (2S) (3S)

  13. Quarkonium Studies in HEP … • Tevatron (s = 1.8 TeV) • D0: • s for |y| < 1.8 ! • J/Y, Y’, c1, c2 • (1S,2S,3S) Summer 2002 Results 4.8 pb-1 of data ~30% systematic uncertainty Luminosity: 114 pb -1

  14. Quarkonium Studies in HEP … • Hera-B • pA (s=42 GeV) • J/Y / Y’ production ratios • pT, xF = -0.4 – 0.1, cos* differential distributions • c/ J/Y ratio • Belle, BaBar • e+e- cccc puzzle: s(eeccY)/s(eeXY)  0.6 • B  X(3872) K (cJ(2P),D*D molecular state, …) • question the success of NRQCD

  15. Quarkonium Studies in HEP … • There is a large community (HEP) studying quarkonia to a large degree • tremendous flow of new results and excellent measurements • currently more issues raised than answered  makes it interesting • Production is well measured but theoretically not understood (as is charm production in general) • The good old octet-model is in question • NRQCD ? • At high s (CDF/D0) heavy quark production mechanism might be different from that at lower s • are results from Tevatron relevant for RHIC energies? • There’s a huge gap for studies of charmonia in hadronic collisions between fixed target (38 GeV and 1.8 TeV) RHIC is right in between

  16. Quarkonium Measurements at RHIC • AA • the major goal: suppression as signature of QGP • Thermometer for early state: Tdiss(Y’) < Tdiss((3S)) < Tdiss(J/Y)  Tdiss((2S))< Tdiss((1S)) • pp • Interesting in itself • no nuclear effects (production pure) • close s gap (fixed target  CDF,D0) • needed as baseline for pA, AA • Spin: DG via J/Y • pA • needed to study nuclear effects • Rate of rare processes increased by Aa compared to pp

  17. AA at RHIC • For a full understanding of charmonium suppression: • understand nuclear effects • absorption, shadowing • from pA compared to pp • important: xF, x1, x2 dependence • suppression vs. recombination • pT, centrality dependence • contribution from feeddown ( states) • measure at a minimum in pA • understand co-mover absorption •  less affected • centrality, reaction plane, and pT dependence • need to understand charm production • Ultimate measurement (dream?): v2, suppression vs. reaction plane

  18. Need Good Open Charm Measurement SPS s = 17 GeV RHIC s = 200 GeV At RHIC open charm production provides reference and may be the only mean to understand charmonium suppression (same gluon conditions in the initial stage)

  19. Quarkonium Measurements • Golden decay mode: • Y(1S, 2S), (1S, 2S)  ℓ+ ℓ- • c J/Y + g, b  + g • m+m- • clean trigger • experiments have usually higher statistics than e+e- • not the best when low pT is important • e+e- • trigger hard for J/Y (no problem for ) • larger background than m+m-

  20. Requirements for 3rd Generation Detector • High Rate • Large acceptance  rate + xF coverage Pythia 6.2 Pythia 6.2

  21. Requirements for 3rd Generation Detector • High Mass Resolution (close to CDF) • Efficient Trigger ( Level-2) CDF  m+ m- Tracking chamber in 1.4 T field resolution 8.5 ‰ @ 4.9 GeV PRL 75 (1995) 4358

  22. Requirements for 3rd Generation Detector •   J/Y() + g measurements require: • highly granular E.M Calorimeter at least at mid-rapidity • probably only feasible in pp, pA, peripheral AA • need simulations here • large acceptance • Reduce hadronic background • high e/h possible with good calorimetry and PID up to 10-20 GeV/c • situation better for muons anyhow • Good measure of reaction plane • easy with ZDC+SMD

  23. Rates at RHIC-II Assume here: • large acceptance (|h|<3) • one channel only (e+e- or m+m-) • RHIC-II: • L = 5·1032 cm-2 s-1 (pp) • L = 7-9·1027 cm-2 s-1 = 7-9 mb-1 s-1 (AuAu) • hadr. min bias: 7200 mb 8 mb-1 s-1 = 58 kHz • 30 weeks, 50% efficiency  Ldt = 80 nb-1 • 100% reconstruction efficiency • sAA = spp (AB)a

  24. Rates at RHIC-II • Au+Au min bias rates • R(J/Y) = 27 Hz • R(Y’) = 1 Hz • R((1S)) = 0.01701 Hz • R((2S)) = 0.00297 Hz • R((3S)) = 0.00324 Hz • Au+Au, 30 weeks, 50% efficiency • 2.7·108 J/Y • 1·107 Y’ • 170100 (1S) • 29700 (2S) • 32400 (3S) • pp • loose factor (AB)a • gain Lpp/LAA ~ 60,000

  25. Summary • In terms of quarkonia physics RHIC-II is not too far behind LHC • s(LHC)/s(RHIC) = 9 (GRV-HO) – 25 (MRS-D1) • RHIC-II: 5  higher L • RHIC: > 5 times longer running • Measuring “just” J/Y is not enough to extract a physically meaningful result  AA, pp, pA as function of pT, xF, cos*, centrality, reaction plane • Given a 3rd generation detector and RHIC-II luminosity allow a world class measurement in pp, pA, AA • Enough statistics to allow the study of production vs. pT, xF, cos*, centrality, reaction plane • Quarkonia in polarized pp might open a whole new opportunity unique to RHIC (I know too little about it for this talk)

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