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Jet Tomography and Particle Correlations in Heavy-Ion Collisions

Jet Tomography and Particle Correlations in Heavy-Ion Collisions. Barbara Betz Thanks to: Miklos Gyulassy , Jorge Noronha, Dirk Rischke , Giorgio Torrieri.

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Jet Tomography and Particle Correlations in Heavy-Ion Collisions

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  1. Jet TomographyandParticleCorrelationsin Heavy-Ion Collisions Barbara Betz Thanks to: MiklosGyulassy, Jorge Noronha, Dirk Rischke, Giorgio Torrieri Phys. Rev. C 79, 034902 (2009);Nucl. Phys. A 830, 777c (2009); Phys.Rev. Lett. 105, 222301 (2010); arXiv:1012.4418 [nucl-th] arXiv:1102.5416 [nucl-th]

  2. HIC Facilities • RHIC, BNL: 2000 – … • p+p, d+Au, Cu+Cu, Au+Au • LHC, CERN: 2008/9 - … • p+p, Pb+Pb • FAIR, GSI: ~2016 - … • acceleratesionsfrom p to U FAIR RHIC LHC hadronic phase and freeze-out initial state expanding fireball ? ? pre-equilibrium hadronization S. Bass, Talk Quark Matter 2001

  3. TomographyandCorrelations STAR, Nucl. Phys. A 774, 129 (2006) • Whatcanbeextractedabout medium proper- • ties? The Medium 4 < pTtrigger < 6 GeV/c 0.15 < pTassoc < 4 GeV/c What do conicalcorrelationstellus? Initial Conditions Whatistherole/impactoffluctuatinginitial conditions? Test sensitivityofazimuthaldependence ofsingleanddihadronnuclearmodification factors PHENIX, Phys. Rev. Lett. 105, 142301 (2010)

  4. 2 Major RHIC Results

  5. Fluid-like Medium Medium behaves like an almost ideal fluid BNL press release, April 18 2005. „dust“ fluid Particles don‘t interact, expansion independent of initial shape Particles interact, expansion determined by density gradient • Reproducing the elliptic flow v2 P. Romatschke and U. Romatschke, Phys. Rev. Lett. 99, 172301 (2007) Data can be described by hydrodynamics with small

  6. 4 < pTtrigger < 6 GeV/c pTassoc > 2 GeV/c STAR, Phys. Rev. Lett. 91 (2003) 072304 Jet Quenching • Like in medicine, hard probes can be used to investigate the medium properties • If created matter is opaque, a jet depositing its energy should eventually disappear jet suppression University Wuppertal, “Schul-Vorlesungen zur Physik” Trigger particle What can the energy lost tell us about the medium properties and the initial conditions?

  7. The Medium

  8. Jets in HIC I Can energy lost by jets tell us something about medium properties? IF the medium behaves like a fluid: Mach cones have to occur because of fluid dynamics Mach cone angle sensitive to EoS • By observation: • Confirm fast thermalization • Study EoS of the fluid

  9. Jets in HIC II • Redistribution of energy to lower pT-particles • Re-appearance of the away-side for low and intermediate pTassoc H. Stöcker, Nucl. Phys. A 750, 121 (2005), J. Casalderrey-Solana et al. Nucl. Phys. A 774, 577 (2006) 4 < pTtrigger < 6 GeV/c 0.15 < pTassoc < 4 GeV/c Au+Au / p+p = 200 GeV STAR, Nucl. Phys. A 774, 129 (2006) PHENIX, Phys. Rev. C 77, 011901 (2008) Reflect interaction of jet with medium

  10. Experimental Studies

  11. Jet - Studies in HIC I Position ofaway-side peaksdoes not change stronglywithpTassoc Not due to Cherenkov gluon radiation What happens to larger pTtrigger? STAR, Phys. Rev. C 82, 024912 (2010) see also PHENIX, Phys. Rev. C 77, 011901 (2008) Many more studies: path-length dependence, centrality dependence, energy dependence A. Sickeles [PHENIX], Eur. Phys. J. C 61, 583 (2009); PHENIX, Phys. Rev. Lett. 97, 052301 (2006); J. Jia, Eur. Phys. J. C 62, 255 (2009)

