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

2. 2 M. van Leeuwen, High-p T and jets 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 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. 3 M. van Leeuwen, High-p T and jets Direct  at high-p T T. Isobe p+p year-5 RHIC is accumulating p+p stats 0-10% Au+Au Nuclear effects + E-loss (frag  ) Quark-  in-medium conversions No enhancement in Au+Au Agrees with NLO pQCD

4. 4 M. van Leeuwen, High-p T and jets  0 in p+p, d+Au M. Russcher 2005 p+p STAR gearing up ,  0 in p+p, d+Au Good agreement with NLO pQCD and PHENIX PHENIX, B. Sahlmüller R dA centrality dependence Measures Cronin, initial state effects nucl-ex/0610036

5. 5 M. van Leeuwen, High-p T and jets R AA for  0 : medium density I C. Loizides hep-ph/0608133v2 I. Vitev PHENIX, B. Sahlmüller W. Horowitz Use R AA to extract medium density: I. Vitev: 1000 < dN g /dy < 2000 W. Horowitz: 600 < dN g /dy < 1600 C. Loizides: 6 < < 24 GeV 2 /fm Statistical analysis to make optimal use of data Caveat: R AA folds geometry, energy loss and fragmentation

6. 6 M. van Leeuwen, High-p T and jets What do we learn from R AA ? ~15 GeV  E=15 GeV Energy loss distributions very different for BDMPS and GLV formalisms But R AA similar! Renk, Eskola, hep-ph/0610059 Wicks et al, nucl-th/0512076v2 BDMPS formalism GLV formalism Need more differential probes

7. 7 M. van Leeuwen, High-p T and jets L-dependence I: azimuthal asymmetry PQM: Dainese, Loizides, Paic, Eur Phys J C38, 461 R AA, S loss vs azimuthal angle  L (2) scaling sets in p T > 6-8 GeV v 2 only described by models above p T > 6 GeV nucl-ex/0611007 In Plane Out of Plane LL Au+Au 200GeV 0-10% 50-60% V. Pantuev, D. Winter New scaling parameter L  No significant loss for L  < 2 fm  Formation time effect? V. Pantuev hep-ph/0506095 Describes R AA vs angle down to lower p T

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

9. 9 M. van Leeuwen, High-p T and jets Energy dependence of R AA preliminaryp+C reference 0-12.7% most central Pb+Pb K. Reygers Broad agreement between experiments Lower √s NN, steeper initial spectra More pronounced ‘Cronin’ effect Stronger suppression (same R AA for more dilute medium) NA49 preliminary Central Pb+Pb/Au+Au NA49 PHENIX (  + +  - )/2 -0.3 < y < 0.7 B. Sahlmüller B. Mohanty C. Blume

10. 10 M. van Leeuwen, High-p T and jets   nucl-ex/0504001 Energy dependence of R AA R AA at 4 GeV: smooth evolution with √s NN J. Velkovska Agrees with energy loss models

11. 11 M. van Leeuwen, High-p T and jets Single particle measurements Energy dependence SPS to RHIC 200 GeV System size dependence –p+p and d+Au references –R AA vs N part –R AA vs reaction plane, v 2 Particle type dependence Large set of systematics becoming available Comparisons to theory ongoing Warrants revisiting some areas of theory? (e.g. baryon fragmentation, path length dependence)

12. 12 M. van Leeuwen, High-p T and jets Fragmentation and energy loss I: near-side 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? Components  Near-side jet peak  Near-side ridge  Away-side (and v 2 ) 3 < p t,trigger < 4 GeV p t,assoc. > 2 GeV Au+Au 0-10% preliminary Two distinct questions: Lesson: The near-side jet does interact with the medium M. Calderon, J. Putschke associated  trigger Di-hadron correlations

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

14. 14 M. van Leeuwen, High-p T and jets Subtracting the ridge II STAR, M. Horner C. Zhang Near side increase at low p T,assoc seen by STAR and PHENIX Subtraction of  -independent ‘ridge-yield’ recovers centrality-independent jet yield Vacuum fragmentation after energy loss? Or non-trivial effect hidden by exponential spectra? 1 1 z T = p T,assoc /p T,trig

15. 15 M. van Leeuwen, High-p T and jets p T -dependence of ridge Ridge p T -spectra are ‘bulk-like’ Ridge independent of p T,trigger STAR, J. Putschke Jet spectra Yield (p t,assoc > p t,assoc,cut ) Ridge spectra Yield (p t,assoc > p t,assoc,cut ) p t,assoc,cut

16. 16 M. van Leeuwen, High-p T and jets What is the ridge? A. Majumder, B. Muller, S. Bass 3 2 GeV STAR, J. Putschke  dN/d  hep-ph/0611135 Proposed explanations so far: Ridge shape 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 More differential measurements possible?Jury still outDetailed predictions welcome!

