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Jet Correlations at RHIC

Jet Correlations at RHIC. Jets from p+p and d+Au collisions Jets in Au+Au collisions High-p T jets: higher p T reach over Run-2 (2002) Low-p T jets: Exploration of the shape modification Cornucopia of other, newer avenues

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Jet Correlations at RHIC

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  1. Jet Correlations at RHIC • Jets from p+p and d+Au collisions • Jets in Au+Au collisions • High-pT jets: higher pT reach over Run-2 (2002) • Low-pT jets: Exploration of the shape modification • Cornucopia of other, newer avenues • Is there a consistent picture of jet evolution from two-particle correlations in HIC? Nathan Grau, Iowa State University N. Grau Columbia University 10/17/05

  2. Phys. Rev. Lett. 91, 241803 (2003) p-pp0 + x p-pprompt + x data vs pQCD KKP Kretzer A Baseline for HIC Collisions: p+p NLO pQCD reproduces the measured single p0 production and prompt photons. Prompt photons – not from hadron decay N. Grau Columbia University 10/17/05

  3. PHENIX range A Surprise that pQCD Works? J. Owens CTEQ 2004 PHENIX measures at a similar xT ranges as Fermilab and finds good agreement with pQCD. Implication: no extra kT. kT: Transverse momentum of partons from confinement, gluon radiation at h=0 N. Grau Columbia University 10/17/05

  4. L. Apanasevich PRD 59 074007 (1999) kT for an Experimentalist • kT: Net pair pT • Experimentally determined by • Drell-Yan • Di-jet acoplanarity • Di-(prompt) photon correlations • Modified by initial and final state gluon radiation • Drell-Yan only initial state • Di-jets initial and final state N. Grau Columbia University 10/17/05

  5. Importance of kT for HIC • Jets good probe of QGP • Strong interaction with final state • Survives hadronization of the QGP • Sensitive to early times of the collision • Useful probe for multiple scattering/Energy Loss • Multiple collisions prior to hard scattering (Cronin effect) • Energy loss from gluon bremsstrahlung, multiple scattering, etc. N. Grau Columbia University 10/17/05

  6. Df Jet Measurement by Two-Particle Azimuthal Correlations Mixed events – corrects pair acceptance Total Elliptic flow C(Df) Near-angle Df = 0, jet Far-angle Df = p, di-jet Sum over all events  jets measured on a statistical basis Hard scattering Resonance decays Df (rad) N. Grau Columbia University 10/17/05

  7. pQCD & Two-Particle Correlations • Inclusive singles distributions described by pQCD • p+p baseline calibrated for single inclusive spectra • Jet rates are well calibrated • Correlations include non-perturbative effects • kT is partly due to confinement • fragmentation is non-perturbative • No curves overlay p+p correlation functions N. Grau Columbia University 10/17/05

  8. Correlations in p+p and d+Au N. Grau Columbia University 10/17/05

  9. = 21 GeV = 27.4 GeV p+A E683 E609 Strong Broadening at Lower Energies g+A and p+A offset due to an effect from jet reconstruction All data agree point-to-point when offset taken into account. A1/3 dependence in the g+A and p+A. Strong nuclear dependence on kT. A factor of 2 increase between p+p to p+Au at lower energy N. Grau Columbia University 10/17/05

  10. nucl-ex/0510021 Trigger 4-6 GeV/c PRL 91, 072304 (2003) Trigger 5-10 GeV/c Jet Correlations Resultsin p+p and d+Au Assume an isotropic background and two Gaussian distributions for the jet peaks. Extract the width of the Gaussian jet peaks. N. Grau Columbia University 10/17/05

  11. Jet Acoplanarity Difference Between p+p and d+Au J. Qiu, I. Vitev PLB 570 161 (2003) p0 – crosses p+/- – circles Multiple scattering model not inconsistent with the data. N. Grau Columbia University 10/17/05

  12. Why No Significant Difference Between p+p and d+Au? • “Intrinsic” kT larger than the kT due to multiple scattering. • Could it be recombination (Hwa and Yang)? • Shower (fragmented) partons recombining with the soft (radiated) background • Initially predicted factor of 2 increase in the near angle yield (R. Hwa, C.B. Yang: PRC 70,054902 (2004)) N. Grau Columbia University 10/17/05

  13. Ratio to p+p Hwa and Tan, nucl-th/0503060 Data favors no increased yield above p+p, but not inconsistent with reco Associated Particle Yields Trigger 5-10 GeV/c Measured yield in the gaussian near angle jet function N. Grau Columbia University 10/17/05