  12. Some caveats

  13. Background Subtraction D. d’Enterria and BB., Springer Lecture Notes (2008) • Assumption (Two-source model) : • No correlations between flow anisotropy • and jets • ZYAM (Zero Yield At Minimum) • Subtraction of: • estimated elliptic flow modulated • background • can leads to: • double peaked structure Howcanoneproof/disproof thetwo-source model? Background: Particle correlation from elliptic flow Other methods A. Sickles et al, Phys. Rev. C 81, 014908 (2010) J. Ulery [STAR], PoS LHC07, 036 (2007) STAR, arXiv: 1102.2669 [nucl-ex]

  14. 3-Particle Correlations ptrigT=3 – 4 GeV, passocT=1 – 2 GeV • Three-particle correlations seem to corroborate Mach cone idea • What’s the effect of ZYAM? • No agreement with 3-particle cumulant method C. Pruneau, Phys. Rev. C 79, 044907 (2009) J. Ulery [STAR], Int. J. Mod. Phys. E 16, 2005 (2007) Deflected jet Mach Cone ptrigT>3 GeV, passocT=1 – 2 GeV C. Pruneau, Talk at the Workshop on ‘Critical Asessment of Theory and Experiment on Correlations at RHIC’, BNL, February 2009

  15. Theoretical Approach

  16. STAR, Phys. Rev. Lett. 95, 152301 (2005) • Conversion into particles Freeze-out: Modelling of Jets • Medium created in a HIC can be described using hydrodynamics Jets can be modelled using (ideal) hydrodynamics: residue of energy and momentum given by the jet . e+p v • Assumption of • isochronous/isothermal freeze-out • No interaction afterwards mainly flow driven

  17. The Static Medium

  18. Stopped Jet I Applying a static medium and an ideal Gas EoS for massless gluons Maximal fluid response Assume: Near-side jet is not modified by medium BB et al., Phys. Rev. C 79, 034902 (2009) Jet decelerating from v=0.999 according to Bethe-Bloch formalism Bragg Peak a=-1.36 GeV/fm adjusts path length Simplest back-reaction from the medium

  19. Stopped Jet II t=4.5/v fm BB et al., Phys. Rev. C 79, 034902 (2009) Mach cone for sound waves Diffusion wake

  20. Stopped Jet III BB et al., Phys. Rev. C 79, 034902 (2009) Normalized, background-subtracted isochronous Cooper-Frye at mid-rapidity pT = 5 GeV Energy Flow Distribution Assuming: Particles in subvolume will be emitted into the same direction Diffusion wake causes peak in jet direction Any conclusions about deposition mechanism???

  21. The Expanding Medium

  22. Expanding Medium I Experimental results based on many events b=0 Consider different jet paths A. K. Chaudhuri, Phys. Rev. C 75, 057902 (2007) , A. K. Chaudhuri, Phys. Rev. C 77, 027901 (2008) • Apply Glauber initial conditions and an ideal Gas EoS for massless gluons • Focus on radial flow contribution dE/dt = 1 GeV/fm Etot = 5 GeV • Two-particle correlation • (Tfreeze-out < Tcrit = 130 MeV): near-side jet Jet 150

  23. Expanding Medium II BB et al., Phys. Rev. Lett. 105, 222301 (2010) Etot = 5 GeV pTtrig= 3.5 GeV broad away-side peak double peaked structure due to non-central jets vjet =0.999 PHENIX, Phys. Rev. C 77, 011901 (2008)

  24. Expanding Medium III Etot = 10 GeV BB, arXiv:1012.4418 [nucl-th] pTtrig= 7.5 GeV broad away-side peak double peaked structure Strong impact of the Diffusion wake 6 < pTtrigger < 10 1.5 < pTassoc < 2.5 Causes smaller dip for pT=2 GeV Yield STAR, Phys. Rev. C 82, 024912 (2010) Path length dependence Centrality dependence f

  25. Expanding Medium IV Considering a bottomquark (M=4.5 GeV), propagatingatvjet < cs (energy-momentumdepositionscenario) pTassoc= 2.0 GeV PHENIX, PRL98, 232302 (2007) BB et al., Phys. Rev. Lett. 105, 222301 (2010) Conical emission angle also appears for subsonic jets Not a Mach cone Cu+Cu: Similaraway-sideshoulderwidth, double-peakstructurereapparsforpTassoc = 3 GeV

