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Correlations for Jet Probes of Quark-Gluon Plasma

leading particle. hadrons. q. q. hadrons. leading particle. Correlations for Jet Probes of Quark-Gluon Plasma. Olga Evdokimov University of Illinois at Chicago. (some). RHIC Discoveries. Strongly interacting medium with partonic degrees of freedom Strong collective flow

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Correlations for Jet Probes of Quark-Gluon Plasma

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  1. leading particle hadrons q q hadrons leading particle Correlations for Jet Probes of Quark-Gluon Plasma Olga Evdokimov University of Illinois at Chicago

  2. (some) RHIC Discoveries • Strongly interacting medium with partonic degrees of freedom • Strong collective flow • Constituent number scaling • Jet quenching • “Missing” high-pT hadrons • Novel “landscape” in hadron correlations NNPSS 2011

  3. R Elliptic flow is developed at early stage Time Elliptic Flow  Fourier expansion for angular distributions: … v2 - elliptic flow Initial state spatial anisotropy  Pressure gradient anisotropy  Final state momentum anisotropy NNPSS 2011

  4. Hydro model Perfect Fluid • v2(pt) and mass dependence - best described by ideal hydrodynamics! • Ideal hydro  “Perfect” liquid: • equilibrium, zero mean free path, low viscosity Note: strange, multi-strange, charm hadrons -- flow! NNPSS 2011

  5. Partonic Degrees of Freedom Baryons Pressure gradients converting work into kinetic energy Mesons v2 appears to scale with the number of constituent quarks.  Quark coalescence NNPSS 2011

  6. X-ray source Hard Probes for QGP Idea - use calibrated external probes to study medium properties l Strongly-interacting perfect fluid with partonic degrees of freedom Courtesy of J. Klay For HI collisions  use self-generated (in)medium probes  Hard probes (jets)! NNPSS 2011

  7. Hard parton scattering leading particle hadrons q q hadrons leading particle Hard Probes “Hard” == large scale  suitable for perturbative QCD calculations high momentum transfer Q2 high transverse momentum pT high mass m perturbative Hard probes = PDF  pQCD  FF non-perturbative non-perturbative Assumptions: Factorization assumed between the perturbative and non-perturbative parts Universal fragmentation and parton distribution functions NNPSS 2011

  8. F. Simon p+p→p0+X p+p→p0+X hadrons leading particle S.S. Adler et al, PRL 91 241803 q q hadrons leading particle The reference Simon, private communication KKP: B. Kniehl, G. Kramer, P¨otter, Nucl. Phys. B597, 337 (2001) AKK: S. Albino, B Kniehl, G. Kramer, arXiv: 0803.2768v2 DSS: D. de Florian, W. Vogelsang, F. Wagner, arXiv: 0708.3060v3 NNPSS 2011

  9. leading particle hadrons q q hadrons leading particle Medium properties via jets • Jet Tomography: calibrated (?) probes What happens if partons traverse a high energy density colored medium? • Energy loss mechanisms • Path length effects  non-trivial: • Flavor/color-charge dependence of parton-medium coupling • In-medium fragmentation/ hadronization Hard probes! NNPSS 2011

  10. CDF PRD 65, 072005, 2002. Define “hard” In pp: inclusive cross-section is dominated by jet production above ~4 GeV/c What about RHIC/LHC matter? Probably, > 6GeV/c (but soft part cannot be dropped) NNPSS 2011

  11. QGP101-Jets are quenched ALICE PLB 696 (2011) 30-39 PHENIX p0 @ 200 GeV Nuclear Modification Factors • Jet quenching evident in strong suppression of high pT hadrons • Multiple models provide a successful descriptions of the suppression levels • Most include radiative and collisional energy loss coll rad rad+coll Fits: G. Qin et al, PRL100:072301, 2008 NNPSS 2011

  12. leading particle hadrons q q hadrons leading particle Jets are quenched! How? More differential measurements: • Angular di- and multi-hadron correlations • Reconstructed jets • Jet-jet, jet-hadron correlations Outline: • Early di-hadron correlation results • Landscape details: “peaks”, “humps” and “ridges” • Multi-particle correlations NNPSS 2011

  13. HI collisions: the environment Jet event in Au+Au? Jet event in e+e- Data: High multiplicities → background levels → new techniques for jet studies Physics: Strongly-interacting partonic medium → modified jets NNPSS 2011

  14. Jets via angular correlations leading particle “trigger” Jet produces high pT particles  Select a high pT particle to locate jet, look for correlated hadrons. Measure reference, look for changes: • Correlation strength • Correlated shapes • Associated spectral distributions Df=0 Same-side Df= Away-side NNPSS 2011

  15. But… A fly in the ointment – “backgrounds”: many processes would lead to some sort of angular correlations An example: decomposing autocorrelations from p+p: Correlation measure: NNPSS 2011

  16. Signal decomposition Triggered di-hadron correlations: Two-component model: all hadrons come from jet fragmentation + “soft” processes In two-component approach one needs to know only B, and v2(pT) and assume Azimuthal pair distribution per trigger: common partonic hard-scattering pairs from all other sources NNPSS 2011

