1. 1 “New Directions” Berndt Müller, Jamie Nagle, Peter Steinberg 2005 RHIC PAC Meeting BNL, November 11-12, 2005

2. 2 Process 1. Boulder Workshop, March 2005 2. 1st RHIC II workshop, April 2005 3. 2nd RHIC II workshop, June 2005 4. Various e-mail chains (in rhicii-new-l archives): “s” in sQGP, phonons, quasiparticles

3. 3 What is the “s”QGP Long email discussion on the “s”QGP – what the meaning of “s” is:  No consensus reached. “s” could mean: Strongly interacting/interactive Strongly coupled Large s-wave scattering Strange (in the sense of strangeness) Strikingly different  Independent of the semantics, there was no agreement on whether any of these terms had any meaning in a strict scientific sense.  Some argued that the “s”QGP was basically an effective slogan to get the scientific discussion, which had gotten stuck after QM2004, moving again, and should not be thought of a having a “hard” meaning.  The representatives of the lattice community argued vociferously that they have been telling us all along that the QGP above, but near Tc is not a state whose properties can be described by perturbation theory. They’re right!  But what is it ?! This is a scientific question of the first rank, up there – in my view – with the question what the dynamics of the Higgs field is.

4. 4 Correlations & quasiparticles Long discussions about correlation lengths and quasiparticle excitations:  Difference between equal-time correlation lengths (screening lengths etc.) and dynamical correlations related to the excitation and propagation of quasiparticles.  A liquid is characterized by the absence of “good” (meaning: long-lived) quasiparticles, with the notable exception of longitudinal phonons (sound). For benefit and amusement, read the archived messages at:  http://lists.bnl.gov/pipermail/rhicii-new-l/ http://lists.bnl.gov/pipermail/rhicii-new-l/ New Directions Working Group home page has moved:  http://www4.rcf.bnl.gov/~steinber/nd/

5. 5 The future is not what it used to be. Yogi Berra The future is here! Anonymous Back to the future. Robert Zemeckis When is a new direction “new”? Philosophical Background

6. 6 Conclusions We did not identify essential physics issues, which are radically new and have been overlooked so far. We identified essential physics issues for RHIC that need to be addressed in a more rigorous and (sorry!) systematic manner. These require a more careful delineation of the central questions and … A better coordinated interaction between theory and experiment. Some of these issues are not “new”, but they have become crisply visible through the RHIC data. Others were not even on the horizon before the start of the RHIC physics program.

7. 7 1. Deconfinement and chiral symmetry restoration What is the physics of the QCD phase transformation? 2. Entropy Generation How and why does it thermalize so fast? 3. State of Matter What really is an ideal relativistic quantum fluid? 4. Degrees of freedom Is it a (s)QGP or something else? 5. Phase Transitions Is there a critical point and can RHIC see it? Fundamental Physics Questions

8. 8 QCD: Lagrangian tells us that “free” quarks and gluons are the fundamental degrees of freedom in nature pQCD: Factorization theorems suggest that we can abstract away the “soft” physics in the limit of large Q 2 High-  QCD: At high temperatures, there is a change in the structure of strongly interacting matter The Faces of QCD

9. 9 Paths to Progress RHIC (I) was built to explore “new directions” in the physics of strongly interacting matter. It has done so, and in so doing, it has opened up new “new directions”, which were not seen before the RHIC physics program started. These are the “new directions” to be studied in the evolving RHIC physics program. They provide the science case for RHIC II. There remains a lot to be done to map out the old “new directions” on which the original RHIC physics program was based. There is also the need to explore physics in the energy regime beyond RHIC. But none of the questions discussed here require higher beam energy to be studied. RHIC I RHIC II DOE

10. 10 What Does It Take? Good science needs cleanly formulated ideas and questions Good science proceeds step by step Progress consists not only in asking “new” questions, but also in sharpening and refining “old” ones Promising approaches to RHIC II physics:  Upgrade experiments and accelerator  More adequate support for systematic development of theoretical concepts, tools, and phenomenology Warning: FY06 budget CUTS are a disaster ready to hit us. Many RHIC theory efforts will be devastated!  Intense brainstorming discussions (“Boulder Workshops 2  N”) with concrete follow-up (provide motivation for doing follow-up work?)