  26. Some more caveats

  27. Hot Spots I Can fluctuating initial condition explain the 2+3-particle correlations? Takahashi et al, PRL 103, 242301 (2009) R. Andrade et al., J. Phys. G 37, 094043 (2010) F. Grassi, Talk at the Glasma Workshop, BNL, May 2010

  28. Hot Spots II Check withonesinglehotspot Au, De/e0 = 2

  29. Hot Spots III Can hotspotsexplaineverything? pTassoc= 2.0 GeV pTtrig= 8.0 GeV pTtrig= 3.5 GeV BB, arXiv:1012.4418 [nucl-th] Bothleadto double-peakstructure Coalescedpeakonlyforjetevents Thereis a superpositionofjetsandfluctuatinginitialconditions Heavy quarkjetsneedtobestudied

  30. Heavy-flavorresults e-h correlationsfrom heavy-flavor decayshow a double-peakstructure on theaway-side Clear indicationthatthesignalis not just backgroundfluctuation A. Adare et al. [PHENIX], arXiv: 1011.1477[nucl-ex]

  31. Why v3 deformations cannot be the whole story • Correlation in Df1-Df2 • Df1/2 120° • No correlation in Dh1-Dh2 What are the consequences of triangular flow? B. Alver et al., Phys. Rev. C 81, 054905 (2010) B. Alver, Talk at the Glasma Workshop, BNL, May 2010 120° ptrigT=3 – 4 GeV, passocT=1 – 2 GeV J. Ulery [STAR], Int. J. Mod. Phys. E 16, 2005 (2007) ~ 120 v3couldbe due toinitialconditions (hotspots) OR due to a jettraversingthe medium The lattercaseshouldnotbesubtracted! Shock front??

  32. Fluctuating Initial Conditions

  33. Initial Conditions • Studying heavy-ioncollisionsrequiresa goodunderstandingoftheroleoftheinitialconditions: Glauber • Glauber model: incoherent superposition of p+p collisions • Color Glass Condensate (CGC): saturation effects are included B. Alver, Talk at the Glasma Workshop, BNL, May 2010 CGC • Theydiffer: • initial temperature gradients • initial high-pT parton distribution • distance travelled by each parton Leads to a different opacityestimate L. McLerran, Talk at a the CP Violation Workshop, BNL, April 2010

  34. Opacityofthe Medium • Exploringthepropertiesofthestrongly-coupledsQGP jet quenching: signal for creation of opaque matter (QGP) defined via: • Currentdescriptioncommonlybased on pQCDthough medium issupposedlysQGP D. D’Enterria, Lect. Notes Phys.785 (2010), 285 S. Bass et. al., PRC 79 (2009), 024901

  35. Caveat • pQCDdescriptionsdisagree in theirpredictionoftheazimuthalanisotropyofhigh-pThadrons, characterizing due tov2=v2(l) v2 is sensitive tothepathlength dependenceofenergyloss, scalingasdE/dx~ lz: S. Bass et. al., PRC 79 (2009), 024901 z=1 : pQCD z=2 : AdS/CFT (on-shell partons) z>2 : AdS/CFT (off-shellpartons) M. Gyulassy et. al., PRL 85 (2000), 5535 S. Gubser et. al., JHEP 0810 (2008), 052;P. Chesler et.al., PRD 79 (2009) 125015

  36. Energy-Loss Mechanisms • First investigationofv2(Npart) and RAA(Npart) for pT> 5 GeV hadrons is based on J. Jia et. al., PRC 82 (2010), 024902 pQCD-like AdS/CFT-like simple jetabsorption model • OnceRAA(Npart=350) ~ 0.18 for 0-5% p0 data • pQCD-like energy loss fails to reproduce v2(Npart) • AdS/CFT-like energy loss describes data for CGC initial conditions A. Adare et al, Phys. Rev. Lett. 105, 142301 (2010)

  37. Generic Energy Loss Model

  38. Generic Energy Loss Model Choosing an ansatz for the energy loss P: momentum of the jet(s) a,z: parameters controlling the jet-energy and path-length dependence k: being fixed thus that RAA(Npart=350) ~ 0.18 for most central data and considering Bjorken expansion via t0 = 2fm, one can determine the RAA(Npart), vn(Npart) Glauber:B.Betz et.al., arXiv:1102.5416 [nucl-th] CGC/KLN: H. Drescher et. al., PRC 76 (2007) 024905

