Program Advisory Committee (PAC)
All Staff MemoCall for Requests for Presentations to the PAC23 Review
of the Science Driving the 12 GeV Upgrade
October 14, 2002
I am writing to bring to your attention a special session of the JLab Program Advisory Committee that will be held in conjunction with the meeting of PAC23 to review our plans for the science and the experimental equipment of the 12 GeV Upgrade project. This review will be undertaken in the same spirit as the special session of PAC18 that reviewed an earlier version of those plans as we prepared the White Paper presented to the 2001 NSAC Long Range Plan. In particular, in preparation for the final editing of the pre-Conceptual Design Report (pCDR) for the upgrade, PAC23 will review the science motivation developed for the White Paper and consider proposals for modifications of and additions to that science motivation. If you or a group you represent are interested in proposing such a modification or addition, please read this document carefully for details of how the PAC review will take place. The PAC will also take a first look at the success we have had in "orthogonalizing" the experimental equipment planned for the four halls.
As you know, much progress has been made over the past year toward a Conceptual Design Report for the 12 GeV Upgrade. Draft preliminary Conceptual Design Reports (pCDRs) have been produced by interested scientists in each of the present halls and by the collaboration proposing the new GlueX ("Hall D") experiment. The Accelerator Division has developed a revised draft of the pCDR for the accelerator upgrade. Over the next few months we must merge these documents into a final pCDR for the entire project. The pCDR will serve as the definition of our aspirations and plans until the project is formally underway, and R&D begins in preparation for the development of the final Conceptual Design Report (CDR) on which the construction project will be based.
The charge to the augmented PAC workshop will be similar to that given to PAC18. A draft of that charge is as follows:
- Comment on the intellectual framework presented for the 12 GeV pCDR. Is this the best way to present the science case to DOE and to the larger nuclear physics community? Are there flaws or omissions in the framework?
- Review the new research programs that are under consideration for being highlighted in the executive summary of the pCDR. Do they represent compelling science that must be done to advance our understanding of nuclear physics? At what level should they be included in the executive summary?
- Have we omitted any key science initiatives that could be supported by a 12 GeV electron beam?
- Is the experimental equipment proposed well matched to the key physics experiments motivating the upgrade? In cases where an experiment or program is proposed for more than one set of equipment, are the differences in capability and physics reach of the equipment essential for getting all of the physics, important for getting as much physics as possible, or simply useful in that, for example, an experiment could be done somewhat faster with one hall equipment compared to another?
The intellectual framework that will be presented as a starting point for PAC discussions will correspond to that presented in the White Paper and outlined in some detail in its introductory chapter. As a reminder that text is reproduced below:
The facility will make profound contributions to the study of nuclear matter. In particular, it will allow breakthrough programs to be launched in two key areas:
- The experimental observation of the QCD flux tubes which cause confinement. Theoretical conjectures, now confirmed by lattice QCD simulations, indicate that the most spectacular new prediction of QCD -- quark confinement -- occurs through the formation of a string-like "flux tube" between quarks. This conclusion (and proposed mechanisms of flux tube formation) can be tested by determining the spectrum of the gluonic excitations of mesons.
- The measurement of the quark and gluon wavefunctions of the nuclear building blocks. A vast improvement in our knowledge of the fundamental structure of the proton and neutron can be achieved. Not only can existing ``deep inelastic scattering" cross sections be extended for the first time to cover the critical region where their basic three-quark structure dominates, but also measurements of new ``deep exclusive scattering" cross sections will open the door to a new, more complete characterization of these wavefunctions by providing direct access to information on the correlations among the quarks.}
In addition to opening up these qualitatively new areas of research, the Upgrade will:
- Open important new research domains in key areas already under
investigation. These new research thrusts include:
- Determining the dynamics underlying the quark-gluon wavefunctions through measurements of the high-momentum-transfer behavior of form factors.
- Mapping out and understanding the transition from the hadronic to the quark-gluonic description of strongly interacting matter through the study of low-energy duality.
- Searching for the onset of color transparency effects in the region where they are supposed to exist.
- Determining the role of color polarization effects in the NN force by measuring the threshold yN cross section.
