1. Poking at the Quark Gluon Plasma with Jets and Heavy Quarks

2. Scattered partons propagate: fast quarks & gluons traverse the interesting stuff radiate gluons interact with QGP partons Fragment into jets -usually described by phenomenological fragmentation function -in/outside the medium What’s this stuff? let’s poke it with a stick! follow in the footsteps of Rutherford and friends experimenting with radioactivity…

3. lattice QCD F. Karsch properties of matter l thermodynamic (equilibrium) T, P,  EOS (relate T,P,V,  ) v sound, static screening length l transport properties* particle number, energy, momentum, charge diffusion sound viscosity conductivity * measuring these is new for nuclear/particle physics! ^ QCD

4. plasma l ionized gas which is macroscopically neutral exhibits collective effects l interactions among charges of multiple particles spreads charge out into characteristic (Debye) length, D multiple particles inside this length they screen each other plasma size > D l “normal” plasmas are electromagnetic (e + ions) quark-gluon plasma interacts via strong interaction color forces rather than EM exchanged particles: g instead of  gluons self-interacting, number (not fixed)  T

5. typical plasma diagnostics X-ray tomography: to get temporal and spatial evolution of plasma mode activity, use 10 soft X-ray cameras with 20 channels each, at 70 kHz max.

6. heavy ion collision diagnostics  K  p  n  d, Hadrons reflect (thermal) properties when inelastic collisions stop (chemical freeze-out). not possible to measure as a function of time nature integrates over the entire collision history thermal radiation ( ,  e + e -,  +   color-screened QGP  pressure builds up Hard scattered q,g (short wavelength) probes of plasma formed time

7. study plasma by radiated & “probe” particles l as a function of transverse momentum p T = p sin  with respect to beam direction) 90° is where the action is (max T,  ) p L midway between the two beams: midrapidity l p T < 1.5 GeV/c “thermal” particles radiated from bulk of the medium l p T > 3 GeV/c jets (hard scattered q or g) heavy quarks, direct photons describe by perturbative QCD produced early→“external” probe

8. RHIC at Brookhaven National Laboratory Collide Au + Au ions for maximum volume  s = 200 GeV/nucleon pair, p+p and d+A to compare STAR

9. Experimenter’s Tools STAR specialty: large acceptance measurement of hadrons PHENIX specialty: rare probes, leptons, and photons

10. a bit of geometry, terminology l baseline for heavy ion collisions: p+p collisions l peripheral collisions (large impact parameter) are like a handful of p+p collisions l central (small impact parameter) collisions produce largest plasma volume, temperature, lifetime l report centrality as fraction of total A+A cross section »0-5% = very central peripheral: few participant nucleons (small N part ) few NN collisions (N coll ) central: large N part & N coll Ncoll near 1000 in ~ head-on Au+Au

11. The matter is opaque! jets are quenched p-p PRL 91 (2003) 241803 Good agreement with pQCD head-on Au+Au N coll = 975  94 

12. colored objects lose energy, photons don’t how opaque is hot QCD matter?

13. interaction of radiated gluons with gluons in the plasma greatly enhances the amount of radiation energy loss by induced gluon radiation opacity expansion analysis shows / mean free path ~ 3.5 →  ~ 1400 gluons/unit rapidity I. Vitev d+Au Au+Au

14. energy transport

15. constrain with data extract transport parameter q from data, get ~ 13 GeV 2 /fm but pQCD favors ~1 (Baier, et al ) ^ PQM model: C. Loizides Eur.Phys.J. C49 (2007) 339 data & fit: arXiv:0801.1665

16. momentum exchange: complicated process The medium is dense and opaque! Quantifying energy deposit..ongoing Different models include radiation, w/ or w/o collisions some/no transfer medium→probe different level of detail describing collision geometry different handling of fluctuations different description of the expansion dynamics

17. medium transport of deposited energy? l study using hadron pairs l high p T trigger to tag hard scattering l second particle to probe the medium Central Au + Au opposing jet collective flow in underlying event same jet

18. at high momentum, jets punch through STAR central collisions on away side: same distribution of particles as in p+p but ~5 times fewer! expected for opaque medium X Phys.Rev.Lett. 97 (2006) 162301

