1. Report on National Task Force On High Energy Density Physics NP members: Barbara Jacak Bill Zajc Tim Hallman (May 2004 workshop)

2. Charge & Context l At request of Interagency Working Group* on the Physics of the Universe chartered under the National Science and Technology Council. Charge letter from Joe Dehmer, NSF. l Goal: develop plans and set priorities in scientific areas that cut across agency lines within the federal government l High Energy Density Physics is “an area of significant promise” and is first area in which the agencies are charged to “develop a science-driven roadmap that lays out the components of a national program”. l Chair: Ron Davidson, Princeton Plasma Physics Lab Vice chair: Tom Katsouleas, USC * NSF, DOE, NASA, NRL, NIST, OSTP

3. Task Force Asked to l Identify principal areas of research that define the field of high energy density physics l For each area, identify the primary scientific questions driving the research l Develop scientific objectives and milestones in each area l Identify priorities for near term, including scientific opportunities and funding needs. Identify steps needed to establish priorities for the longer term l For each area, identify frontier facilities and infrastructure required for progress l Discuss the need for interagency coordination

4. Materials we drew on l Connecting Quarks with the Cosmos: Eleven Science Questions for the New Century l Frontiers in High Energy Density Physics – The X- Games of Contemporary Science l Science and Applications of Ultrafast, Ultraintense Lasers: Opportunities in Science and Technology Using the Brightest Light Known to Man (SAUUL workshop report, June 2002) And l Nuclear Science Long Range Plan

5. What is high energy density physics? In pictures: Map of The HED Universe ‘high energy density’:  > 10 11 J/m 3 P > 1 Mbar I > 3 X 10 15 W/cm 2 Fields > 500 Tesla

6. In words: Thrust Areas l HEDP in Astrophysical Systems l Beam-Induced HEDP RHIC produces the highest energy density of all, and fits into this category l HEDP in Stockpile Stewardship Facilities (Omega, Z-pinch, NIF, etc.) l Ultrafast, Ultra-intense Laser Science Common goal: strongly-coupled, many-body charged particle systems warm, dense matter with energy density ~ 10 11 J/m 3 astrophysical systems (e.g., brown dwarfs, and giant planets) intense ion, electron, photon beams can create these conditions strong interaction also produces strongly-coupled systems!

7. How does it fit together? l intellectually unifies physical regimes separated by orders-of-magnitude in density - temperature & research communities separated by traditional discipline boundaries. l These four areas reflect the fusing of four different physics communities (and funding bases) into an integrated scientific enterprise. l Such a fusing of research capabilities and intellectual interests provides many new opportunities for scientific discovery identified in this report. l Cross-fertilization of the plasma physics and nuclear physics communities may also lead to new ideas for how to diagnose the fundamental properties of quark- gluon plasmas, and even what questions to ask. From the report

8. HEDP in Astrophysics l Astrophysical Phenomena e.g. how do neutron stars, gamma ray bursters, etc.work? what is the universe made of? l Fundamental Physics properties of matter, interactions with energy under extreme conditions l Laboratory Astrophysics test astrophysical models and fundamental physics in the laboratory

9. Beam–Induced High Energy Density Physics l Heavy-Ion-Driven High Energy Density Physics and Fusion Accelerator and target developments l High Energy Density with Ultra-relativistic Electron Beams l Characterization of Quark-Gluon Plasmas

10. High Energy Density Physics in Stockpile Stewardship Facilities l Materials Properties l Compressible Dynamics l Radiative Hydrodynamics l Inertial Confinement Fusion

11. Ultrafast Ultraintense Laser Science l Laser Excitation of Matter at the Relativistic Extreme l Attosecond Physics l Ultrafast, High-Peak-Power X-Rays l Compact High Energy Particle Acceleration l Inertial Fusion Energy Fast Ignition

12. Nuclear Physics Compelling Questions l What is the nature of matter at the exceedingly high density and temperature characteristic of the Early Universe? l Does the quark gluon plasma exhibit any of the properties of a classical plasma?

