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The Quenching of Beauty Last Hope for a Grey Probe of the QGP

The Quenching of Beauty Last Hope for a Grey Probe of the QGP. James Dunlop Brookhaven National Laboratory. The Promise of Jet Tomography. Simplest way to establish the properties of a system Calibrated probe Calibrated interaction Suppression pattern tells about density profile

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The Quenching of Beauty Last Hope for a Grey Probe of the QGP

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  1. The Quenching of BeautyLast Hope for a Grey Probe of the QGP James Dunlop Brookhaven National Laboratory Heavy Quark Workshop, Berkeley

  2. The Promise of Jet Tomography • Simplest way to establish the properties of a system • Calibrated probe • Calibrated interaction • Suppression pattern tells about density profile • Heavy ion collisions • Hard processes serve as calibrated probe • Suppression provides density measure + = Heavy Quark Workshop, Berkeley

  3. Central RAA Data Increasing density The Limitations of RAA: “Fragility” K.J. Eskola, H. Honkanken, C.A. Salgado, U.A. Wiedemann, Nucl. Phys. A747 (2005) 511 Surface bias leads effectively to saturation of RAA with density Challenge: Increase sensitivity to the density of the medium A. Dainese, C. Loizides, G. Paic, Eur. Phys. J. C38(2005) 461 Heavy Quark Workshop, Berkeley

  4. Black and White S.S. Adler et al, Phys. Rev. Lett. 94, 232301 (2005) • Medium extremely black to hadrons, limiting sensitivity to density • Medium transparent to photons (white): no sensitivity • Is there something grey? Heavy Quark Workshop, Berkeley

  5. Calibrated Interaction? Grey Probes Wicks et al, Nucl. Phys. A784 (2007) 426 • Problem: interaction with the medium so strong that information lost: “Black” • Significant differences between predicted RAA, depending on the probe • Experimental possibility: recover sensitivity to the properties of the medium by varying the probe Heavy Quark Workshop, Berkeley

  6. 200 GeV p+p Gluons vs Quarks: Method • q jets or g jets gluon jet contribution to protons is significantly larger than to pions at high pT in p+p collisions at RHIC; pbar/ < 0.1 from quark jet fragmentation at low beam energy .STAR Collaboration, PLB 637, 161 (2006). • From Kretzer fragmentation function, the g/q jet contribution is similar to AKK. S. Kretzer, PRD 62, 054001 (2000). Heavy Quark Workshop, Berkeley

  7. Gluons vs. Quarks: No shade of gray • Gluons should lose more energy than quarks • Pions have larger quark contribution than protons • SO, Protons should be more suppressed than pions • Experimentally NOT observed: equal suppression for pT>6 GeV/c • Perhaps: If medium already black to quarks, can’t be blacker than black • Other methods to be tried: kinematics in h (as done in e.g. dijet Sivers) gluon jet quark jet quark jet STAR Collaboration, PRL 97 (152301) 2006 Heavy Quark Workshop, Berkeley

  8. Charm/Beauty: No shade of gray PHENIX, PRL 98 (2007) 172301 STAR, PRL 98 (2007) 192301 • Unexpectedly strong suppression of non-photonic electrons a major issue • Calls into question the calibration of the interaction of the probe with the medium • Uncertainties in B contribution: need to measure c and b separately Heavy Quark Workshop, Berkeley

  9. Mechanisms for Energy Loss “Passage of Particles through Matter”, Particle Data Book • QED: different momenta, different mechanisms • Just beginning the exploration of this space inQCD Bremsstrahlung Radiative dE/dx Heavy Quark Workshop, Berkeley

  10. Calibrated Probe? Electrons in p+p STAR, PRL 98 (2007) 192301 • Large uncertainties in non-photonic electrons, even in p+p • STAR and PHENIX factor of 2 discrepancy in measurements • STAR: runs 8 and 9 low material (same as PHENIX), PHENIX…? • Theoretical uncertainties, esp. in b vs. c contribution • Need to measure c and b separately, in all systems, with precision b Crossing from c to b: anywhere from 3-10 GeV c Heavy Quark Workshop, Berkeley