19. 2/8/2008Quark Matter 2008 Direct Photon-Hadron  Correlations in p+p 2/8/2008Quark Matter 2008 19  [rad] 1/Ntrig dN/d  (A.U.) M.A. Nguyen toward jet tomography: Compton scattering q+g → q+   tags q energy 12-15 GeV “monoenergetic jet”  0 - h  dir - h  right mechanism  same jet partners are absent  away jet shows similar modification  next step: quantify energy/momentum flow

20. Where we need to go  tags q energy l >12 GeV “monoenergetic” jets l all we need is: more events bigger detector coverage l all those near-by curves very different with no medium ALL use weak coupling! RHIC II AuAu 20 nb -1  -jet

21. lower p T partners look funny! medium responds to the “lost” energy 3<p t,trigger <4 GeV p t,assoc. >2 GeV Au+Au 0-10% preliminary STAR 1 < p T,a < 2.5 < p T,t <4 GeV/c peripheralcentral

22. jets shock the medium p+p central Au+Au

23. lost energy excites a sound (density) wave? if shoulder is sound wave… LOCATION at  +/-1.23=1.91,4.37 → speed of sound cos  m =c s ~0.35-0.4 (c s 2 =0.33 in QGP,~0.19 in hadron gas) relative excitation of sound and diffusion wake in intense study data → sound mode large Gubser,Pufu,Yarom PRL100, 012301’08 Chesler & Yaffe, 0706.0368(hep-th) strong coupling: ask AdS/CFT answer: yes it does! mach cone wake

24. Diffusion of heavy quarks traversing QGP l How do they interact? l Prediction: lower energy loss than light quarks large quark mass reduces phase space for radiated gluons l Measure via semi-leptonic decays of mesons containing charm or bottom quarks D Au D X e±  K

25. c,b decays via single electron spectrum compare data to “cocktail” of hadronic decays

26. sufficient interaction to equilibrate?? l Measure correlation of e ± with the light hadrons l Ask whether they flow along. l NB: rate of equilibration gives information on the viscosity of the liquid! PRELIMINARY Run-4 Run-7 Rapp & van Hees, PRC 71, 034907 (2005) minimum-bias Heavy quarks do flow!! Use to probe transport properties of QGP!

27. heavy quarks lose energy too cannot be dominantly by bremsstrahlung (gluon radiation) plasmas have collisions among constituents! including it helps larger than expected scattering  → stronger coupling e± from heavy quark decay Wicks et al., NPA 784(2007)426

28. heavy quark transport: diffusion & viscosity l diffusion = brownian motion of particles definition: flux density of particles J = -D grad n l integrating over forward hemisphere: D = diffusivity = 1/3 so D = / 3n  D  collision time, determines relaxation time Langevin: equation of motion for diffusion thru a medium drag force  random force  /unit time  D* particle concentration = mean free path note: viscosity is ability to transport momentum  = 1/3  so D =  S → measure D get  ! * G. Moore and D. Teaney, hep-ph/0412346

29. confronting mechanisms with data PRL98, 172301 (2007) Radiative energy loss alone: fails to reproduce v 2 Heavy quark transport model (i.e. diffusion) shows better agreement with R AA and v 2 Though agreement with data is so-so, slow relaxation ruled out by v 2 D ~ 4-6/(2  T) for charm  /S = (1.3 – 2.0)/ 4 

30. S. Gavin and M. Abdel-Aziz: PRL 97:162302, 2006 p T fluctuations STAR Comparison with other estimates R. Lacey et al.: PRL 98:092301, 2007 v 2 PHENIX & STAR H.-J. Drescher et al.: arXiv:0704.3553 v 2 PHOBOS conjectured quantum limit estimates of  /s based on flow and fluctuation data indicate small value as well close to conjectured limit significantly below  /s of helium (  s ~ 9)

31. What about b quarks? PRL 98, 172301 (2007) e ± from heavy flavor b quark contribution to single electrons becomes significant. do they also lose energy?

32. Hard probes tell us: l Energy loss in the plasma is large. and/or  s ~ 0.27. What quantity DO we measure? Eloss mechanism? l Deposited energy shocks the medium. Mach cones? c s ~ (0.35 – 0.4) c (closer to hadron gas than QGP) expected diffusion wake AWOL (baryon enhancement?) l Medium is also opaque to charm quarks Heavy quark diffusion, hadron flow & fluctuations →viscosity:  S = (1 – 3)/ 4  close to conjectured bound l First hint of b decay contributions bottom quarks maybe not gobbled up by medium?