- Executing a unique and global study of short-range correlations in nuclei.
- Examining the role of quark masses in determining hadron spectra by mapping out the currently obscure spectrum that straddles the boundary between the rigorously understood heavy-quark systems and the poorly understood light-quark world.
To carry out its job, the PAC, augmented by selected scientists (mainly members of PAC22 who have "retired" from the PAC, but who have a great deal of background and knowledge about the 12 GeV upgrade), will begin by hearing a series of talks in open public session. These talks, which will probably be taking place Friday January 17 and/or Saturday January 18, will include the following:
- Introduction to the Problem at Hand (L. Cardman) - i.e., why are we here and what do we hope to accomplish?
- A Review and Summary of the "White Paper Approved" Major Physics
Thrusts developed with the input of PAC18, with an emphasis on enhanced
science motivation and technical capability, in so far as they improve
physics, since the White Paper was written.
- GlueX (tbd)
- High-x (summarizing experiments in all halls) (tbd)
- GPDs with emphasis on DVCS (summarizing experiments in all halls) (tbd)
- A summary of other initiatives already included in the White Paper (high Q2 form factors, duality, color transparency, etc. - see the list above) (tbd)
Note that the speakers for these sessions will be "appointed." We solicit your suggestions for names of persons to give each of the four presentations (a-d) to the PAC, with the aim of reaffirming and strengthening the science case that has already been made.
- Following the above overview of the status of previously-identified physics initiatives, the PAC will hear presentations by spokespersons for physics programs which proponents would like to elevate in significance (i.e. priority) in the pCDR relative to its place in the White Paper (as reproduced above) and, in addition, on physics that was not presented in the White Paper but which proponents would like to see added to the pCDR. These presentations will be, in effect, "proposals" for changes in the structure of the executive summary of the pCDR (changes relative to the structure in the White Paper). This note is, in effect, a "call for requests for presentation time" before PAC23 by any group that would like to effect such a change. If there are too many such presentations we may request that some groups generate "combined" presentations for related physics programs. The object of this exercise is NOT to "stake out" claims on science to be carried out using the upgraded CEBAF - rather it is to fully develop and peer review the overall science case for the upgrade. We will hear detailed proposals for 12 GeV physics programs following "standard" PAC procedures once the construction project has been approved and is moving ahead formally. Also, please note that in order to be considered for presentation, you must be discussing a research PROGRAM, not just an individual experiment.
- Following the public presentations, the PAC will go into closed session (moving to the Outer Banks) to discuss the science they heard and to have presentations by representatives of each hall on the status of the equipment plans, and a presentation of the "experiment/equipment matrix" that is currently being developed by the JLab Technical Advisory Committee (the same group that does the technical reviews of each PAC proposal). The aim of this presentation will be to summarize the mapping of the different experimental programs onto the equipment in the different halls.
- The PAC will then produce a short summary report (in the style of the report done by PAC18 for the White Paper) that will address the charge presented above and which will become a public document.
If you are interested in making a presentation to the PAC23 review of the pCDR material, please contact Larry Cardman by email (firstname.lastname@example.org) no later than December 2, 2002, identifying the program you want to present, your intention for its "place" in the science outline, and providing a brief paragraph outlining the case you intend to make (roughly the equivalent of the typical abstracts for PAC proposals). You will not be required to make a written proposal to the PAC - rather it is assumed that the relevant written material for what you are presenting is already included in one or more of the hall specific draft pCDRs. You will be asked to leave copies of the viewgraphs of your presentation with the PAC for its perusal during the retreat. We will notify you by December 16 whether your presentation will be included in those to be made before the PAC.
It is our intent that the PAC review will provide an essential element in the process of editing the hall-specific pCDRs into a complete pCDR that outlines the entire science case for the Upgrade in a manner that is both compelling and, in effect, has been peer reviewed by the PAC. Once the PAC review has been completed, the Hall Leaders and selected individuals will review the draft text, enhance and/or edit it as appropriate, and begin the process of merging the draft documents from the halls. In particular, relevant portions of the science sections from each hall will be given to "committees" charged with writing each science subsection of the final pCDR so they can begin the "consolidation" effort.