  39. RAA and v2 a=0.3 z=1 z=2 • Having fixed k for • RAA(Npart=350) ~ 0.18 • RAA(Npart) can be • reproduced • z=1: v2 not reproduced • z=2: v2 reproduced for CGC initial cond. Small fluctuations for RAA(Npart) large fluctuations for v2(Npart) Notstraightforward todistinguishbetweeninitialconditions B.Betzet.al., arXiv:1102.5416 [nucl-th]

  40. RAA vs. IAA, and vn vs. vnIAA • Extend to dijet analysis, but considering kaway = k In contrast to Jia’s model, we fit the RAA vs. IAA J. Jiaet.al., arXiv:1101.0290 [nucl-th] • vn vs. vnIAA: • clear shift between Glauber and CGC model • saturation effect for larger z • It is necessary to alwaysdetermine the mean andthe with of a correlation! B.Betzet.al., arXiv:1102.5416 [nucl-th]

  41. Higher Harmonics z=1 z=2 • v3≠0 event-by-event, • v4 similar for average and event-by-event initial conditions Not suitable to distinguish between Glauber and CGC initial conditions B.Betzet.al., arXiv:1102.5416 [nucl-th] Higher harmonicsaremore sensitive tolocalgradients, but also toevent- by-eventfluctuations larger v3,4fluctuations

  42. Path-length dependence • Study the path-length dependence at b=8fm: • Once RAA is fixed via k, • sensitivity remains mostly for v2 and v3 saturationeffect occursfor larger z described by AdS/CFT off-shell partons S. Gubser et. al., JHEP 0810 (2008), 052;P. Chesler et.al., PRD 79 (2009) 125015 B.Betzet.al., arXiv:1102.5416 [nucl-th] • Measurement of virtuality in jet-photon collisions & v2,3 could lead to signature of AdS/CFT dynamics & microscopic mechanism of energy loss.

  43. Summary byaveragingoverdeflectedwakescreatedbyjets. • „Conical“ signal can be created (general effect): evenforsubsonicjets StructurecannotdirectlyberelatedtoEoS, but is a measurefortheflow • „Conical“ correlationscouldarisefrom multiple non-Mach sources Necessarytostudy heavy-flavortaggedjets. • Investigatedhigher Fourier harmonicsofjetquenching Showingthattheyareremarkablyinsensitivetothe Glauber andKLN/CGC model initialconditions • Studiedthepath-lengthdependencefor larger exponents a saturationeffectoccursfor larger exponents favoring an AdS/CFT energyloss

  44. Backup

  45. Jet - Studies in HIC Investigation of path length dependence: Double-peaked structure becomes more pronounced out-of-plane Could be due to deflection A. Sickeles [PHENIX], Eur. Phys. J. C 61, 583 (2009)

  46. Jet - Studies in HIC Centrality dependence: double-peaked structure for central collisions one peak structure for very peripheral collisions PHENIX, Phys. Rev. Lett. 97, 052301 (2006) Energy Scan: double-peaked structure occurs at about the same angle for different collision energies Mach cone??? J. Jia, Eur. Phys. J. C 62, 255 (2009)

  47. Stopped Jet • Jet stops after t=4.5/v fm BB et al., Phys. Rev. C 79, 034902 (2009) tFO=4.5/v fm tFO=6.5/v fm tFO=8.5/v fm Diffusion wake still present Vorticity conservation

  48. Stopped Jet Larger impact of thermal smearing Diffusion wake causes peak in jet direction BB et al., Phys. Rev. C 79, 034902 (2009) tFO=4.5/v fm tFO=6.5/v fm tFO=8.5/v fm

  49. Punch – Through Jet • Transverse momentum deposition: t=4.5/v fm BB et al., Phys. Rev. C 79, 034902 (2009) Still influence of diffusion wake from explosion of matter Vorticity conservation

  50. Mach Cones in Transport BAMPS: Boltzmann Approach of MultiParton Scatterings A transport algorithm solving the Boltzmann equations for on-shell partons with pQCD interactions Box scenario, no expansion, massless Boltzmann gas interactions, 2 -> 2 C. Greiner, Talk at the Opening Symposium of the JET Collaboration, Berkeley, June 2010 • The shock front (Mach front) gets broader and vanish with more dissipation

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