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Jets and high-p T results from QM 2006

Jets and high-p T results from QM 2006. Marco van Leeuwen, LBNL. Motivation. A reminder. Use jets and high-p T particles to probe the medium. Initial production at high-p T is calculable in perturbative QCD and can be calibrated by reference measurements. Goal: measure medium properties

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Jets and high-p T results from QM 2006

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  1. Jets and high-pT results from QM 2006 Marco van Leeuwen, LBNL

  2. Motivation A reminder Use jets and high-pT particles to probe the medium Initial production at high-pT is calculable in perturbative QCD and can be calibrated by reference measurements • Goal: measure medium properties • Density, temperature Number of degrees of freedom • Dynamical properties e.g. viscosity • However, we still need to calibrate our probe: • Fragmentation, hadronisation in the vacuum • … and in the medium • Calibrate/constrain energy loss mechanism • Check initial production rates

  3. Direct g at high-pT T. Isobe 0-10% Au+Au Nuclear effects + E-loss (frag g) p+p year-5 Quark-gin-medium conversions RHIC is accumulating p+p stats Agrees with NLO pQCD No enhancement in Au+Au

  4. 0in p+p, d+Au M. Russcher RdA centrality dependence PHENIX, B. Sahlmüller nucl-ex/0610036 2005 p+p Measures Cronin, initial state effects STAR gearing up g, p0 in p+p, d+Au Good agreement with NLO pQCD and PHENIX

  5. RAA for p0: medium density I PHENIX, B. Sahlmüller I. Vitev C. Loizides hep-ph/0608133v2 W. Horowitz Use RAA to extract medium density: I. Vitev: 1000 < dNg/dy < 2000 W. Horowitz: 600 < dNg/dy < 1600 C. Loizides: 6 < < 24 GeV2/fm Statistical analysis to make optimal use of data Caveat: RAA folds geometry, energy loss and fragmentation

  6. What do we learn from RAA? GLV formalism BDMPS formalism ~15 GeV Wicks et al, nucl-th/0512076v2 Renk, Eskola, hep-ph/0610059 DE=15 GeV Energy loss distributions very different for BDMPS and GLV formalisms But RAA similar! Need more differential probes

  7. L-dependence I: azimuthal asymmetry New scaling parameter Le Describes RAA vs angle down to lower pT Le 50-60% No significant loss for Le < 2 fm  Formation time effect? V. Pantuev hep-ph/0506095 V. Pantuev, D. Winter 0-10% PQM: Dainese, Loizides, Paic, Eur Phys J C38, 461 RAA, Sloss vs azimuthal angle Au+Au 200GeV Out of Plane In Plane nucl-ex/0611007 rL(2) scaling sets in pT > 6-8 GeV v2 only described by models above pT> 6 GeV

  8. Quark vs gluon from quark energy loss STAR, L. Ruan STAR, B. Mohanty p/p Curves: X-N. Wang et al PRC70(2004) 031901 PRL 97, 152301 (2006) 90% of p from gluons 40% of p from gluons pT (GeV/c) No sign of stronger gluon energy loss in p/p or p/p ratios Medium modifications to FF? X.N. Wang and X.F. Guo, NPA 696, 788 (2001) W. Liu, C.M. Ko, B.W. Zhang, nucl-th/0607047 Need new calculations, with better baryon FF (AKK)

  9. Energy dependence of RAA 0-12.7% most central Pb+Pb B. Sahlmüller Central Pb+Pb/Au+Au (+ + -)/2 -0.3 < y < 0.7 K. Reygers NA49 preliminary C. Blume NA49 p+C reference preliminary PHENIX Broad agreement between experiments • Lower √sNN, steeper initial spectra • More pronounced ‘Cronin’ effect • Stronger suppression (same RAA for more dilute medium) B. Mohanty

  10. Energy dependence of RAA J. Velkovska p 0 nucl-ex/0504001 RAA at 4 GeV: smooth evolution with √sNN Agrees with energy loss models

  11. Single particle measurements Large set of systematics becoming available • Energy dependenceSPS to RHIC 200 GeV • System size dependence • p+p and d+Au references • RAA vs Npart • RAA vs reaction plane, v2 • Particle type dependence Comparisons to theory ongoing Warrants revisiting some areas of theory?(e.g. baryon fragmentation, path length dependence)

