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Cooking Nuclear Matter

Cooking Nuclear Matter. A culinary pedestrian's tour through the world of QCD matter. Richard Seto. RHIC physicists (including me). “The emergence of QCD is a wonderful example of the evolution from farce to triumph” David Gross, from his Nobel Lecture. Intro QCD Some thermo Some Lattice

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Cooking Nuclear Matter

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  1. Cooking Nuclear Matter A culinary pedestrian's tour through the world of QCD matter Richard Seto RHIC physicists (including me) “The emergence of QCD is a wonderful example of the evolution from farce to triumph” David Gross, from his Nobel Lecture

  2. Intro QCD Some thermo Some Lattice Experimental stuff A. A first look Energy Density equilibration Temperature ->NDOF B. Characterizing the stuff we found Viscosity jet quenching Mach cones? Conclusions questions Implications A roadmap

  3. Quantum ChromoDynamics • QCD : established theory of the strong interaction • Elements – quarks (3 colors), gluons (8 color combinations) • quark confinement the non-perturbative structure of the vacuum  responsible for hadronic mass • vacuum structure • modified at high temperatures •  quarks and gluons deconfined at high ______temperatures QCD is a fundamental theory of nature containing a phase transition that is accessible to experimental investigation

  4. What happens when you cook the nucleus? From Fermi notes on Thermodynamics RHIC

  5. Preliminaries

  6. a first guess: Degrees of Freedom Can we melt the hadrons and liberate quark and gluon degrees of freedom? Energydensity for “g” massless d.o.f. (bosons) Hadronic Matter: quarks and gluons confined For T ~ 200 MeV, 3 pions with spin=0 Quark Gluon Matter: 8 gluons; 2(3) quark flavors, antiquarks, 2 spins, 3 colors 37 (48) !

  7. Predictions (Lattice QCD) • Lattice QCD • Static Properties of QCD matter • Reliable way to do calculations of tough (e.g. many body/strongly interacting) problems • Order Parameters • chiral condensate ~ chiral symmetry • polyakov (wilson) loop • analogy – spin (color) lattice • low temperature – spins (colors) correlated • quark anti-quark interaction confines • high temperature – spins (colors) uncorrelated due to thermal fluctuations • quark anti-quark interaction will no longer confine

  8. Lattice: TC~190 MeV (C ~ 1 GeV/fm3) Phase transition- fast cross over to experimentalist: 1st order The Critical temperature difference between S-B and lattice interactions (in hindsight)

  9. The experimental facility

  10. Why do it • we have NO IDEA what it is really like • Properties (dynamical – lattice can calculate static only) • viscosity • thermal conductivity • ??? • innovations in both experiments and theory • Strings • hydro models (3d viscous relativistic) • initial state – new non-perturbative QCD methods

  11. STAR BNL-RHIC Facility Soon to Come – the LHC Collide Au + Au ions for maximum volume s = 200 GeV/nucleon pair, p+p and d+A to compare

  12. What does an Au+Au Collisions at 200 GeV Center of mass look like?

  13. “Spectators” “Participants” “Spectators” Centrality ~ impact parameter Impact Parameter Centrality def’n 0%: head on 90%: glancing BinaryCollisions • Hard interactions ~ Ncollisions Use a Glauber model Participant

  14. transverse momentum pt time Stages of the Collision • Relativistic Heavy Ion Collisions • NOT a bottle of compressed quarks and gluons • Better analogy – early universe • Time evolution • Lorenz contracted pancakes • Pre-equilibrium < ~1fm/c ?? • QGP and hydrodynamic expansion ~ few fm/c ?? • Hadronization and freezout ~ 5-20 fm/c??

  15. the energy density – a simple calculation

  16. Bjorken Energy Density y=rapidity ~ Lorentz invariant velocity Bjorken imagined a cylinder of matter which was boost invariant We want only thermal energy, not remnants of beam momentum Two nuclei pass through one another leaving a region of produced particles between them.

  17. Energy Density Energy density far above transition value predicted by lattice. R~7fm pR2 2ct PHENIX: Central Au-Au yields

  18. II Flow and equilibrium

  19. py px z y x  Flow: A collective effect pressure Coordinate space: initial asymmetry Momentum space: final asymmetry • dn/d ~ 1 + 2v2(pT)cos (2 ) + ... • Initial spatial anisotropy converted into momentum anisotropy. • Efficiency of conversion depends on the properties of the medium.

