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Jet and Heavy Flavor Probes of Hot QCD Matter

Jet and Heavy Flavor Probes of Hot QCD Matter. Peter Jacobs, LBNL. Calibrated in p+p and p/d+A. Calculable final state medium effects. Why hard probes? (= perturbative processes). Calculable interactions of energetic partons with the medium  calibrated, penetrating tomographic probes.

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Jet and Heavy Flavor Probes of Hot QCD Matter

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  1. Jet and Heavy Flavor Probes of Hot QCD Matter Peter Jacobs, LBNL Jets and Heavy Flavors

  2. Calibrated in p+p and p/d+A Calculable final state medium effects Why hard probes? (= perturbative processes) • Calculable interactions of energetic partonswith the medium •  calibrated, penetrating tomographic probes Jets and Heavy Flavors

  3. Outline • jet quenching and radiative energy loss • inclusive hadron suppression • heavy quark suppression • dihadron correlations: modification of jet structure • outlook to the LHC • (not discussed: quarkonium) Most up-to-date reference: http://hp2006.lbl.gov/source/program.htm Jets and Heavy Flavors

  4. Inclusive jets p0 pQCD in p+p at RHIC Good agreement with NLO pQCD  pQCD should be broadly applicable at RHIC (e.g. heavy flavor production…) Jets and Heavy Flavors

  5. pT (GeV) Inclusive hadron spectra in 200 GeV Au+Au PHENIX PHOBOS Jets and Heavy Flavors

  6. p+p Binary collision scaling Jet quenching I: hadrons are suppressed, photons are not Jets and Heavy Flavors

  7. trigger ? 4< pTtrig < 6 GeV pTassoc > 2 GeV pTassoc > 0.15 GeV recoil cos(Df) STAR, Phys Rev Lett 91, 072304 STAR, Phys Rev Lett 95, 152301 Jet quenching II: recoiling jets are strongly modified I & II: conclusive evidence for large partonic energy loss (“jet quenching”) in dense QCD matter Jets and Heavy Flavors

  8. Transport coefficient: Radiative energy loss in QCD Baier, Schiff and Zakharov, AnnRevNuclPartSci 50, 37 (2000) BDMPS approximation: multiple soft collisions in a medium of static color charges Medium-induced gluon radiation spectrum: Total medium-induced energy loss: DE independent of parton energy (finite kinematics DE~log(E)) DE  L2 due to interference effects (expanding medium DE~L) Jets and Heavy Flavors

  9. Extracting qhat from hadron suppression data RAA: qhat~5-15 GeV2/fm Jets and Heavy Flavors

  10. ~RHIC data QGP Hadronic matter  R. Baier, Nucl Phys A715, 209c What does measure? • Equilibrated gluon gas: • number density ~T3 • energy density e~T4 qhat+modelling  energy density Model uncertainties • pQCD result: c~2 (aS? quark dof? …) • sQGP (multiplicities+hydro): c~10 Jets and Heavy Flavors

  11. Salgado and Wiedemann PRD68 (2003) 014008 Medium-induced radiation spectrum GLV BDMPS   BDMPS(ASW) vs. GLV Baier, Dokshitzer, Mueller, Peigne, Schiff, Armesto, Salgado, Wiedemann, Gyulassy, Levai, Vitev Rough correspondence: (Wiedemann, HP2006)  30-50 x cold matter density Jets and Heavy Flavors

  12. Alternatively: AdS/CFT Liu, Rajagopal and Wiedemann hep-ph/0605178 Rajagopal, HP2006 Jets and Heavy Flavors

  13. RAA only provides lower bound on The limitations of RAA Jets and Heavy Flavors

  14. Eskola et al., hep-ph/0406319 RAA~0.2-0.3 for broad range of ? Inclusive hadrons and surface bias Large energy loss  opaque core Inclusive measurementsinsensitive to opacity of bulk More differential observables are needed to probe deeper… Jets and Heavy Flavors

  15. Heavy quark energy loss Q • In vacuum, gluon radiation suppressed at q < mQ/EQ • “dead cone” effect: heavy quarks fragment hard into heavy mesons Dokshitzer, Khoze, Troyan, JPG 17 (1991) 1602. Dokshitzer and Kharzeev, PLB 519 (2001) 199. Dead cone also implies lower heavy quark energy lossin matter:(Dokshitzer-Kharzeev, 2001) Jets and Heavy Flavors

  16. Origin of surviving jets (radial propagation only) RAA jets go thataway  Heavy quarks are “grey probes” Wicks, Horowitz, Djordjevic and Gyulassy, nucl-th/0512076 • Heirarchy of “surface bias” correlated with opacity/suppression •  differential probes of the medium Jets and Heavy Flavors

  17. S.Wicks et al., nucl-th/0512076 Armesto et al., Phys.Lett.B637:362-366,2006 Heavy flavor suppression via b,ce+X RAA(non-photonic electrons) ~ 0.2 ~ RAA(p0) !! • Gluon density/qhat constrained by light quark supression+entropy density (multiplicity) •  under-predicts electron suppression •  charm vs beauty?elastic energy loss?…? Jets and Heavy Flavors