  17. First results • Signature two-particle correlation result: • “Disappearance” of the away-side jet in central Au+Au collisions • (for associated hadrons pTassoc>2) • Effect vanishes in peripheral/d+Au collisions Significant Energy Loss in the Medium PRL 91 (2003) 072304 NNPSS 2011

  18. d+Au Au+Au 20-40% Au+Au 0-5% 1/NtrigdN/d(Df) Are there jets? STAR PRL 97 (2006) 162301 8 < pTtrig < 15 GeV/c, pTassoc>6 GeV/c 4<pTtrig<6 GeV/c 2<pTassoc<pTtrig • Recovering the away side: • Away-side yield suppression • Little modification of the Near-side yields • No broadening on Near- or Away-sides NNPSS 2011

  19. Near > High-pT – vacuum fragmentation? STAR PRL 97 (2006) 162301 • Near-side: • No dependence on zT in the measured range – no modification • Away side: • Suppression ~ level of RAA • No dependence on zT in the measured range – no modification NNPSS 2011

  20. assoc. trig2 trig1 Di-jets through correlations Use back-to-back (correlated) trigger pairs to pick both sides of a di-jet “2+1” correlations: Trig1 - highest pT in event, 5-10 GeV/c Trig2 - back-to-back with Trig1pT > 4 GeV/c Associated particles pT > 1.5 GeV/c NNPSS 2011

  21. Di-jet correlations 5 < pTTrig1< 10 GeV/c 4< pTTrig2 < pTTrig1 1.5 < pTAssoc < 10GeV/c STAR K. KauderQM’09 NNPSS 2011

  22. Surface effects in di-jets 200 GeV Au+Au and d+Au STAR PRC (2011) same-side away-side associated particle pT spectra • No evidence of medium modifications Di-jets observed - all tangential? NNPSS 2011

  23. PHENIX Jet modifications: pT  3<pTtrig<4 GeV/c 1.3<pTassoc<1.8GeV/c 1.0 GeV/c < pTassoc STAR M. v Leeuwen, Hangzhou ‘06 PHENIX PRL 97, 052301 (2006). • One high-pT, one low-pT trigger • Reappearance of the away-side jet • Double-hump structure hints at additional physics phenomena NNPSS 2011

  24. trigger Event 1 Event 2 Away side: double-humps trigger trigger pTtrig=3-4 GeV/c, pTassoc=1-2.5 GeV/c Df p -1 1 0 Jet deflection Mach-cone Shock wave Double-humps or shoulders Are these features “real”, e.g. jet-related? NNPSS 2011

  25. trigger Df2 p p Event 1 Event 2 Df2=f2-ftrig 0 0 Df1= f1-ftrig Df1 0 p 0 p 3-particle correlation in D trigger trigger Jet deflection Mach-cone Shock wave NNPSS 2011

  26. d+Au Au+Au central 3-particle- correlations STAR PRL 102 52302 (2009) • Experimental observations consistent with • jet deflection • conical emission (Constrains the speed of sound: • qM= 1.37 ± 0.02 ± 0.06 cS~ 0.2) Closing the chapter? NNPSS 2011

  27. Same-side excess yield PHENIX PRC 78, 014901 (2008) • Excess yield on the same-side • Away-side “shoulders” magnitude  • Is it related to energy loss? • Correlated with same-side excess? Increasing trigger pT  Zooming in on the same side NNPSS 2011

  28. d+Au Au+Au Dh Df RHIC Signature Result: the Ridge • Near-side correlation structure: • Central Au+Au: cone-like + ridge-like • Ridge correlated with jet direction • Approximately independent of Dh and trigger pT NNPSS 2011

  29. Ridge in AA collisions at LHC Pb+Pb @ 2.76 TeV ptT 4-6, paT2-4, 0-5% • Long-range near-side correlation: • Cone-like + ridge-like • Ridge correlated with jet direction • Approximately independent of Dh • and trigger pT NNPSS 2011

  30. 83-94% 55-65% 0-5% 46-55% STAR Preliminary STAR Preliminary STAR Preliminary STAR Preliminary ηΔ width Ridge in pair correlations Au+Au 200 GeV Low pT ridge evolution M Daugherity, QM08 STAR Preliminary STAR Preliminary STAR Preliminary STAR Preliminary Long-range near-side correlation in inclusive events NNPSS 2011

  31. Transverse momentum scan Zoom in on jets: follow pT evolution pT>0.3 GeV/c pT>0.5 GeV/c pT>1.1 GeV/c pT>1.5 GeV/c STAR Preliminary Unlike-charge-sign pairs from 10% most central 200 GeV Cu+Cu data Low pT elongation evolves into high pT ridge NNPSS 2011

  32. 90º 0º in-plane fS=0 out-of-plane fS=90o Path-length effects 3<pTtrig<4GeV/c • Same-side yield • Jet: d+Au ~ Au+Au • Ridge decreases from in-plane to out-of-plane • Flow effects? STAR Preliminary NNPSS 2011