13. Addressing these with heavy ion collisions l Create high(est) energy density matter similar to that existing ~1  sec after the Big Bang can study only in the lab – relics from Big Bang inaccessible T ~ 200-400 MeV (~ 2-4 x 10 12 K)  ~ 5-15 GeV/fm 3 (~ 10 30 J/cm 2 ) R ~ 10 fm, t life ~ 10 fm/c (~3 x 10 -23 sec) l Characterize the hot, dense medium expect QCD phase transition to quark gluon plasma does medium behave as a plasma? coupling weak or strong? What’s the density, temperature, radiation rate, collision frequency, conductivity, opacity, Debye screening length? probes: passive (radiation) and those created in the collision

14. Plasma coupling parameter? l High gluon density estimate  = / using QCD coupling strength =g 2 /d d ~1/(4 1/3 T) ~ 3T g 2 ~ 4-6 (value runs with T)  ~ g 2 (4 1/3 T) / 3T so plasma parameter  l So the quark gluon plasma is a strongly coupled plasma As in warm, dense plasma at lower (but still high) T But strong interaction rather than electromagnetic

15. What’s currently known? l Pressure built up very rapidly during ion collisions at RHIC observed collective flow viscosity small (known from hydro) interaction  large l Significant energy loss of fast quarks traversing medium energy & gluon density is large medium is opaque l Quasiparticles probably exist above Tc may experience binding, but not as normal hadron not color neutral as at T<Tc. Kolb, et al lQCD: Asakawa, Hatsuda

16. Current knowledge on properties l Extract from models, constrain by data Energy loss (GeV/fm)7-100.5 in cold matter Energy density (GeV/fm 3 )14-20>5.5 from E T data dN(gluon)/dy~1000From energy loss + hydro T (MeV)380- 400 Experimentally unknown as yet Equilibration time  0 (fm/c) 0.6From hydro initial condition; cascade agrees Opacity (L/mean free path)3.5Based on energy loss theory Equation of state? Early degrees of freedom? Deconfinement? Cross section of resonances at high T? Conductivity?

17. sensitivity to rare probes and improved background rejection for plasma radiation QGP is NOT rare in these collisions, but signals of early-time phenomena ARE! High p T hadrons, γ + jet, di-jets probe density, gluon bremstrahlung Heavy quarks (bound & unbound) probe screening, thermalization Direct photons, electrons radiation from plasma A+A Species scan p+p Energy scan p+A C,B Characterizing the quark gluon plasma

18. l High momentum or heavy quark probes High E(production)/short wavelength probes Screening properties via (c-anticharm) bound states Do the heavy quarks thermalize? Lose energy? higher luminosity  sufficient statistics of rare, or high pT quarks lattice QCD calculation under relevant conditions l Initial quark gluon plasma temperature Radiated photons, e+e- detector upgrades for background rejection lattice, hydro simulations (with relevant , coupling) l Characterize this new kind of plasma Radiation rate, conductivity, collision frequency, equation of state need rare probes, including tagged jets detector & luminosity improvements; simulations l Consistent theoretical picture of quark gluon plasma, heavy ion collision to connect with data need large scale computational resources for numerical simulation Scientific objectives for RHIC II:

19. How to get there? RHIC II l Experimental side – upgrade facility (~2009-2015) increase RHIC luminosity by ~40 by electron cooling of heavy ion beams l Capabilities of large detectors (2 steps between now & 2015) technology for rare features in high multiplicity events secondary decay vertices background rejection triggering, readout capabilities data analysis infrastructure (already write 0.5 pB/year) l Theory progress (over next 5-10 years) Large scale computing resources lattice QCD, hydrodynamic & transport simulations Personnel to develop new approaches