  12. Fragmentation and energy loss I: near-side Dj trigger Di-hadron correlations • What is it ? ‘something’ coupling to long flow ? Can this quantify E-loss ? • How to deal with it?Need to subtract for near-side studies? associated 3 < pt,trigger < 4 GeV pt,assoc. > 2 GeV Au+Au 0-10% preliminary Components • Near-side jet peak • Near-side ridge • Away-side (and v2) Two distinct questions: M. Calderon, J. Putschke Lesson: The near-side jet does interact with the medium

  13. Ridge phenomenology Jet + Ridge Jet Jet + Ridge nucl-ex/0611016 J. Bielcikova PHENIX, A. Sickles PHENIX: drop in baryon-triggered yield for most central events Ridge observed for all trigger particle types After subtraction: jet-yield independent of centrality

  14. Subtracting the ridge II STAR, M. Horner zT = pT,assoc/pT,trig 1 C. Zhang Near side increase at low pT,assoc seen by STAR and PHENIX C. Zhang Subtraction of Dh-independent ‘ridge-yield’ recovers centrality-independent jet yield 1 Vacuum fragmentation after energy loss? Or non-trivial effect hidden by exponential spectra?

  15. pT-dependence of ridge Ridge spectra Jet spectra STAR, J. Putschke Yield (pt,assoc > pt,assoc,cut) Yield (pt,assoc > pt,assoc,cut) pt,assoc,cut pt,assoc,cut Ridge pT-spectra are ‘bulk-like’ Ridge independent of pT,trigger

  16. What is the ridge? Ridge shape STAR, J. Putschke dN/dDh A. Majumder, B. Muller, S. Bass • Radiated gluons, broadened by • Longitudinal flow, Armesto et al, PRL 93 (2004) • QCD magnetic fields, Majumder et al, hep-ph/0611035 • Medium heating + recombination,Chiu & Hwa PRC72, 034903 • Radial flow + trigger bias, Voloshin nucl-th/0312065, Nucl. Phys. A749, 287 hep-ph/0611135 3 < pt,trigger < 4, pt,assoc. > 2 GeV Dh Proposed explanations so far: Jury still out More differential measurements possible? Detailed predictions welcome!

  17. Energy content of Ridge } “Ridge energy” } “Ridge energy” STAR, Phys. Rev. Lett. 95 (2005) 15230 J. Putschke talk 4 < pt,trigger < 6 GeV 6 < pt,trigger < 10 GeV 0.15 < pt,assoc < 4 GeV Near-side modification in published results also due to ridge Energy content of ridge: few GeV

  18. Away-side yields and energy loss Preliminary M. Horner C. Zhang |Dj| > 0.9 8< pTtrig < 15 GeV, PRL 95, 152301 |Dj| > p/2 Clear evolution of away-side suppression with pT,trig, pT,assoc Low pT,trig, pT,assoc: enhancement Increase Q2 for same pT,trig due to energy loss? Caveat: shapes change non-trivially

  19. Di-hadrons: away-side shape Preliminary PHENIX: C. Zhang, N. Grau, J. Jia, E. Vazquez 40-60% 2.5 < pT,trig < 4.0 GeV/c 1.0 < pT,assoc < 2.5 GeV/c nucl-ex/0611019 STAR, M. Horner 0-12% High statistics Run IV data 0-12% Clear evolution peripheral → central: Widening, flattening and ‘dip at p’

  20. Away-side shape: energy dependence 2.5 < pT,trig < 4.0 GeV/c 1.0 < pT,assoc < 2.5 GeV/c PHENIX, C. Zhang Similar trends seen at lower √s=62.4 GeV at RHIC nucl-ex/0611019 CERES, S. Kniege 0-5% 10-20% And at SPS Is this still jet-fragmentation? Compare p+p?

  21. Away-side shape: pT,trig dependence Preliminary 3.0 < pTtrig < 4.0 GeV/c 4.0 < pTtrig < 6.0 GeV/c 6.0 < pTtrig < 10.0 GeV/c 1.3 < pTassoc < 1.8 GeV/c STAR, M. Horner 0-12% 0-12% Away-side flatter for larger pT,trigger But broadening at low pT,assoc persist

  22. Summary of shape evolution dashed=PHENIX, solid=STAR*0.35 away hump System size dependence F. Wang PHENIX, C. Zhang, A. Sickles Npart1/3 Cu+Cu follows trend vs Npart Shape change due to yield increase away from Dj=p

