1
New Directions

• Berndt Müller, Jamie Nagle, Peter Steinberg
• 2005 RHIC PAC Meeting
• BNL, November 11-12, 2005

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
What is the sQGP

• Long email discussion on the sQGP 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 sQGP 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. Theyre 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
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/
• New Directions Working Group home page has moved
• http//www4.rcf.bnl.gov/steinber/nd/

5
Philosophical Background
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?
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
Fundamental Physics Questions

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

8
The Faces of QCD
QCDLagrangian tells us that free quarks and
gluons are the fundamental degrees of freedom in
nature
High-e QCDAt high temperatures, there is a
change in the structure of strongly interacting
matter
pQCDFactorization theoremssuggest that we can
abstract away the soft physics in thelimit of
large Q2
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.
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?)