  20. Strong flow Implies early thermalization • If system free streams • spatial anisotropy is lost • v2 is not developed (Teany et al, Huovinen et al)

  21. PHENIX Huovinen et al Strong flow Implies early thermalization • If system free streams • spatial anisotropy is lost • v2 is not developed • detailed hydro calculations (QGP+mixed+RG, zero viscosity) • 0 ~ 0.6 -1.0 fm/c • ~15-25GeV/fm3 • (ref: cold matter 0.16 GeV/fm3)

  22. III Temperature

  23. exp + Ncoll scaled pp Fit to pp NLO pQCD (W. Vogelsang) black body radiated photons Tinit Direct photon yield MB In p+p: pQCD works to low pT In Au+Au: soft (thermal) excess fit with exponential T = 221 ± 23 ± 18 MeV (central) T = 224 ± 16 ± 19 MeV (MB) less central central pp arXiv: 0804.4168

  24. time(fm/c) Tinit (MeV) Tinit > Tc ! To unfold hydro evolution: Compare to photon spectrum from hydro models D’Enterria & Peressounko, EPJ C46 (2006) 451 T decreasing with time Tinit ~ 300-600 MeV Tc ~ 190 MeV

  25. NDOF? a Sanity check hadron gas “QGP” choose τ0 ~0.5-0. 6 fm/c good…

  26. IV Viscosity Now open pot and probe what is inside? Can we get a hold of the dynamic properties?

  27. Hydrodynamics Hydrodynamic Equations Energy-momentum conservation Charge conservations (baryon, strangeness, etc…) Need equation of state(EoS) P(e,nB) For perfect fluids (neglecting viscosity!), Energy density Pressure 4-velocity Within ideal hydrodynamics, pressure gradient dP/dx is the driving force of collective flow.  Collective flow is believed to reflect information about EoS!  Phenomenon which connects 1st principle with experiment the viscosity is set to zero! – and the models work ???

  28. the Perfect Fluid? Viscous less Viscous

  29. Los Angles Times – May 2005 WHAT?! Flow, Hydrodynamics, Viscosity, Perfect Fluids…. ? YUK! and String Theory

  30. Fluids: Ask Feynman ( from Feynman Lecture Vol II) • The subject of the flow of fluids, and particularly of water, fascinates everybody….we watch streams, waterfalls, and whirlpools, and we are fascinated by this substance which seems almost alive relative to solids. …. • The subject of the flow of fluids, and particularly of water, fascinates everybody…. Surely you’re joking Mr. Feynman

  31. [ ] Viscosity and the equation of fluid flow =density of fluid =potential (e.g. gravitational-think mgh) v=velocity of fluid element p=pressure Sheer Viscocity Bernoulli

  32. [ ] Non-ZERO Viscosity smoke ring diffuses smoke ring dissipates

  33. [ ] ZERO Viscosity does not diffuse smoke ring keeps its shape Viscosity dissipates momentum note: you actually need viscosity to get the smoke ring started

  34. Anisotropic Flow • Conversion of spatial anisotropy to momentum anisotropy depends on viscosity • Same phenomena observed in gases of strongly interacting atoms (Li6) M. Gehm, et alScience 298 2179 (2002) strongly coupled viscosity=0 weakly coupled finite viscosity The RHIC fluid behaves like this, that is, viscocity~0

  35. Can we anyone calculate the viscosity?A primer on viscosity (Feynman again) the low-brow sheer force(stress) is: energy momentum stress tensor

  36. Using Maldecena 10-D string theory magici.e. AdS/CFT duality Gravity “QCD” “QCD” strong coupling N=4 supersymmetry ~ almost QCD “SYM” (OK the coupling constant doesn’t run, but I am interested in the strong coupling case, there are a bunch of extra particles so we will divide by the entropy to get rid of the extra DOF…) Gravity dual Policastro, Son, Starinets hep-th 0104066 “The key observation… is that the right hand side of the Kubo formula is known to be proportional to the classical absorption cross section of gravitons by black three-branes.” σ(0)=area of horizon

