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

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 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 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/

5 M. van Leeuwen, High-p T and jets R AA for  0 : medium density I C. Loizides hep-ph/ v2 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 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/ Wicks et al, nucl-th/ v2 BDMPS formalism GLV formalism Need more differential probes

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/ 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/ Describes R AA vs angle down to lower p T

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/ Medium modifications to FF? STAR, L. Ruan PRL 97, (2006) Curves: X-N. Wang et al PRC70(2004) 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 M. van Leeuwen, High-p T and jets Energy dependence of R AA preliminaryp+C reference % 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 (  + +  - )/ < y < 0.7 B. Sahlmüller B. Mohanty C. Blume

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

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 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 M. van Leeuwen, High-p T and jets Ridge phenomenology nucl-ex/ 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 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 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 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/ 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/ Medium heating + recombination, Chiu & Hwa PRC72, Radial flow + trigger bias, Voloshin nucl-th/ , Nucl. Phys. A749, 287 More differential measurements possible?Jury still outDetailed predictions welcome!

17 M. van Leeuwen, High-p T and jets Energy content of Ridge STAR, Phys. Rev. Lett. 95 (2005) < 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 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, Preliminary |  | > 0.9

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/ % 40-60% 0-12% PHENIX: C. Zhang, N. Grau, J. Jia, E. Vazquez STAR, M. Horner High statistics Run IV data

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/ < 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 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 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 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 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 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 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 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 M. van Leeuwen, High-p T and jets J. Bielcikova R. C. Hwa et al., nucl-th/  -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 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, T. Renk and Eskola, hep-ph/ 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 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 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,

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 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 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!