News from the High Energy Physics Advisory Panel

By Mel Shochet, University of Chicago, HEPAP Chair

(Originally published in January 2010 DPF newsletter)

The High Energy Physics Advisory Panel (HEPAP) advises both the Department of Energy and the National Science Foundation on the current and future program in elementary particle physics. Meetings are held three times per year in or around Washington, D.C. The agencies give reports on their activities, often focusing on budgetary issues but also including upcoming projects, recent successes, and current problems. Presentations are also made on topics of importance to the field, including future projects, R&D efforts, and the work

of international committees. Following each meeting, I write a letter to the agencies summarizing the meeting and giving HEPAP’s comments. Those letters as well as meeting presentations and HEPAP reports are available on the website

The most important HEPAP task is providing guidance for the future program. This usually takes the form of a report issued by a HEPAP subpanel and approved by HEPAP. Each subpanel is created on an ad hoc basis to address a specific charge from the agencies. It ranges from a narrow focus, like dark matter experiments or advanced accelerator R&D, to a broad charge to develop a ten-year program for the entire field. Recent HEPAP subpanel reports were written by the Neutrino Scientific Assessment Group, the Advanced Accelerator R&D Subpanel, the Dark Energy Task Force, the University Grants Program Subpanel, and the Dark Matter Scientific Assessment Group. For many years there have been periodic broad planning exercises carried out by HEPAP subpanels. In 2002, one chaired by Jon Bagger and Barry Barish recommended that a more regular process be carried out by what they called the Particle Physics Project Prioritization Panel (P5). Since that time there have been three such subpanels, two chaired by Abe Seiden and the most recent one, in 2008, chaired by Charlie Baltay.

The 2008 P5 subpanel was charged with developing ten-year programs under four budget scenarios: less than flat in constant dollars, flat over the decade, an increase of approximately 3% per year in real terms, and an ordered list of important projects requiring additional funding. They heard presentations on current and proposed projects, and they gathered community input through letters and town meetings held at SLAC, Fermilab, and Brookhaven. In their report, they organized the field by the tools we use: the Energy Frontier for experiments requiring high energy colliders, the Intensity Frontier for projects that need intense secondary beams, and the Cosmic Frontier in which particles from the cosmos are studied. Their recommendations have been critical to the development of the DOE and NSF programs.

At the Energy Frontier, the recommended program includes additional running at the Tevatron Collider, strong U.S. participation in the LHC program including upgrades, and broad R&D for a future lepton collider. Since the required energy of such a machine won’t be known until new physics is seen at the LHC, P5 recommended R&D not only for the ILC but also for other technologies such as a muon collider. Advanced accelerator R&D and detector R&D were also strongly supported since that is the seed corn for our future.

The centerpiece of P5’s Intensity Frontier program is a high intensity proton accelerator at Fermilab directing an intense neutrino beam to a large underground detector in DUSEL to search for ν CP violation, proton decay, and supernova neutrinos. The new accelerator would be a stepping stone to a possible future neutrino factory and eventually a muon collider. Also recommended were reactor neutrino experiments to measure θ13, neutrinoless double beta decay experiments, and a set of precision experiments including a μ→e conversion experiment and possible participation in an overseas super-B factory and rare K decay experiments.

In the Cosmic Frontier, the program includes large dark energy experiments in space and on the ground, and dark matter experiments employing different technologies. New large experiments with high energy cosmic rays, gamma rays, and neutrinos could only be carried out under the higher funding scenarios.

The most recent subpanel was the Particle Astrophysics Scientific Assessment Group (PASAG) chaired by Steve Ritz, which presented its report at the October HEPAP meeting. It was charged with recommending a detailed program for the Cosmic Frontier again under a number of budget scenarios. The task was especially challenging because many of the experiments address important scientific questions in both particle physics and astronomy. PASAG prioritized based on importance to our field, leaving the astronomy prioritization to the ASTRO2010 process. The subpanel considered experiments to study dark matter, dark energy, high energy cosmic rays, gamma rays, and neutrinos. The scientific merit of the proposals made selection difficult, especially in the lower budget scenarios. They gave highest priority to dark energy and dark matter, recommending significant funding in all of the budget profiles. Large expenditures for the study of high energy cosmic particles could be included only in the higher budget scenarios.

The next HEPAP meeting will be March 11-12 when we will hear details of the President’s FY11 budget.