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Production of Hadrons Correlated to Jets in High Energy Heavy-Ion Collisions

Production of Hadrons Correlated to Jets in High Energy Heavy-Ion Collisions. Charles Chiu Center for Particles and Fields University of Texas at Austin. Shangdong University, Jinan, Shangdong, June 8, 2009. Outline. An overview on hadrons production in high energy heavy ion collisions

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Production of Hadrons Correlated to Jets in High Energy Heavy-Ion Collisions

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  1. Production of Hadrons Correlated to Jets in High Energy Heavy-Ion Collisions Charles Chiu Center for Particles and Fields University of Texas at Austin Shangdong University, Jinan, Shangdong, June 8, 2009

  2. Outline • An overview on hadrons production in high energy heavy ion collisions • Transverse flow of theQuark-Gluon matter • Jet-medium interactions • Ridge phenomena, and the correlated emission model (CEM) • Summary

  3. 1.Overview on hadron production in heavy ion collisions From Bevalac to RHIC, and to LHC Bevalac:U with 2 GeV/N on U-target AGS-RHIC: Au+Au WNN=200GeV SPS-LHC: Pb+Pb WNN=5.5TeV

  4. STAR Collaboration BrazilRussia Universidade de Sao Paolo MEPHI – Moscow LPP/LHE JINR - Dubna China IHEP-Protvino IHEP - Beijing USTC - Hefei IMP - Lanzhou SINR - Shanghai Tsinghua University IPP - Wuhan U.S. Labs Argonne National Laboratory EnglandBrookhaven National Laboratory University of Birmingham Lawrence Berkeley National Laboratory FranceU.S. Universities IReS Strasbourg UC Berkeley / SSL SUBATECH - Nantes UC Davis UC Los Angeles GermanyCarnegie Mellon University MPI – Munich Creighton University University of Frankfurt Indiana University Kent State University India Michigan State University IOP - Bhubaneswar City College of New York VECC - Calcutta Ohio State University Panjab University Penn. State University University of Rajasthan Purdue University Jammu University Rice University IIT - Bombay University of Texas - Austin Texas A&M University Poland University of Washington Warsaw University of Technology Wayne State University Yale University 419 collaborators 44 institutions 9 countries

  5. Energy range on cosmological scale

  6. Sorenson, Winterworshop 08

  7. d/dNch vs Nch Au + Au sNN = 200 GeV Nch: # of charged pcles in an event b: Distance between 2 centers Npart: # of participating NN pairs “Centrality”: Area-bins from right to left. b

  8. Outgoing particle: Kinematic labels pT y x f q Pseudorapidity  = ln( cot q/2 ) Transverse mom pT Azimuthal angle f 8

  9. 2. Transverse flow of theQuark-Gluon matter Is Quark-Gluon matter really produced in HIC? • If it is, particles produced should not be incoherent superposition of those from NN collisions. • The hadronic matter should be regarded as a macro-system of its own. Expect a collective behavior following up the explosion. • Observation of transverse flow signals that the macro-system has been formed. • radial flow • elliptic flow

  10. Evidence on radial flow pT-distribution: ~exp[-pT/T*] Shuryak 04 • Light pcle: T*=TgT • Massive: T*~mvT • As A increases, • the line becomes steeper • collective flow becomes more pronounced PbPb, A=208 sNN~25GeV T* SS, A=32, pp

  11. Blast Wave Model AA-collision Central Intermediate Peripheral pp-collision p, K, N Spectra (STAR) Each Nch-bin is fitted by freeze-out:Tkin & flow speed: b In the central region collective flow speed reaches 0.6.

  12. Heinz05, A review Hydrodynamic-model Relativistic hydro-equations of ideal fluid Conserv. of local baryon number, energy and momentum , leads to ( with ) (1) (2) Here cs is the speed of sound, with • Decrease of nB and e due to local expansion • Acceleration is due to local pressure gradient

  13. f v2 a measure momentum anisotropy V2 = [ <px2> -<py2>] / [ <px2> +<py2>]=< cos2>, dN/d = dN/d(0o)[ 1 +V2 cos2+ …] y y x x Spatial anisotropy momentum anisotropy

  14. Elliptic Flow Kolb, Sollfrank, Heinz Equal energy density lines

  15. Hydro model: pT dependence. Kolb&Rapp03 • Model describs pT spectra of various species & centralities • Decoupling temperature assumed, 165MeV (blue), 100 MeV (red). • Early thermal equilibrium: t0~0.6 f/c is used.

