SLAC Today logo

From the PPA Director
The P5 Report: What Does It Mean for SLAC?

Over the past five months, a select committee of high energy physicists dubbed the Particle Physics Project Prioritization Panel (P5) has been hard at work mapping out the future of high energy physics in the United States. This committee had a very difficult job—under a variety of funding scenarios, some rather stringent, they sought to define a program that addressed a broad range of exciting physics opportunities for the field, while also maintaining the health and vitality of the community and its major laboratories. Just last week, P5 released its final report. In general, it provides “good news” for SLAC. The panel's recommendations are roughly consistent with the strategy we have been pursuing in the Particle Physics and Astrophysics (PPA) Directorate, and several of the explicit projects that we have proposed for our future program received strong endorsement in the report.

P5 was reconstituted in January by the High Energy Physics Advisory Panel (HEPAP), after HEPAP received a charge from the Department of Energy (DOE) Office of High Energy Physics and the National Science Foundation to help develop a plan for U.S. particle physics over the next decade. The Chair of P5, Charlie Baltay from Yale University, was actually in residence here at SLAC visiting the Kavli Institute for Particle Astrophysics and Cosmology during the entire time that the panel was deliberating. In addition, SLAC PPA Professor Tor Raubenheimer and Stanford Physics Professor Stan Wojcicki were members of P5. As a result, many of us at SLAC had the opportunity to interact with the panel and keep abreast of its progress.

P5 was asked to look at four basic funding scenarios:
A. Constant funding at the FY2008 level
B. Constant funding at the FY2007 level
C. Doubling of the budget over ten years starting in FY2007
D. Additional funding above the previous level, associated with specific activities needed to mount a leadership program

Because of the huge cut in funding (~14%) that Congress levied on the field in the FY08 budget, Scenario A is the most restrictive. P5 tended to focus their attention on Scenario B, which many of us consider somewhat optimistic, but not inconsistent with the range of budget possibilities we are likely to face in the coming years. They then discussed the impacts on that plan under Scenario A, and the additional opportunities that would be presented under Scenarios C and D.

The physics program outlined by P5 covers three main “frontiers” of investigation: The Energy Frontier—where collider experiments are used to discover new particles and directly probe the architecture of the fundamental forces at higher energies than have ever before been achieved; the Intensity Frontier—where intense particle beams are used to uncover the properties of neutrinos and study rare processes that may provide clues to new physics; and the Cosmic Frontier—where underground experiments and telescopes are used to study the nature of dark matter and dark energy, and to detect ultra-high energy particles from space. These three frontiers were all deemed crucial to further progress in the field, and a variety of experiments in each category were evaluated and comparatively ranked.

As indicated above, the results look good for PPA at SLAC. For the Energy Frontier, P5 recommended continued strong support for the U.S. participation in the Large Hadron Collider (LHC) experiments at CERN including U.S. involvement in the planned detector and accelerator upgrades, under all of the funding scenarios considered. PPA physicists are heavily involved in the ATLAS experiment at the LHC and are engaged in the accelerator commissioning. We are proposing an expanded SLAC role in both the ATLAS and machine upgrades, foreseeing leading roles in the upgrades of the tracking system, data acquisition and trigger system, and a greatly expanded role in supporting physics analysis. With first data just around the corner, the physics discovery opportunity of the LHC is poised to define the future of the field.

For the Intensity Frontier, P5 recommended R&D towards an intense proton source. The SLAC L-band rf source development program that was started in support of the International Linear Collider (ILC) would be an important element of such an R&D effort. Already, SLAC is planning to deliver rf components to Fermilab in FY09 to support planned cryomodule tests. In addition, P5 recommended that significant U.S. participation be pursued under Scenario B in an overseas “super flavor factory”—a higher intensity version of SLAC's B-factory. SLAC detector and accelerator physicists are playing important roles in the conceptual design of the SuperB facility planned for construction near Frascati in Italy.

Finally, for the Cosmic Frontier, P5 recommended a vigorous program of underground physics experiments at the Deep Underground Science and Engineering Laboratory (DUSEL), including searches for the direct detection of dark matter and neutrinoless double-beta decay, two areas in which SLAC and Stanford have been especially active. In addition, they explicitly endorsed both the Joint Dark Energy Mission (JDEM) and the Large Synoptic Survey Telescope (LSST) experiments under all scenarios. SLAC is playing a key role in the SuperNova Acceleration Probe (SNAP) concept for JDEM, and leads the DOE involvement in LSST.

P5 also recommended a broad program of accelerator R&D directed toward the energy frontier, including several projects that are being pursued at SLAC: Work on technologies for the ILC, high-gradient normal conductor accelerator research, plasma acceleration and other aspects of basic accelerator science. The report comments that unique core competencies in accelerator research exist at SLAC and some of the other laboratories, and these must be maintained even as high-energy physics experiments are shut down at these labs.

Of course, the P5 report is not the end of the story. It still remains to be seen how the Office of High Energy Physics at the DOE will respond to these recommendations, and how the budget picture for this field will emerge over the next few years. Nevertheless, it is encouraging to see that the strategy we have taken in PPA is resonating well with the federal advisory process.

The entire P5 report can be down loaded from the DOE website.

—Steven Kahn, SLAC Today, June 13, 2008

Steven Kahn is SLAC's Director of Particle Physics and Astrophysics (PPA).