Revealing the Hidden Nature of Space and Time

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: More about this from Chad Orzel, Lubos, Clifford Johnson at Cosmic Variance, Tommaso Dorigo and The New York Times.

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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26 Responses to Revealing the Hidden Nature of Space and Time

  1. michael says:

    It’s difficult to comprehend extending our pocketbooks in favor of such laboratories while the NCI budget (i.e. applicable, translational research) is drying up. What is so pressing about understanding the fundamentals of symmetry breaking when troves of Americans are dying daily from the toxicity associated with underdeveloped cancer treatments?

  2. Who says:

    it is possible that you mean “droves” of Americans and not “troves”.

    My dictionary says trove (as in “treasure-trove”) is a thing found, from the old French word to find.

  3. michael says:

    Yes…even probable. Perhaps you could just talk Dr. Woit into building a grammar check into the ‘submit comment’ section?

  4. Peter Woit says:


    There were long discussions of this over at Cosmic Variance. I think the relevant point is that each year the federal government is spending about 2500 billion, of which .7 billion is going to particle physics. This .03 percent of the budget isn’t what is crowding out money for the purpose you mention (or any other purpose), much less the incremental amount over this that the ILC would cost.

  5. anon says:

    Peter, could you clarify for us what your problems with electroweak symmetry breaking are. The jargon probably puts laymen like me off. Perhaps I can explain what I’ve picked up on the subject.

    My understanding is there are four electroweak gauge bosons, the photon and the massive but uncharged Z, plus two massive charged (W+ and W-).

    All four have been detected at CERN in 1983, which validated electroweak theory.

    The problem I think is why of the four only the photon has no rest mass and infinite range at low energy, while the Z, W+ and W- all have very short ranges (giving the weak force which controls the decay of neutrons into protons, etc.).

    The mainstream mechanism is that a Higgs vacuum field gives mass to the Z, W+ and W- bosons at low energies, in some way. At higher energy, ie at the energy of electroweak unification, these bosons are no longer attenuated (or whatever) by the Higgs field, and their range becomes infinite.

    The photon is able to go an infinite distance because it has no rest mass. The Higgs field gives rise to all inertial masses. It hasn’t been detected directly. Is this a reasonable summary?

  6. sunderpeeche says:

    The EPP report was dedicated to experimental HEP, and it makes no difference if there are a few statements about string theory (or any other theory). The decision to fund the ILC etc will be based on criteria far removed from “will this validate string theory or not”.

  7. Tony Smith says:

    Peter said “… The … report by the Committee on Elementary Particle Physics in the 21st Century … was a study of what to do about experimental HEP … the problems of theoretical HEP were not addressed …”.
    sunderpeeche said “… The EPP report was dedicated to experimental HEP, and it makes no difference if there are a few statements about string theory (or any other theory). …”.

    anon said “… CERN in 1983 … validated electroweak theory …”.

    A generation ago, high energy physics experiment and theory were so closely linked that you could not really discuss one without the other, leading to results such as validation of electroweak theory.

    The fact that the EPP report is about experiment and “… it makes no difference if there are a few statements about … theory …”,
    is a clear condemnation of the present-day state of conventional theoretical high energy physics = superstring theory, and of this generation of conventional high energy physics theorists.

    That condemnation is emphasized by the fact that “… The principal charge to the Committee on Elementary Particle Physics in the 21st Century was to recommend priorities for the U.S. particle physics program for the next 15 years …”, which charge was to study ALL of Elementary Particle Physics.
    That the EPP report was “dedicated to experimental HEP” is a de facto statement by the committee that present-day conventional theory = superstring theory is irrelevant.
    (It would be nice to be able to say that irrelevance = mostly harmless, but unfortunately that is not the case.)

    Tony Smith

  8. sunderpeeche says:

    Bravo Tony Smith! A condemnation of current theory … I hadn’t really thought of it that way … but still.

    However, the fact is also that (as has been noted in this blog before), expt HEP simply hasn’t (definitively) found anything beyond SM since the mid-1970’s. The new machines simply *have* to be search-and-discovery machines, not linked to tests/validations of any theory
    — and this is *not* the fault of string theory. (FWIW it’s not the fault of any theory or expt. Nobody knows the mass scale of the next discovery.) Note that in 1950-60’s there were competing theories, and many expt puzzles. Machines were built to find new things, not always guided by any theory — but there were plenty of questions to ponder, no need to “set priorities”.

    The committee might officially be for all HEP, but theory (apart from supercompters?) doesn’t need (much?) capital infrastructure. No need for a committee.

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  10. SomeBody says:

    A billion here, a billion there, soon you’re starting to talk real money:

    The Gross National Debt

  11. JoAnne says:

    Peter, thanks for providing a good summary of the contents and the purpose of this report. Alot of people worked very hard to get the non-HEP scientists and non-scientists on this panel excited about our science. It seemed to have worked and the positive statements in this report have the potential to do HEP a tremendous amount of good.

  12. Peter Woit says:

    Thanks Joanne,

    Good luck with the hard work over the next few years that will be needed to convince people to support US HEP. There are very good reasons for people to be interested in this kind of science and want to see it supported, the report does a good job of explaining this.

  13. steve says:

    From a political point of view, I question putting all the eggs in the international basket. Americans tend not to support large-scale collaborations of this type (with the unfortunate exception of the space station), and given current international opinion I think it could be hard to get foreign countries to agree to a US site.