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

18. 18 M. van Leeuwen, High-p T and jets Away-side yields and energy loss C. Zhang M. Horner |  | >  /2 Clear evolution of away-side suppression with p T,trig, p T,assoc Low p T,trig, p T,assoc : enhancement Increase Q 2 for same p T,trig due to energy loss? Caveat: shapes change non-trivially 8< p T trig < 15 GeV, PRL 95, 152301 Preliminary |  | > 0.9

19. 19 M. van Leeuwen, High-p T and jets Di-hadrons: away-side shape Preliminary 2.5 < p T, trig < 4.0 GeV/c 1.0 < p T, assoc < 2.5 GeV/c Clear evolution peripheral → central: Widening, flattening and ‘dip at  ’ nucl-ex/0611019 0-12% 40-60% 0-12% PHENIX: C. Zhang, N. Grau, J. Jia, E. Vazquez STAR, M. Horner High statistics Run IV data

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

21. 21 M. van Leeuwen, High-p T and jets Away-side shape: p T, trig dependence 0-12% 4.0 < p T trig < 6.0 GeV/c 6.0 < p T trig < 10.0 GeV/c 3.0 < p T trig < 4.0 GeV/c Preliminary 0-12% 1.3 < p T assoc < 1.8 GeV/c STAR, M. Horner Away-side flatter for larger p T,trigger But broadening at low p T,assoc persist

22. 22 M. van Leeuwen, High-p T and jets Summary of shape evolution Cu+Cu follows trend vs N part away hump dashed=PHENIX, solid=STAR*0.35 PHENIX, C. Zhang, A. Sickles F. Wang Shape change due to yield increase away from  =  System size dependence N part 1/3

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

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

25. 25 M. van Leeuwen, High-p T and jets 3-particle results Au+Au 0-12% (  12 -  13 )/2 (  12 +  13 )/2-  PHENIX Preliminary C. Pruneau, J. Ulery C. Zhang, N. Ajitanand  13 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  12 Tantalising results! Discussion/comparison of methods between experiments needed 3 < p T, trig < 4 GeV/c 1 < p T, assoc < 2 GeV/c

26. 26 M. van Leeuwen, High-p T and jets 3-particle correlations at SPS Like signUnlike sign CERES, S. Kniege  ti  tj All charge background subtracted 0-5% central 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? 2.5 < p T, trig < 4.0 GeV/c 1.0 < p T, assoc < 2.5 GeV/c Raw signal

27. 27 M. van Leeuwen, High-p T and jets Origin of p/  enhancement: PID correlations Preliminary Near side Away side Baryon/meson assoc B/M singles Trigger h ± : 2.5 < p T < 4.0GeV/c A. Sickles 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 p T -range desirable

28. 28 M. van Leeuwen, High-p T and jets J. Bielcikova R. C. Hwa et al., nucl-th/0602024  -h correlation Near-side yield similar for , ,  triggered correlations Initial expectation:  dominantly from TTT recombination, no associated yield Revisited (at QM06): possible large contribution from reheated medium Experimental tests pending

29. 29 M. van Leeuwen, High-p T and jets Away-side suppression at high p T NLO Theory talk, H. Z. Zhang J. Jin, N. Grau, J. Jia, H. Pei Data: STAR PRL 95, 152301 T. Renk and Eskola, hep-ph/0610059 Di-hadron suppression: smaller surface bias, potentially better differential probe Comparison to theory ongoing New data: R AA  I AA also in Cu+Cu Emission points Hydro profile

30. 30 M. van Leeuwen, High-p T and jets  -jet measurements J. Jin, M. NguyenS. Chattopadhyay, F. Benedosso First results in p+p Promising results: statistical errors can be reduced in coming runs Consistent with expectations from Pythia Consistent between experiments

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

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

33. 33 M. van Leeuwen, High-p T and jets Future directions  -jet rates R AA at LHC S. Wicks, W. Horowitz T. Renk Slower rise in BDMPS than GLV … and much more! Need plot R AA at LHC not independent of p T : more sensitive to energy loss distribution B. Jacak, W. Vogelsang  -jet at RHIC-II and LHC

34. 34 M. van Leeuwen, High-p T and jets Thank you For your attention And to all who provided input and discussion to shape this talk!