  18. S.Wicks et al., nucl-th/0512076 RAA b vs c suppression • pT~5 GeV/c: ce suppression ~0.2 •  puzzle resolved if c e dominates non-photonic electron spectrum - is that permissible? Jets and Heavy Flavors

  19. D0 ~factor 2 CDF, PRL 91, 241804 (2003) M. Cacciari, Hard Probes STAR, nucl-ex/0607012 FONLL N. P. electrons in p+p vs FONLL State of the art: Fixed-OrderNext-to-LeadingLog Tevatron charm and beauty vs FONLL:OK • RHIC n.p. electrons: factor 3-5 excess(!) • Large ambiguity in relative contribution of ce/be •  need to resolve b and c explicitly Jets and Heavy Flavors

  20. S.Wicks et al., nucl-th/0512076 Elastic (collisional) energy loss revisited • Elastic DE comparable to Radiative DE – not negligible • Elastic DE important even for light quarks •  revisit energy density estimates? Jets and Heavy Flavors

  21. Resolution of non-photonic electron suppression puzzle needs • experiment: explicit measurement of c vs b suppression • theory: unified framework incorporating both elastic and radiative energy loss Jets and Heavy Flavors

  22. trigger Jet structure via hadron correlations p+p  dijet Full jet reconstruction in the heavy ion environment is difficult  probe jet structure via dihadron correlations Phys Rev Lett 90, 082302 Jets and Heavy Flavors

  23. pTassoc > 0.15 GeV cos(Df) STAR, Phys Rev Lett 95, 152301 Established results… 4< pTtrig < 6 GeV pTassoc > 2 GeV STAR, Phys Rev Lett 91, 072304 Jets and Heavy Flavors

  24. trigger Yield per trigger pTtrigger>8 GeV/c ? recoil STAR, nucl-ex/0604018 Dihadron correlations at higher pT Recoil jet clearly seen above background but at suppressed rate differential measurement of`DE  upper bound on qhat? Jets and Heavy Flavors

  25. D(zT) Recoiling hadron distribution p Df Recoiling hadrons: details No modification of fragmentation No angular broadening STAR, nucl-ex/0604018 Recoil rate is suppressed but jet features unmodified  see only non-interacting jets? Jets and Heavy Flavors

  26. Trigger direction STAR preliminary Df High pT dihadrons: detailed dynamical calculation T. Renk, hep-ph/0602045 Different geometrical biases underly trigger and recoil distributions ~75% of recoils due to non-interacting jets All bremsstrahlung models: discrete term Jets and Heavy Flavors

  27. Various models of bulk expansion T. Renk, HP2006 T. Renk, hep-ph/0602045 Correlations and dynamics (cont’d) • Calculation ~reproduces recoil yields with params fit to RAA • additional sensitivity to dynamics of the collision? (in progress…) • Suggestive calculation • need larger dynamic range in pTtrig and pTassoc to probe energy loss (not only discrete term) Ultimately: g+jet (experimentally challenging, in progress) Jets and Heavy Flavors

  28. near away PHENIX, QM05 and nucl-ex/0507004 STAR, Phys Rev Lett 95, 152301 Leading hadrons Medium Medium response to jet energy loss I Look at low pT recoils… • experimentally challenging to discriminate signal/bkgd • new development: 3-particle correlations • Mach cone, Cerenkov radiation,…? Jets and Heavy Flavors

  29. 3<pt,trigger<4 GeV pt,assoc.>2 GeV Au+Au 0-10% preliminary Armesto et al, nucl-ex/0405301 Medium response to jet energy loss II Near-side “ridge” correlated with jet trigger Dh Df Induced radiation dragged by longitudinally expanding fluid? Jets and Heavy Flavors

  30. Jet quenching at the LHC • Pb+Pb at 5.5 TeV: • First ion collisions 2008 • qualitatively new probes •  full (~unbiased) jet reconstruction in HI events Jets and Heavy Flavors

  31. Summary • Experiment • jet quenching is well-established: multiple strong effects • key open issue: how does the medium respond to DE? • second generation of high precision measurements: • heavy flavor, correlations, g+jet • RHIC upgrades (charm reco), high luminosity (g+jet) • LHC brings qualitatively new physics • Theory • qualitative but not yet quantitative understanding of jet quenching • significant uncertainties in • underlying mechanism (elastic vs radiative) • heavy quark production • modeling of dynamical evolution Jets and Heavy Flavors

  32. Final comment • Current theoretical uncertainties present the largest barrier to quantitative understanding and full exploitation of RHIC and LHC Heavy Ion measurements • The situation is analogous to the early days of the Solar Neutrino puzzle: • We need a Standard Solar Model for Ultra-relativistic Heavy Ion physics • (The good news: this is in progress) Jets and Heavy Flavors

  33. Extra slides Jets and Heavy Flavors

  34. Prob. distributions for parton to lose DE parton with E<0.5 GeV is absorbed by medium Further limitation of RAA Can RAA of light quarks/gluons constrain the energy loss distribution? T. Renk (HP2006): accurate geometry/expansion, toy models for P(DE) • Can always tune medium density to reproduce RAA: •  only weak constraint on e-loss distribution More differential observables are needed to probe deeper… Jets and Heavy Flavors

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