  14. Conclusions About Hard Scattering in d+Au Collisions • Two-particle correlations: d+Au like p+p • Lack of acoplanarity increase • Yields and acoplanarity are consistent with multiple scattering picture • And consistent with (modified) recombination picture. • Conclusion: Need more data. N. Grau Columbia University 10/17/05

  15. Au+Au Collisions Prior to QM2005 PRL 90 (2003) 082302 nucl-ex/0507004 Trigger 4-6 GeV/c Trigger 2.5-4 GeV/c N. Grau Columbia University 10/17/05

  16. Away-side Jet Modificationat High-pT in A+A N. Grau Columbia University 10/17/05

  17. Away-Side Jet at High pT STAR Preliminary H. Pei QM2005 poster D. Magestro QM2005 Trigger h 8-15 Associated h > 2 Above 7 GeV/c the (Gaussian?) away-side jet is evident. The beginning of jet tomography… N. Grau Columbia University 10/17/05

  18. Away-Side Widths From E-Loss I. Vitev hep-ph/0501255 IAA IAA Black – scattering of parent partons Red – gluons from energy loss. Able to fit IAA from STAR. N. Grau Columbia University 10/17/05

  19. Trigger 5-10 GeV/c J. Jin QM2005 poster 8 < pT(trig) < 15 GeV/c Extracted Away-Side Jet Widths at High pT Widths do not change between p+p and Au+Au?!? N. Grau Columbia University 10/17/05

  20. 8 < pT(trig) < 15 GeV/c Associated Yield Suppression • Yield decrease smoothly with centrality • IAA (with d+Au denominator) suppression! • Factor of 2 peripheral  central N. Grau Columbia University 10/17/05

  21. Trigger 5-10 GeV/c More on Associated Yields • Associated yields multiplied by a factor to put them on the same scale • Suppression stronger at lower pT • Consistent with flat to a factor of two suppression at highest pT J. Jin QM2005 poster N. Grau Columbia University 10/17/05

  22. Picture of High-pT Jets Very different centrality dependence of these observables. Are these results reconcilable in E-loss picture? What are the implications for jet tomography? N. Grau Columbia University 10/17/05

  23. Non-Gaussian Away-side Shape at Lower pT N. Grau Columbia University 10/17/05

  24. Extracting Jet Correlations in A+A (I) • Assumptions: • Two source model • Elliptic flow • Di-jets • v2 from reaction plane measurements • <v2trigv2assoc> = <v2trig><v2assoc> • Similar assumptions between PHENIX and STAR N. Grau Columbia University 10/17/05

  25. Extracting Jet Correlations in A+A (II) • Extraction of the background level • Absolute normalization • Parameter in the fit of C(Df) • Assume Zero Yield from jets At the Minimum of the C(Df) (ZYAM) • Similar to STAR from disappearance paper. • Typically 1-2% difference between results • but jet S/B few % at low and intermediate pT • Large yield uncertainties, less effect on the shape N. Grau Columbia University 10/17/05

  26. Au+Au Correlations from High to Low pT J. Jia QM2005 Poster ZYAM subtracted, green/blue lines indicate subtraction uncertainty. h-h Most peripheral collisions: Jet is seen for all pT Onset of away-side jet modification in semi-peripheral collisions. Flattening and dip structure at low pT and at high centrality. N. Grau Columbia University 10/17/05

  27. Formation of a Local Minimum J. Jia QM2005 Poster h-h PHENIX preliminary Flat correlation where a harmonic is present. C(Df) strength ~ S/B. N. Grau Columbia University 10/17/05

  28. csQGP= Evidence of Mach Cones STAR Preliminary =+/-1.23=1.91,4.37 J. Casalderrey-Solana, E. ShuryakandD. Teaney hep-ph/0411315 N. Grau Columbia University 10/17/05

  29. Or Cerenkov Radiation Koch, Majumder, Wang nucl-th/0507063 Requires colored bound states (mass m) in medium (temperature T). Strong p-dependence of cone angle N. Grau Columbia University 10/17/05

  30. assoc D trigg D assoc Testing the Splitting Parameterize the away-side shape as a double Gaussian that are offset symmetrically around Df = p by fit parameter D. Could be a “bent” jet or a mach/ Cherenkov cone – no physics assumption made N. Grau Columbia University 10/17/05

  31. Parameterize the Away-Side Shape P. Constantin QM2005 Poster • Smooth increase splitting with centrality • Plateau at most central • Lowest pT correlations systematically above the higher pT correlations. • Possible indication of Cerenkov-like radiation? PHENIX Preliminary N. Grau Columbia University 10/17/05