20. Theoretical tools l Large scale computations of fundamental properties Solve QCD on the lattice High T & dynamical quarks: need large computers l Simulations Hydrodynamics (2D mostly, 3D developing) pressure, viscosity, energy gradients, equation of state Cascade, non-equilibrium transport models pre-equilibrium stage, thermalization approach parton cascade for early phase hadron cascade for final state interactions QCD inspired models Hadronization (when T falls below Tc) not understood; collective effects must survive it l Constrain with data to extract plasma properties

21. Interagency opportunities? l Currently DOE/NP & NSF cooperate in this area RHIC operated by DOE/NP l Collaboration by DOE & NSF support for the people experimental & computational infrastructure grid computing large scale simulation and data analysis computational resources (other agencies? NNSA?) l Facility developments of interest to HED community Electron cooling technology (state of the art!) HED physics with RHIC beam itself?

22. Outcomes of taskforce for NP l Quark Gluon Plasma physics identified as thrust area in High Energy Density physics l RHIC II identified in report as an essential facility l A very interesting intellectual connection has been made between physicists studying electromagnetic and strong interaction plasmas. Commonality of theory, experimental techniques, language, properties is there. l Planning an RBRC workshop this fall to bring the communities together.

23. 10 11 J/m 3 equivalents * Laser or blackbody radiator onto a solid target *

24. Taskforce members Ronald C. Davidson, Chair, Tom Katsouleas, Vice-Chair Jonathan Arons, Matthew Baring, Chris Deeney, Louis DiMauro, Todd Ditmire, Roger Falcone, David Hammer, Wendell Hill, Barbara Jacak, Chan Joshi, Frederick Lamb, Richard Lee, B. Grant Logan, Adrian Mellissinos,David Meyerhofer, Warren Mori, Margaret Murnane, Bruce Remington, Robert Rosner, Dieter Schneider, Isaac Silvera, James Stone, Bernard Wilde, William Zajc Ronald McKnight, Secretary

25. Color screening? Lattice predictions for heavy quarks 40-90% most central N coll =45 0-20% most central N coll =779 20-40% most central N coll =296 NB: need temperature too!

26. Quantum Chromo Dynamic phase transition Color charge of gluons  self interaction; theory is non-abelian curious properties at large distance: confinement of quarks in hadrons + +… At high temperature and density: Debye screening by produced color-charges expect transition to free gas of quarks and gluons

27. RHIC at Brookhaven National Laboratory RHIC collides p, Au ions: 200 GeV/nucleon in c.m. 10 times the energy previously available!

28. 4 complementary experiments STAR

29. Study simple  complex systems: p+p, “p”+A, A+A collisions p-p PRL 91 (2003) 241803 Good agreement with NLO pQCD is QCD the right theory at RHIC? Perturbative for high p transfer processes? pp collisions: it works! Have a handle on initial NN interactions by scattering of q, g inside N We also need: Parton distribution functions Fragmentation functions 00

30. pQCD in Au+Au? direct photons [ w/ the real  suppression] (  pQCD x N coll ) /  background Vogelsang/CTEQ6 [if there were no  suppression] (  pQCD x N coll ) / (  background x N coll ) Au+Au 200 GeV/A: 10% most central collisions [   ] measured / [   ] background =  measured /  background Preliminary At high p T, it also works!  TOT    p T (GeV/c)

31. Estimate energy density In quark gluon plasma: Energy density for “g” massless d.o.f 8 gluons, 2 spins; 2 quark flavors, anti-quarks, 2 spins, 3 colors 37 (!) Normal nuclear matter:  ~ 0.2 GeV/fm 3 ;  ~ 0.17 /fm 3 ~ 12 T 4 ~ 2.4 GeV/fm 3

32. Where are we? 10 39 10 45 10 10 12 QGP at RHIC? 10 51 10 57

33. Screening in the QGP Follow usual derivation of Debye screening Now put in QGP scales and assumptions: Hadrons with radii greater than ~ D will be dissolved Origin of J/  suppression QGP signature Strong interaction