  33. 3-particle correlation in D A2 A1 T : Trigger particle A1: First Associated particle 1=A1-T A2: Second Associated particle 2=A2-T In medium radiation + Longitudinal flow Jet fragmentation in vacuum N.Armesto et.al Phys.Rev.Lett. 93(2004) 242301 Transverse flow boost Turbulent color field. S.A.Voloshin, Phys.Lett.B. 632(2006)490 E.Shuryak, hep-ph:0706.3531 A.Majumder et.al Phys. Rev. Lett.99(2004)042301 NNPSS 2011

  34. R x 3-particle Dh-Dh correlation d+Au 40-80% Au+Au 0-12% Au+Au STAR acceptance |h|<1 PRL105 (2010) 22301 • No significant structures along the diagonals or axes • The ridge is uniform in every event NNPSS 2011

  35. Medium response = Energy loss? “Lumpy” initial conditions in individual events, breaks the symmetry NEXSPHERIO Hydrodynamics Takahashi, et.al. PRL 103,242301 2009 1000 event average No parton-medium coupling required Could explain both double-humps (and ridge) single event NNPSS 2011

  36. Jet-medium interactions or medium flow/fluctuations? v2 v3 • How well measured v2 describes the bulk? • What about high order Fourier harmonics? Full correlation structure described by Fourier Coefficients v1,v2, v3,v4,v5* Central events: v2and v3, are comparable, sizable v4 • Can describe anything with enough terms • vn factorization (?) NNPSS 2011

  37. Summary: • Hard probes are essential for understanding of QGP properties • Angular correlations are powerful experimental tools for such studies High pT Low pT Disappearance of away-side peak in central Au+Au, but not in d+Au ‣ jet quenching discovery ‣ establishing “final” state effect Re-emerging of di-jet signal at higher pT ‣ punch through ? ‣ tangential jets ? Away-side double-hump structure - ‣ mach cone ? ‣ deflected jets ? ‣ medium response/medium? Near-side ridge - ‣ manifestation of energy loss? ‣ medium response/medium ? How to control biases? How to decompose observed structures? NNPSS 2011

  38. Back Up NNPSS 2011

  39. Why QGP? To test and understand QCD: Strong interaction, Confinement, Mass, Chiral symmetry. Few microseconds after the Big Bang the entire Universe was in a QGP state. NNPSS 2011

  40. LatticeQCDprediction Nuclear Matter F. Karsch, hep-lat/0401031 (2004) TC~170  8 MeV~1012 K eC~0.5 GeV/fm3~1012 kg/cm3 QGP What is QGP? QGP a thermally equilibrated deconfined quarks and gluons, where color degrees of freedom become manifest over nuclear, rather than nucleonic, volumes. NNPSS 2011

  41. T Quark-GluonPlasma ~170 MeV r/r0 5-10 Making a Big Bang How to create Quark Gluon Plasma? NNPSS 2011

  42. T Quark-GluonPlasma ~170 MeV r/r0 5-10 Making a Big Bang to create Quark Gluon Plasma (QGP) – a deconfined state of quarks and gluons Heavy Ion Collisions NNPSS 2011

  43. Number of Participants Impact Parameter centrality Collision Centrality Npart= # of participant nucleons Nbin= # of binary collisions (Estimated by Glauber Model) NNPSS 2011

  44. Away-side scan PHENIX PRC 78, 014901 (2008) • Associated pT dependence: • Recovering the away side • Development of “double-humps” or “shoulders” NNPSS 2011

  45. What is same-side ridge? p+p 7 TeV Ridge in high multiplicity p+p at LHC! • Jet modified medium? • Ridge pT-spectra and particle ratios are ‘bulk-like’ • Ridge diminishes(?) with pTtrig • How is it related to jets? NNPSS 2011

  46. peak η width peak amplitude STAR Preliminary STAR Preliminary 200 GeV 62 GeV 83-94% 55-65% 0-5% 46-55% STAR Preliminary STAR Preliminary STAR Preliminary STAR Preliminary Transverse particle density ηΔ width Low pT ridge Low pT ridge evolution M Daugherity, QM08 • Low pT “ridge” – part of “minijet” peak evolution • Sharp transition in both amplitude and width at ρ ~ 2.5 NNPSS 2011

  47. Surface effects in di-jets 200 GeV Au+Au and d+Au STAR PRC (2011) same-side away-side associated particle pT spectra • No evidence of medium modifications Di-jets observed - all tangential? NNPSS 2011

  48. Misbalanced triggers 8 < ETTrig1< 15 GeV/c 4< pTTrig2 < 10 GeV/c 1.5 < pTAssoc < 10GeV/c STAR Preliminary STAR Preliminary STAR H. PeiDNP’09 STAR Preliminary STAR Preliminary NNPSS 2011

  49. NNPSS 2011

  50. PID for Trigger hadrons Inclusive, raw nsp < Cp, pion-depleted sample nsp > Cp, 95% pure pion sample π K P a. u. Au+Au 4< pT,trigger < 6 GeV/c pt,assoc. > 1.5 GeV/c 0-10% central, Trigger is highest pT track NNPSS 2011

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