33. for further (experimental) progress STAR HFT PHENIX VTX Si vertex detectors separate c from b -3 -2 -1 0 1 2 3 rapidity NCC MPC VTX & FVTX  HBD EMCAL RHIC II AuAu 20 nb -1  -jet acceptance and ∫ L mechanism of eloss and do it again at higher T at the LHC!

34. l backup slides

35. long standing baryon puzzle… baryons enhanced for 1.5 < p T < 5 GeV/c coalescence of thermal quarks from an expanding quark gluon plasma. STAR

36. baryons come from jets – enhanced by wake? ● the “extra” baryons have jet-like partners ● only in central collisions do we see a dilution from thermal baryons meson-meson baryon- meson Near side ●collectively flowing medium boosts quarks to higher p T ● wake of fast quark builds particle density to coalesce ● baryon enhancement reflects dynamics…?! speculate: Gubser, Pufu, Yarom 0706.4307(hep-th)

37. sound wave (shoulder) vs. jet remnant shoulder (medium response) jet remnant away-side total pp collisions peripheral central

38. sum associated p T observed in charged particles punch-through decreases vs. p+p shoulder grows with centrality near & far totals both increase (line: expected in PHENIX acceptance according to PYTHIA generator) ratio near/far: nearly constant with centrality! at p+p value! near side increase tracks away side loss of  p T in punch-through balanced by shoulder growth

39. Ratio of Away p T asso / near p T asso l Ratio constant with centrality l Consistent with p+p value, also with PYTHIA l Even though the total vector sum of nearside/awayside both increase, the ratio of the two still hold constant, i. e. the total contribution from “head” and “shoulder” part is hold, but the portion between the two is changing. head shoulder Head+shoulder PYTHIA

40. LPM effect up to O (g s ) + (3+1)d hydro + collisions Qin, Ruppert, Gale, Jeon, Moore and Mustafa, 0710.0605 Fix initial state by constraining hydro with particle spectra Reproduce observed energy loss vs. centrality using  s = 0.27

41. Three particle correlations Two Analysis Approaches: Cumulant Method Unambiguous evidence for true three particle correlations. Two-component Jet+Flow-Modulated Background Model Within a model dependent analysis, evidence for conical emission in central Au+Au collisions p T trig =3-4 GeV/c p T assoc =1-2 GeV/c off-diagonal projection d+Au 0-12% Au+Au  =(  1  2 )/2 Δ2Δ2 Δ1Δ1 Δ1Δ1 0-12% Au+Au: jet v 2 =0 Δ2Δ2 From J. Dunlop, Montreal Workshop ‘07 C. Pruneau, QM2006 J. Ulery, HP2006 and poster, QM2006

42. more complex jet fragment measurements l 3 – particle correlations consistent with Mach-cone shoulder l sum of jet fragment momentum ▪ increases together on trigger and away sides ▪ momentum loss in punch-thru jet balanced by momentum in the shoulder peak ▪ evidence for wakes? d+Au 0-12% Au+Au Δ2Δ2 Δ1Δ1

43. suppression at RHIC very similar to that at SPS! why?? more suppressed at y  0 PHENIX PRL98 (2007) 232301 J/  screening length: onium spectroscopy 40% of J/  from  and  ’ decays they are screened but direct J/  not? Karsch, Kharzeev, Satz, hep-ph/0512239 y=0 y~1.7

44. what does non-perturbative QCD say? Lattice QCD shows heavy qq correlations at T > T c, also implying that interactions are not zero Big debate ongoing whether these are resonant states, or “merely” some interactions Color screening – yes! but not fully… Some J/  may emerge intact Hatsuda, et al. J/  is a mystery at the moment! Others may form in final state if c and cbar find each other

45. are J/  ’s regenerated late in the collision? c + c coalesce at freezeout → J/  R. Rapp et al.PRL 92, 212301 (2004) R. Thews et al, Eur. Phys. J C43, 97 (2005) Yan, Zhuang, Xu, PRL97, 232301 (2006) Bratkovskaya et al., PRC 69, 054903 (2004) A. Andronic et al., NPA789, 334 (2007) R. Rapp et al.PRL 92, 212301 (2004) R. Thews et al, Eur. Phys. J C43, 97 (2005) Yan, Zhuang, Xu, PRL97, 232301 (2006) Bratkovskaya et al., PRC 69, 054903 (2004) A. Andronic et al., NPA789, 334 (2007) should narrow rapidity dist. … does it? central peripheral J/  is a mystery at the moment!