  16. midrapidity : |h| < 1.0 STAR Model PRL 86 (2001) 402 Peripheral  Central Comparison between hydro-model and the v2 data STAR PRL87 (2001)182301 Centrality dependence: Overall agreement, except near peripheral region where model prediction v2 is larger than data. PT-curves for pions and protons are confirmed by the data. More accurate kaon data are needed.

  17. 3. Jets-medium interactions Jet quenching Nuclear Mod. factor Large pT suppression is highly suppressed in Au+Au vs in d+Au. Suppression extends to all accessible pT. Away side jet: Suppressed in Au+Au Presence in p+p and in d+Au. Trigger x Away-side jet suppressed

  18. Ridge phenomena:2-particle correlation STARdata. Putschke, QM06 dN/dDh vs Dh R: Plateau, J: Peak Differences: trig. and assoc Dh=htrig-hassoc Df=ftrig-fassoc Central: 3 < pTtrig< 4 GeV, pTassoc > 2 GeV 18

  19. Hwa 08CC, Hwa, Yang 08 A ridge model without early therm equilib. • Assume many semi-hard jets (2-3 GeV) are produced near the surface of the initial almond. • Jets-medium interaction generates a layer of enhanced thermal partons. They are the ridge particles, R. • The bulk thermal medium background, B is isotropic. • Total thermal partons yield: F f F v2(pT,b) is determined based on phenomenological properties of B(pT) and R(pT)

  20. Comparison between the ridge model and the v2 data Recombination model: ET up to 5 GeV. Pions: Include TT, TS, SS Protons: TTT, TTS, TSS V2: Protons V2: Pions ET<1, TT only.

  21. Trigger Azimuth dependence Feng, STAR (QM08) Feature: For 20-60% the yield decreases rapidly with fs. y Assoc Trigger f fs x 3 < pTtrig< 4 GeV; 1.5 < pTassoc< 2 GeV Beam

  22. 4. Correlated emission model (CEM) A scenario on the ridge formation CC, Hwa 09 y • A semi-hard collision at P. One parton exits as trigger, the other absorbed by the medium. • Exit parton traverses through the medium, accompanied by soft radiations. • Absorption of radiation energy locally energizes the thermal partons • Enhanced thermal partons carried by the flow. Theylead to the formation of ridge particles. trigger x P(x0,y0) x flow

  23. Trigger direction vs flow direction Matched case |fs –y|~0: Enhanced thermal partons flow in the same direction, leading to strong ridge. x Mismatched case |fs – y|~900 : Enhanced thermal partons dispersed over a wide range of f-- weak ridge. Local flow along y (green) Trigger along fs (red)

  24. Ridge yield at f with trigger fs due to interaction at x0,y0 Ridge yield per trigger(including all pts) fs (x0,y0) t Interaction at one point:(x0, y0) • P(x0, y0, t): Probability parton traverses t and emerges as a trigger. t’ f G C y y fs t’

  25. Comparison with the data CEM fit to the fs data • Parameters: • Thickness of interaction layer is ~ RA/4 • Gaussian-width of fs-y cone ~200. Normallized to fit one point at lowest fs for 0-5%. 25

  26. Comparison with  data in 20-60% region Left panel Shift of the peak from Df=0: ~40% b=0 out in • Matched “In”-region (Df<0) is larger at ~40% • Mismatched “out”-region (Df>0) is smaller at ~40% shift Df= f -fs

  27. Model predictions Asymmetry vs fs Df curves: The left-shift in the peak position as a function of fs. 27

  28. R-yield vs b (or Npart) at various fs We predict decrease of yield/trigger as b is decreased at small fs 28

  29. 5.Summary • Some well known features are: • Experimental evidence of transverse collective flows • Hydrodynamic model has been success in predicting pT spectrum and v2 data at least up to 1GeV • There are strong jet-medium interactions, and the medium strongly absorptive. • More recent discovery of Ridge phenomenon is discussed. • Ridge particles are generated in jet-medium interaction. They are the enhanced thermal partons. • CEM assumes there is strong correlation between the trigger direction and the flow direction. • Phenomenological application and further test of the model are presented.

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