1. Precision Probes for Hot QCD Matter Rainer Fries Texas A&M University & RIKEN BNL QCD Workshop, Washington DC December 15, 2006

2. QCD DC 20062 Rainer Fries Precision Probes Overwhelming evidence for a new high-T state of nuclear matter at RHIC: (s)QGP  Different from normal nuclear matter  Probably no weakly interacting gas What are the properties of this new state?  Equation of state, transport properties, phase transitions Precision probes:  Rare (external) probes interacting with the plasma  Sufficient control of initial condition I Hard QCD probes & electromagnetic probes Theory:  Calculate framework (including initial state I )  Model jet-medium interaction Tests Suggest Scientists Have Found Big Bang Goo RHIC Scientists Serve Up “Perfect” Liquid New state of matter more remarkable than predicted -- raising many new questions BNL Press Release I F

3. QCD DC 20063 Rainer Fries Jets QCD jets as probes: controlled by pQCD. Paradigm: jet quenching through radiative energy loss (BDMPS, GLV, AMY, SW etc.)  Success: jet quenching prediction confirmed!  Transport coefficient Challenges for models:  Inclusive quantities: not very sensitive to  v 2 for jets? Path dependence?  Heavy quark energy loss?  Quark vs gluon energy loss?  Response of the medium? Theory framework in most cases:  Leading order pQCD + your favorite fireball model

4. QCD DC 20064 Rainer Fries PHENIX preliminary New Developments The age of tomography? Not yet, but … New ways to think about energy loss:  Collisional? Non-perturbative?  New data: ridge, cone, …  Collective medium response? Which modes?  What is jet, what is medium? Thermalization? Casalderrey-Solana QM06 Medium away near deflected jets away near Medium mach cone  13  12 1 2  12  13 The Cone The Ridge 3-particle correlations STAR preliminary STAR pp AuAu

5. QCD DC 20065 Rainer Fries E&M Probes Penetrating probes: photons + dileptons carry information from deep inside the fireball and/or early times  Access temperature via thermal emission and jet-photon conversion  Not yet well constrained Need new observables  Correlations  v 2 : jet-medium photons negative  Not observed (?) No radiative energy loss? Frantz QM06 PHENIX preliminary

6. QCD DC 20066 Rainer Fries The Future Go less and less inclusive to gain sensitivity  More correlations: h-h,  -h,  -jet  Gold-plated channel:  -h (Wang et al)  Very important to disentangle photon sources! Build more precise theory framework for hard probes initial conditions  Perturbative calculations at NLO  Couple calculations to hydro  Systematic analysis of final state effects without too much theory bias New ideas, improved models for jet-medium interactions. 0-10% 50-60% PHENIX preliminary In Plane Out of Plane LL Lajoie QM06

7. QCD DC 20067 Rainer Fries Questions For The Next Few Years What is the nature of parton energy loss? How strong are the different sources of photons and dileptons? Constrain the temperature and time evolution of the fireball test for hydrodynamics. How does the QCD medium react to jet energy loss? Dissipative? Collective? Are there Mach cone effects? Can we learn about the speed of sound, the equation of state? What are the transport properties of the quark gluon phase? How far up in momentum are (non-perturbative) recombination effects important?

8. QCD DC 20068 Rainer Fries Backup

9. QCD DC 20069 Rainer Fries Challenges Quark vs gluon energy loss: Heavy quarks:  Here: electrons from charm and bottom PHENIX

10. QCD DC 200610 Rainer Fries Elliptic Flow v 2 Finite impact parameter b > 0:  Spatial anisotropy in the initial state  Momentum anisotropy in the final state Space  momentum space translation x y z Test EOS of the system Test density/opacity of the medium Bulk/soft particles Hard particles + Photons

11. QCD DC 200611 Rainer Fries Length and energy scales Coherence length Transverse momentum accumulated through multiple scattering within the coherent regime  assume random walk   average momentum transfer set by the medium Define energy scale  LPM: Landau, Pomeranchuk, Migdal

12. QCD DC 200612 Rainer Fries Radiated Energy, : Incoherent regime, : LPM regime, : Coherent regime  LPM suppression factor

13. QCD DC 200613 Rainer Fries LPM Effect Energy loss: integrate radiation spectrum For E >  L :  LPM effect; quadratic dependence on the medium  Additional medium independent contribution For E <  L : Baier, Dokshitzer, Mueller, Peigne, Schiff, Zakharov

14. QCD DC 200614 Rainer Fries The Ridge Majumdar, Muller, Bass Wiedemann et al