46. plasma basics – Debye screening l distance over which the influence of an individual charged particle is felt by the other particles in the plasma charged particles arrange themselves so as to effectively shield any electrostatic fields within a distance of order D D =  0 kT ------- n e e 2 Debye sphere = sphere with radius D l number electrons inside Debye sphere is large N D = N/V D =  V D V D = 4/3  D 3 1/2 n e = number density e = charge

47. plasma frequency and oscillations l instantaneous disturbance of a plasma → collective motions plasma wants to restore the original charge neutrality electrons oscillate collectively around the (heavy) ions characterized by natural oscillation frequency plasma frequency it’s typically high l restoring force: ion-electron coulomb attraction l damping happens via collisions if e-ion collision frequency < electron plasma frequency  pe /2  then oscillations are only slightly damped a plasma condition: electron collision time large vs. oscillation n e e 2  p = ------ m e  0 1/2

48. For all distributions described by temperature T and (baryon) chemical potential   : dn ~ e -(E-  )/T d 3 p Does experiment indicate thermalization? T f ~ 175 MeV

49. minimum  at phase boundary? Csernai, Kapusta & McLerran PRL97, 152303 (2006) quark gluon plasma B. Liu and J. Goree, cond-mat/0502009 minimum observed in other strongly coupled systems – kinetic part of  decreases with  while potential part increases strongly coupled dusty plasma

51. Elliptic flow scales with number of quarks transverse KE implication: valence quarks, not hadrons, are relevant pressure field builds early → dressed quarks born of flowing field (as strongly interacting liquids lack well-defined, long-lived quasi-particles)

52. The acid test for quark scaling  meson (bound state of s+sbar) mass ~ m proton but flows like the mesons PHENIX

54. dielectron spectrum vs. hadronic cocktail

55. R.Rapp, Phys.Lett. B 473 (2000) R.Rapp, Phys.Rev.C 63 (2001) R.Rapp, nucl/th/0204003 low mass enhancement at 150 < m ee < 750 MeV 3.4±0.2(stat.) ±1.3(syst.)±0.7(model) Comparison with conventional theory calculations: min bias Au+Au they include: QGP thermal radiation chiral symmetry restoration

56. Direct photon v 2

57. transport in QGP (theoretical approach) weak coupling limit strong coupling limit perturbative QCD not so easy! kinetic theory, cascades gravity  supersym 4-d QCD-like theory resummation of hard thermal loops

58. Collectivity: measuring elliptic flow (v 2 ) dN/d  ~ 1 + 2 v 2 (p T ) cos (2  ) + … “elliptic flow” Almond shape overlap region in coordinate space x y z momentum space

59. v 2 is large & reproduced by hydrodynamics must begin hydro in < 1 fm/c viscosity must be ~ 0 - 0.1 i.e. “perfect” liquid viscosity decreases longitud. pdV work → higher transverse velocity First indication of small  /S data constrains hydro: as in plasma physics D. Teaney, PRC68, 034913 (2003)

61. Quark Matter – 5 February 2008Michael P. McCumber for PHENIX Away-side Composition arXiv:0712.3033 Shapes: - Similar shape in away-side mesons and baryons Ratios: - Away-side baryon/meson ratios approach inclusive values - Incompatible with in-vacuum fragmentation

62. Quark Matter – 5 February 2008Michael P. McCumber for PHENIX Connections - Centrality PHENIX poster (Chin-Hao Chen) - Away-side shoulder and near-side ridge share a common centrality dependence - Scale similarity here is largely a factor of p T selection

63. Quark Matter – 5 February 2008Michael P. McCumber for PHENIX Connections - Balance 0.0 < | Δη| < 0.1 0.5 < | Δη| < 0.7 - Jet & Ridge balances Shoulder & Head - Ridge & Shoulder balance seperately!