    It might make more sense to stoke insecurities about falling behind foreign countries in HEP. Americans respond better to a chance to compete and win. There’s a big psychological difference between a) inviting collaboration from all over the world on a mostly-US project and b) fighting to get permission from foreign countries to host an international project. The latter smacks a bit too much of cities bidding for the Olympics, which is also often unpopular. It may seem stupid, but I think wanting to stay ahead of other countries is a pretty strong motivator for funding of basic research. Even when we do it by attracting people from other countries.

  14. sunderpeeche says:

    The opening sentence of the EPP Executive Summary talks of “US global leadership in science, technology…” Next para “By recognizing the need for US leadership in particle physics…” Third para “… US tradition of leadership in the field is not secure” (tradition? post-WW2 maybe)

    Language like this is not going to impress foreign collaborators (for ILC). Why would Japan/China/Europe/… collaborate to establish (or perpetuate) “US leadership”? On the other hand, the US Congress is unlikely to fund a project not sited in the USA. Not so simple. US may have to be prepared to fund entire “I”LC.

  15. My two pence on the “US leadership” issue:

    I think the attitude of us non-americans working in HEP would improve a lot if the US stopped talking about themselves as the owners of the field.

    A committee of americans talking about how to steer US HEP into a leadership role is fine – nothing to object. But it should not be a public document, as if seeking agreement from international collaborators. It is slightly annoying since it gives the -IMO wrong- idea that the US has entered the LHC experiments in forces to do science there for a long time to come, bringing experience and money, but with the secret aim of finding the right moment to stab their collaborators on the back, win support for an american ILC, and march back home triumphantly.

    Why can’t we form a committee who deals with a more important issue: how to dodge the need to tickle the ego of a few dumb congressmen in order to survive ?
    I am sure 90% of US scientists would be happy to live without having to be the kings of the hill in HEP. Let me rephrase it: without the need to put “leadership” as a deliverable in all their requests for funding…

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  17. Tony Smith says:

    Tommaso Dorigo, about EPP2010 and ILC, said “… I think the attitude of us non-americans working in HEP would improve a lot if the US stopped talking about themselves as the owners of the field. …”.

    I completely agree. That was one of the two major factors that killed the SSC (the other being failure to honestly state and control costs). Back in the SSC days a German friend of mine said something like:
    “… The Americans expect us to put a lot of money into the SSC, but they want every proton in the SSC to carry a little American flag. …”.

    Tony Smith

  18. sunderpeeche says:

    About the SSC, absolutely yes. (My friend wasn’t German, but no matter.) The machine was conceived (after the cancellation of ISABELLE) to “bring back the lead the US”, “highest energy particle accelerator back in the US”. Why would foreigners support such a project (as they were later asked to do)? If the ILC is also to “maintain/restore US leadership in HEP” why will others support it?

  19. SomeBody says:

    Isn’t the best location for the ILC, should it really be built, the most successful, most international particle physics lab on the planet ever? I.e. CERN? There’s much to be said for the Swiss hosts, not least their lack of interest in claiming world leadership based on physical location of this or that machine or building. And there are some pretty good restaurants in Geneva, too.

  20. from EU says:

    The ILC collider employs the standard accelerator technique and aims at reaching an energy of 0.5 TeV around 2020. This would be a poor improvement over the LEP collider, that reached 0.2 TeV in 2000.

    Even if LHC will indicate that 0.5 TeV is enough to access new physics, and even if US particle physics needs ILC to survive, it would be better to wait until a linear collider can be built starting a new, more promising, technique (e.g. CERN is trying to develope CLIC).

  21. sunderpeeche says:

    The ILC does not employ “standard” accelerator technology, as if were off-the-shelf stuff. It is very demanding technically. Still a challenge to figure out how to deal with the heat load, radiation hazards etc. A brief history (which anyone is free to dispute): after the SLC was the idea for a 1 TeV x 1 TeV linear collider (TLC = TeV Linear Collider). This proved too ambitious, scaled to 0.5 x 0.5 TeV (TLC = TeV c-o-m linear collider). This was mooted for a while, evolved to NLC (Next Linear Collider), whatever might be achievable/fundable ~ 250 x 250 GeV (these were all pure US projects). Japan developed idea for JLC (you figure it out). CERN worked on CLIC, others on TESLA (~TeV Superconducting Linear Acc). The various ideas (maybe not CLIC) merged into ILC, which is 0.5 TeV c-o-m ~ NLC. But still many unsolved technical challenges.

  22. from EU says:

    dear sunderpeeche,

    the German, US and Japanese projects are “standard” in the sense that they all aim at an acceleration gradient of “only” about 20 MeV/meter, such that an “ultimate” linear accelerator (about 2 x 30 km long) is needed to reach 500 GeV.

    If we hope to someday reach larger energies, we should start trying a shorter accelerator with a larger gradient. CLIC aims at about 150 MeV/meter: even if CLIC will not seem faster nor cheaper than ILC, I would consider CLIC as the most promising option.

  23. sunderpeeche says:

    Tell that to the designers of the ILC. People have been trying to design a next-generation linear collider for ~ 20 years now. I expect that if they could do better than 20 MeV/m they would.

  24. sunderpeeche says:

    It’s not exclusively a matter of the accelerating gradient. The positron source is another problem. Typically one smashes an electron beam onto a target, and positrons come out (along with junk). Usual target choice is copper (dissipates heat well) or tungsten (v high melting point), but for ILC requirements all known solutions will melt. Current thinking (as far as I know) is to spray a mercury jet across the e- beam, collect the spent mercury — it is a liquid — and recycle it (via heat exchanger or something). Raises safety/health problems with mercury vapor leakage etc. Not clear the idea will work. Never been done. Don’t know if prototype exists.

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