The EPP2010 report by the Committee on Elementary Particle Physics in the 21st Century is out today, and it is entitled Revealing the Hidden Nature of Space and Time. This committee was convened to recommend priorities for high energy physics in the U.S. over the next 15 years. Its membership included non-physicists and it was chaired by economist and ex-president of Princeton Harold Shapiro. The inclusion of people from outside the field emphasized the need for wide support for funding of U.S. particle physics if it is to remain healthy. The latest issue of Nature contains an article about the report entitled US particle physics fights for survival, and an editorial Making collider endorsement count. A press release about the report is here.
At the press conference announcing the report (which was webcast), Shapiro emphasized that the non-physicists on the committee had not been fully aware of the difficult situation US particle physics was in. They were very sobered by the state of US HEP, which he described as facing a serious danger that it would be half its size in 4-5 years, as current programs ended without a compelling follow-on program. The most important recommendation of the committee was that construction of the ILC in the US, probably at Fermilab, be vigorously pursued and that:
The United States should announce its strong intent to become the host country for the ILC and should undertake the necessary work to provide a viable site and mount a compelling bid.
Constructing the ILC in the US would require an increase beyond the rate of inflation in HEP funding, and the committee considered a scenario of budget increases of 2-3%per year that would probably be required, although solid numbers for what the cost of the ILC would be are still not yet available. Emphasizing the ILC in this way was described as a “high-risk, high-reward” strategy, and that taking these risks was necessary for US HEP to retain any leadership role in the field.
More specifically, the committee recommended six action items, ranked by priority:
1. Realize the physics potential of the LHC experimental program.
2. Launch a major program of R and D for the ILC, significantly expanding current expenditures on this.
3. Announce US intent to become the host country for the ILC.
4. Increase the current share of the HEP budget devoted to studying dark matter, the CMB and dark energy.
5. Develop a staged program, with international cooperation, of neutrino experiments, with emphasis on neutrinoless double-beta decay, accelerator based experiments, and search for possible charge-parity violation. This last might involve large detectors that could also be used to search for proton decay.
6. Support (especially if they’re not very expensive) high-precision experiments that probe beyond the Standard Model physics, such as a future B factory, lepton-flavor violation and rare-decay studies, searches for electric dipole moments, and precision measurements of muon g-2.
The committee did a very good job of recognizing the difficult situation of US HEP, and coming up with a plausible strategy for how to make the best of it. I have my doubts about whether it’s really a good idea to sell this as “Revealing the Hidden Nature of Space and Time”, since it’s not especially likely that that is what is going to happen. There’s no particularly good reason to believe that extra dimensions will show up at the LHC or ILC energy scales, so over-selling this is dangerous. I do understand that it’s a lot harder to get people excited about the new physics that this is likely to really all be about: understanding the nature of electro-weak symmetry breaking.
This was a study of what to do about experimental HEP, so the problems of theoretical HEP were not addressed. Unfortunately, besides the usual arguments for supersymmetry, over-hyped ideas about string theory make an appearance as the committee calls for “Improved tests of general relativity to search for effects of extra dimensions or string theory” and “Measuring time variation of physical constants with spectroscopy of distant objects to search for effects of extra dimensions and string theory”, without noting that string theory makes no predictions about either of these. One other thing included in the report is new, improved verbiage about the status of string theory. In Witten’s biographical sketch, it is described as “one of the leading candidates for the grand unified theory of elementary particle physics”, which seems to me to be a downgrade from the phrase “the leading candidate” which until recently was often used to describe the status of the theory.
Update: Also from Alexey Petrov, who in a comment at Cosmic Variance links to a very different point of view about prospects for constructing the ILC in the near term: a recent resignation letter from Bill Foster, who was the Proton Driver project leader at Fermilab (the Proton Driver would be a high-luminosity, lower energy accelerator, useful for, among other things, producing a more intense neutrino beam).
Update: More from JoAnne Hewett at Cosmic Variance.
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