  32. System Size and Energy Systematics of Away-Side Shape Au+Au @ 62.4 GeV h-h 2.5-4 x 1-2.5 GeV/c PHENIX Preliminary J. Frantz QM2005 poster D is independent of system and energy. Is this reconcilable with Mach or Cerenkov cones? N. Grau Columbia University 10/17/05

  33. Dip Persists at SPS M. Ploskon QM2005 Poster • CERES data at much lower root-s but similar trigger and associated pT ranges • higher xT – quark jet dominated • Background by ZYAM • Correlation is flat at far angles – dip present at SPS at a smaller level! N. Grau Columbia University 10/17/05

  34. Near Side Broadening PHENIX Preliminary A. Kravitz QM2005 Poster Systematic trend of broadening as a function of centrality. First observation of medium effect on the near side. N. Grau Columbia University 10/17/05

  35. Other New/Upcoming/Interesting Jet Correlations N. Grau Columbia University 10/17/05

  36. PHENIX Preliminary Mach cone Simulation Flow+Jet Three-particle Correlations: Mach/Cerenkov Cone • Trigger 2.5-4 GeV/c • Two associated particles 1-2.5 GeV/c • Choose specific reaction plane bin such that v2trig = 0 • Contains correlations between the associated particles N. Grau Columbia University 10/17/05

  37. Reaction Plane Dependence: Path Length Dependence Red– 6Green – 5Blue – 4Light Blue – 2Pink – 1 Black - Integral J. Jia QM2005 Poster Require the trigger particle within a given RP orientation Flow varies in a particular way J. Bielcikova et al Phys. Rev. C69:021901, 2004 N. Grau Columbia University 10/17/05

  38. Electron Triggered Correlations:Heavy Quark Energy Loss 1-4 GeV/c F. Matathias QM2005 Poster Use jet correlations to further understand heavy quark energy loss. N. Grau Columbia University 10/17/05

  39. g Hadrons Direct-g Triggered Correlations: Holy Grail of Energy Loss Studies PRL 94 232301 (2005) Direct photons not suppressed in the medium. N. Grau Columbia University 10/17/05

  40. C(Df) C(Df) Df Df Inclusive g-h Correlations in Au+Au J. Jin QM2005 Poster g: 5-10 GeV/c h: 1-2 GeV/c g: 5-10 GeV/c h: 3-5 GeV/c Comparison with p0 triggered data necessary to extract direct photon correlations. N. Grau Columbia University 10/17/05

  41. Conclusions • d+Au jets look like p+p jets. • Multiple scattering small • Jets at high pT in Au+Au collisions • Show no away-side width broadening • Show suppression of away-side yields • Jets at low pT Au+Au: strong shape modifications • Due to a medium? Effect at lower root-s and different systems. • What properties can we extract? cs, n, etc. • More results to come • Three-particle correlations, reaction plane dependence, heavy flavor tagging • Prompt-g-jet correlations! N. Grau Columbia University 10/17/05

  42. Backup Slides N. Grau Columbia University 10/17/05

  43. PRL 91, 072303 (2003) Cronin Effect in Single Inclusive Particle Production in d+Au PRL 91, 072304 (2003) • Enhancement at mid-pT • Meson-Baryon difference • Look for jet acoplanarity in d+Au vs p+p N. Grau Columbia University 10/17/05

  44. Open: p+p, Closed: d+Au Triggers p0p+/- Jet Acoplanarity in p+p and d+Au Independent Fragmentation Model: N. Grau Columbia University 10/17/05

  45. Fragmentation Functions Scaled z at high trigger pT. N. Grau Columbia University 10/17/05

  46. d+Au p+p dN/dxE Scaling PHENIX Preliminary PHENIX Preliminary p+p and d+Au are similar N. Grau Columbia University 10/17/05

  47. a L1 L2 L1 c L2 b L1 L2 Unchanging Jet Widths: Possible Implications A. Dainese et al, EJPC 38 (2005) 461 • Away-side jet fragments in vacuum and parent parton unaffected by medium? • Tangential jets? • Suppressed production area/volume of the colliding region • Inconsistent with inclusive RAA • Punch throughs • Little E-loss/multiple scattering N. Grau Columbia University 10/17/05

  48. Lack of Near Side Broadening at High pT At higher pT, no increase with centrality Consistent with the picture of production at the corona. N. Grau Columbia University 10/17/05

  49. Reaction Plane Dependence at Higher pT High trigger pT High associated pT N. Grau Columbia University 10/17/05

  50. RP Dependence of Near Angle Widths Near angle widths are flat as a function of reaction plane – still consistent with production at the corona N. Grau Columbia University 10/17/05

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