All Hail Resonaances

I’m delighted to see Jester back in action, providing great material on the current state of HEP physics, with, over the past week and a half:

  • A sober look at the sparse prospects for near-term (i.e. 2014) input from experiment, with the Planck CMB polarization results one of the few things for which there are significant expectations.
  • An equally sober look at the problem of making the case for a 100 TeV collider, given that this will be the first time people don’t have a “no-lose theorem” showing that something new has to turn up in the new energy range being explored (of course the argument that it’s an unexplored new energy range remains an excellent one by itself for the exploration). About the arguments Arkani-Hamed is making, Jester has:

    Nima’s idea that we need a 100 TeV collider to prove that SUSY fine-tuning is larger than 0.01% is good. As a joke to relax the atmosphere. Certainly, the case for the new collider can be made stronger than that.Some ideas that are being bandied around are precision Higgs physics, double Higgs production, rare Higgs and top decays, non-perturbative electroweak effects, or WW scattering. These topics can be made more concrete and several more items can be added to the list.

  • To give us all some hope, he has some news about a possible astrophysical X-ray spectrum signal that could conceivably be evidence for a sterile neutrino dark matter candidate. Right-handed neutrino fields fit naturally into the SM pattern of fundamental fields, but with zero SU(3)xSU(2)xU(1) charges. That such fields have something to do with dark matter looks more promising than the SUSY or axion proposals of introducing a new and different sector of fields. My knowledge of neutrino physics isn’t what it should be, so I’d be curious to hear of good references about the sterile neutrino dark matter issue.

Update: For some idea of the case being made for a larger collider, one might want to take a look at talks in Beijing a few days ago, where there’s a proposal for the Chinese to build it. Talks at a conference are here, and last Sunday there was a big event featuring Yau, Gross, Witten, Arkani-Hamed, ‘t Hooft, Maiani and Incandela, video here. On the whole people seem to be pretty much sticking to making the generic case for high energy, not promising superpartners or extra dimensions this time.

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19 Responses to All Hail Resonaances

  1. Per says:

    I work in hep-th and there is nothing I’d love more than to find experimental evidence for SUSY.

    However, I still don’t thinks its economically motivated to build a 100 TeV collider. There are other scientific areas which are more important, for example fusion and renewable energies. While funding in one field does not by necessity exclude funding in another, a mega project like a 100 TeV collider will cause huge deficits in other fields.

  2. nolose says:

    No lose?
    For the LHC, certainly, there were very strong indications that it would discover the Higgs boson. The Standard Model had already been vindicated in great detail while the LHC was in its design stages.

    The Tevatron was not “built to discover the top quark.”
    The Tevatron was built to reach an energy of 1 TeV/beam, to explore what was out there. Note also that PEP, PETRA and TRISTAN were all built to discover the top quark.

    LEP was built to discover supersymmetry?
    Speak to Burton Richter about what he said to the CERN management circa 1981 about building an e+e- collider on the CERN site. CERN had built only hadron machines up to then.

    The SppS was certain to discover the W and Z bosons.
    This is a bit complicated. The SPS was a fixed target proton synchrotron. Once the masses of the W and Z had been estimated (indirectly) by other experiments, then there was a case to convert the SPS into a p-pbar collider. This was the stochastic cooling story, etc. But the SPS needed to be there first, and the SPS was not built to discover the W and Z bosons. Note also that Rubbia, Cline and Peter McIntyre proposed the stochastic cooling idea to FNAL first, to convert the Fermilab Main Ring into a collider to produce the W and Z bosons, and they were kicked out. The Tevatron came online in 1985, after CERN had already discovered the W and Z bosons, and before anyone had any firm estimate of the top quark mass. (And Rubbia did discover the top quark at the SppS, at a mass of 44 GeV/c^2.)

  3. Daniel Rocha says:

    These guys propose using the abandoned tunnels of SSC (45%) to build a 100TeV collider for the cheap price of ~1.5billion$

    It’s an interesting read.

  4. Peter Woit says:

    Daniel Rocha,
    They’re talking about two colliders, a 240 Gev electron-positron machine in the SSC tunnel, and a 100 TeV hadron machine in a completely new 270 km tunnel. I don’t see where you get $1.5 billion, the only cost numbers I see there are for $1.32 billion for a 270 km tunnel and $740 million or $1.9 billion just for the cost of the wire for the magnets in that tunnel.

    The order of magnitude for this scale machine is likely to be $20 billion, and I don’t see how building the thing really huge with lower field strength magnets is going to dramatically reduce the cost. You then need to instrument a 270 km long experimental apparatus.

    It seems within the realm of believability that CERN might be able to fund something on this scale over the next 20-30 years. The chance of this happening in the US I think is zero.