  23. Interpretations of away-side broadening Gluon rad+Sudakov Mach Cone/Shock wave Cherenkov radiation T. Renk, J. Ruppert V. Koch, A. Majumder, X-N. Wang A. Polosa, C. Salgado Stöcker, Casseldery-Solana et al Also: Vitev, Phys. Lett. B630 (2005) Or large kT from radial flow or energy loss Fries, Armesto et al, Hwa Many explanations possible, need more input to conclude

  24. 3-particle correlations Event by event deflection of jets Cone like structure in each event   13 13   0   0   12 12 3-particle Dj-Dj probes away-side structure: Distinguish event-by-event deflection vs conical (Mercedes) emission pattern However: Large backgrounds, background shapes not simple

  25. 3-particle results C. Pruneau, J. Ulery C. Zhang, N. Ajitanand 13 12 3 < pT,trig < 4 GeV/c 1 < pT,assoc < 2 GeV/c Au+Au 0-12% PHENIX Preliminary (12+13)/2- (12-13)/2 Cumulant analysis: Model-independent Non-zero 3-particle structure Jet+background analysis: Model-dependent, more sensitive Off-diagonal peaks consistent with conical emission Different co-ordinates: No ‘deflected-jet peak’ consistent with conical emission Tantalising results! Discussion/comparison of methods between experiments needed

  26. 3-particle correlations at SPS Dfti Dftj Like sign Unlike sign Raw signal CERES, S. Kniege Raw signal 2.5 < pT,trig < 4.0 GeV/c 1.0 < pT,assoc < 2.5 GeV/c 0-5% central All charge background subtracted Strong charge-dependence seen in raw signal Baryon density effect? Off-diagonal peaks seen after background subtraction Indicative of conical emission Mach cones at SPS? Some other mechanism?

  27. Origin of p/p enhancement: PID correlations Away side Near side A. Sickles Preliminary Preliminary Baryon/meson assoc Baryon/meson assoc B/M singles Trigger h±: 2.5 < pT < 4.0GeV/c Near side: increase with centrality Measure particle composition of ridge? Away-side B/M increases strongly with centrality Need comparisons to theory for interpretation Extended pT -range desirable

  28. L,X,W-h correlation J. Bielcikova Near-side yield similar for L, X, W triggered correlations Initial expectation: W dominantly from TTT recombination, no associated yield R. C. Hwa et al., nucl-th/0602024 Revisited (at QM06): possible large contribution from reheated medium Experimental tests pending

  29. Away-side suppression at high pT Theory talk, H. Z. Zhang Emission pointsHydro profile NLO Data: STAR PRL 95, 152301 Di-hadron suppression: smaller surface bias, potentially better differential probe J. Jin, N. Grau, J. Jia, H. Pei T. Renk and Eskola, hep-ph/0610059 Comparison to theory ongoing New data: RAA IAA also in Cu+Cu

  30. g-jet measurements J. Jin, M. Nguyen S. Chattopadhyay, F. Benedosso First results in p+p Consistent with expectations from Pythia Consistent between experiments Promising results: statistical errors can be reduced in coming runs

  31. g-jet in Au+Au Dj distribution Yields J. Jin, M. Nguyen Goal: Measure g-jet suppression in A+A Monochromatic source: differential measurement of jet-quenching X.-N. Wang, Z. Huang, PRC 55:3047, F. Arleo et al JEHP 0411, 009, T. Renk, PRC 71, 034906 First results in Au+Au: consistent with suppression But large statistical uncertainties Upcoming RHIC run will improve statistics for this measurement

  32. Summary/outlook • Impressive amount of new data • Extending pT-reach for inclusives • System size, energy dependence mapped out • Detailed shapes/yields at low, intermediate pT Will this constrain energy loss models? Some open questions: 1) Intermediate pT: origin of ridge and away-side broadening 2) Role of baryon fragmentation vs coalescence(quark/gluon energy loss) Expect developments in near future: Baryon/meson fragmentation at higher pT Improve on g-jet measurements

  33. Future directions g-jet rates RAA at LHC B. Jacak, W. Vogelsang T. Renk Need plot S. Wicks, W. Horowitz RAA at LHC not independent of pT: more sensitive to energy loss distribution Slower rise in BDMPS than GLV g-jet at RHIC-II and LHC … and much more!

  34. Thank you For your attention And to all who provided input and discussion to shape this talk!

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