  11. Correlations • WMAP: 10-5 level • One sample • Only photons • Well-defined separation of sources • RHIC: 10-1 to 10-3 level • Multiple samples • Multiple probes • Model dependence in separation of sources • quite a few “two-component” models, with different components Heavy Quark Workshop, Berkeley

  12. + c g e- K- g c e D0 D*0 B- c c b g g b B+ D0 g g - K+ Heavy Flavor Correlations Isolate b from c Isolate production mechanism In medium: what is losing energy, and how much? Flavor creation  gluon splitting/fragmentation 0 Heavy Quark Workshop, Berkeley

  13. e-h from B e-h from D Fit Correlations: Can we tell how much beauty? Xiaoyan Lin, QM2006 • Use e-h Correlation • Large B mass compared to D • Semileptonic decay: e gets larger kick from B. • Broadened e-h correlation on near-side. • Extract B contribution • Use PYTHIA shapes • Con: Model dependent • Pro: Depends on decay kinematics well described • Fit ratio B/(B+D) • There is more information from correlations that is not currently being used (momentum, charge, etc.) Heavy Quark Workshop, Berkeley

  14. B contribution to NP electrons vs. pT Xiaoyan Lin, QM2006 • Fit e-h correlation with PYTHIA Ds and Bs • Non-zero B contribution • Contribution consistent with FONLL • Model dependent (PYTHIA) • Depends mainly on kinematics of D/B decay (not Fragmentation) • Dominant systematic uncertainty: • photonic background rejection efficiency • Additional uncertainties under study • There is more information from correlations that is not currently being used p+p 200 GeV Heavy Quark Workshop, Berkeley

  15. Future at RHIC: “RHIC II” or the fb era STAR HFT Current Au Run, year 7 • RHIC: luminosity + upgraded detectors for precision • Beauty: last hope for a “grey” probe; needs detector upgrades to both STAR and PHENIX to isolate from charm • g-jet: precision probe of energy loss • Upsilon: precision tests of Debye screening with a “standard candle” Previous Au Run, year 4 PHENIX VTX One year at RHIC II ~ 30 nb-1 30 nb-1*1972 =~ 1 fb-1 p+p equivalent Heavy Quark Workshop, Berkeley

  16. Grey Correlations: Heavy Flavor in the fb era Heavy flavor Light Hadrons Identified heavy flavor correlations: promising, but statistical power still low RHIC II: many orders of magnitude (>~x1000 with luminosity, S/B improvements) Inclusive Spectra Correlations From 5 pb-1 Heavy Quark Workshop, Berkeley

  17. Quarkonium: Upsilon RHIC Sequential dissociation of quarkonia to measure energy density of plasma Requires full luminosity of RHIC II for definitive measurements Proof of principle measurement: run 6 p+p Upsilon(1S+2S+3S)→e+e- Heavy Quark Workshop, Berkeley

  18. Other initiatives: Muons and dileptons • Muon Tracking Detector: use magnet steel as absorber • Physics: dileptons from intermediate mass up to quarkonia states • Best method for separating Upsilon states (a la CDF) • R+D stage: Brookhaven LDRD 2007-2008 • Dielectrons using TOF for ID and HFT for background rejection Heavy Quark Workshop, Berkeley

  19. Conclusion Idunn’s Apples of Youth, D’Alair’s Book of Norse Mythology Watershed in coming years from RHIC II luminosity and detector upgrades • Precision studies with g, b, c, and associated multi-hadron correlations • IF beauty is less suppressed than other parton species, we will be able to probe the properties of the QGP with exquisite precision Is Beauty Grey? We need more apples to tell Heavy Quark Workshop, Berkeley

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