  37. finishing it up Entropy black hole “branes” Entropy “QCD”  Area of black hole horizon Entropy black hole Bekenstetein, Hawking = =σ(0) k=8.6E -5 eV/K Kovtun, Son, Starinets hep-th 0405231

  38. viscocity~0, i.e. A Perfect Fluid? viscosity bound? nitrogen helium water • See “A Viscosity Bound Conjecture”, P. Kovtun, D.T. Son, A.O. Starinets, hep-th/0405231 • THE SHEAR VISCOSITY OF STRONGLY COUPLED N=4 SUPERSYMMETRIC YANG-MILLS PLASMA., G. Policastro, D.T. Son , A.O. Starinets, Phys.Rev.Lett.87:081601,2001 hep-th/0104066 lowest viscosity possible?

  39. A new way of thinking??? “QCD” strong coupling Gravity dual 4d boundary z 5d bulk theory z: analogy imaginary axis, analytic continuation Possibility to solve a strongly coupled theory! (for the first time??)

  40. V. Jet quenching Deep inelastic scattering

  41. The experiment we would like to do – Deep Inelastic Scattering of the QGP “hard” probes Formed in initial collision with high Q2 penetrate hot and dense matter sensitive to state of hot and dense matter dE/dx by strong interaction  jet quenching Hard Probes In Heavy Ion Collisions, aka Jet quenching Beams of colored quarks Colorless Hadrons Colored QGP hadronic phase and freeze-out QGP and hydrodynamic expansion Hard parton Softened Jet pre-equilibrium hadronization

  42. Ncoll Scaling • Particle production via hard processes should scale with Ncoll, the number of underlying binary nucleon-nucleon collisions • Assuming no “suppression effects”

  43. peripheral Au+Au 10 5 pT (GeV/c) Parton Energy Loss – π0 Production • Calibrating the probes- pp reference data -agrees with NLO pQCD • Peripheral Collisions -Scale with Ncoll • Central Collisions DO NOT SCALE! Central 0-10% PHENIX

  44. What is the energy density? “Jet quenching” AuAu 200 GeV direct photons scale as Ncoll p0suppressed by 5! Direct γ • Calculations: • dNg/dy ~ 1000 • Wicks et al, nucl-th/0512076 •  ~10-15 GeV/fm3 • critial ~0.6 GeV/fm3 0.2 π0 η RAA

  45. Can you look at Di-jets?

  46. Jet correlations in proton-proton reactions. Strong back-to-back peaks. Jet correlations in central Gold-Gold. Away side jet disappears for particles pT > 2 GeV Jet correlations in central Gold-Gold. Away side jet reappears for particles pT>200 MeV Leading hadrons Medium Jet on the “other” side? Azimuthal Angular Correlations

  47. Almost complete extinction of jetIs this remarkable? • An email from me to Ray Orbach (head of DOE office of science) after rumors that funding might be in trouble (Aug 2002) • As you might know, the most interesting observation made at RHIC is that of the suppression of high-pt hadrons, which may me an indication of jet quenching. This is a remarkable effect. It is as if a bullet fired from a 22 rifle were stopped by a piece of tissue paper (actually by weight, the tissue paper would stop a bullet with 1000x the kinetic energy of an ordinary 22 bullet. Is this interesting? Just as a physical phenomena, it certainly seems to me to be quite extraordinary. The stuff that is being created - presumably a QGP is about the most viscous stuff on earth. right dead wrong

  48. mu~3 MeV md~5 MeV ms~100 MeV mc~1,300 MeV mb~4,700 MeV ΛQCD~200 MeV heavy quark suppression? boulder throw a pebble in the stream see if it moves Pooh and Rabbit playing pooh sticks

  49. Centrality Dependence of RAA Non photonic electrons (aka charm+bottom) PRL 98, 172301 (2007) • updated result on flow of non-photonic e± • saturation at pT ~ 2.5 GeV charm suppressed and thermalizes What fraction of this is bottom? • high pT non-photonic e± suppression increases with centrality • similar to light hadron suppression at high pT • careful: decay kinematics!

  50. Answer: measure B/B+C in pp bottom is a substantial (~50%) fraction of non-photonic electrons and dominates after 5 GeV bottom is suppressed bottom flows and is thermalized

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