  5. Don Murphy says:

    Here is a post by Matt Strassler that gives some information and references on the X-ray spectrum you mentioned that may have something to do with dark matter:

  6. A few references on the subject of neutrino dark matter (from my library, but I’m not an expert on this). See [1] for a set of lectures on the astronomical signatures of ~keV scale neutrino dark matter. [2] is an extensive review of the nuMSM = “neutrino minimal standard model”, the absolute minimal model with sterile neutrinos and nothing else coupling to the SM below the Planck scale. [3] is a shorter presentation of the essential points by the same authors.

    For a broader review of right handed neutrino pheno that is not wedded to the nuMSM or a particular dark matter scenario see [4]. See [5] for a “model builder’s guide” and [6] for a feasibility study on collider experiments to explore the whole range of sterile neutrino masses below a few GeV.

    Finally, I would just like to point out that Shaposhnikov, one of the authors on the nuMSM papers, correctly predicted [7] (with Wetterich) the Higgs mass on the basis of: a) no new physics coupled to the SM fields between the weak and Planck scales and b) asymptotically safe gravity. It’s interesting that the idea works so well.

    Surely you’ll have no trouble navigating the literature, but I hope this helps a little!


    [1] H. J. de Vega and N. G. Sanchez, (2013).

    [2] L. Canetti, M. Drewes, T. Frossard, and M. Shaposhnikov, Phys. Rev. D 87, 093006 (2013).

    [3] L. Canetti, M. Drewes, and M. Shaposhnikov, Phys. Rev. Lett. 110, 061801 (2013).

    [4] M. Drewes, Int. J. Mod. Phys. E 22, 1330019 (2013).

    [5] A. Merle, Int. J. Mod. Phys. D 22, 1330020 (2013).

    [6] S. N. Gninenko, D. S. Gorbunov, and M. E. Shaposhnikov, 20 (2013).

    [7] M. Shaposhnikov and C. Wetterich, Phys. Lett. B 683, 196 (2010).

  7. Peter Woit says:

    Thanks Michael!

    That’s very helpful.

  8. bobby3 says:

    Regarding the new collider arguments, that debate between Strassler and Gross at the end of Strassler’s recent talk (at KITP) was pretty entertaining.

  9. justin says:

    perhas this is off topic, but is this result indication of non-standard physics?

  10. Peter Woit says:

    I noticed that, Gross seemed remarkably testy. The fact that he just spent a couple days on planes traveling to Beijing to try to help sell the Chinese on the 100 TeV accelerator idea might explain his reaction (overreaction, I think…) to some of Strassler’s comments.

  11. M.Wang says:

    Is there a link to the Strassler/Gross debate?

  12. Peter Woit says:

    I don’t know if you could call it a debate, but the exchange was in the question section after this talk

  13. paddy says:

    The Strassler KITP talk is both informative and impressive. Thank you bobby3 and Peter Woit.

  14. Zathras says:

    On the 100 TeV collider post, there is a comment by someone named Andrew which is so dead-on that I am going to just copy and paste it here:

    “A 100 TeV collider would be nice. So would a pony. I would prioritize about half a dozen other investments before that, however:

    1. $100-$500 million for improved computing power to do lattice QCD calculations both to make theoretical predictions that reduce the MOE (especially for discriminating between backgrounds and signals), and increase the power of existing experimental data and new searches with the same equipment, and would allow more precise extraction of Standard Model constants from existing data. We are pretty much guaranteed to be able get seven or eight loop QCD beta functions (the current research effort is devoted to five loops and each successive term gets much harder than the one before it to calculate) and with more accurate calculations, greatly increased theoretical precision, for example, simply by investing the money to get the computational power to do the job.

    2. $1-2 billion for deep space satellites. The only thing we can be absolutely exists in terms of BSM physics is something to explain dark matter phenomena, either at least one new particle or at least one new force or both. The best way to narrow the dark matter parameter space is with precision astronomy observations that the atmosphere obscures, not with a 100 TeV collider. We can be vastly more efficient in our search for dark matter particles at some future experiment yet to be designed if we use astronomy observations to more tightly narrow this parameter space first. It is the difference between looking for a face in a crowd based on a photograph v. a police sketch artist’s effort from an eye witness’s blurry recollection. We can also, for example, much more accurately triangulate star distances with a pair of distant deep space satellites which would calibrate all other astronomy observations. And, better observations of neutron stars, pulsars, cosmic rays, etc. provides a different way of doing super high energy HEP with nature paying the electric bills for it. Also, realistically, the only application of 100 TeV+ scale phenomena is cosmology anyway. Very early universe observations from deep space also narrow the parameter space of 100 TeV scale physics and let us know what we should be looking for.

    3. $2-3 billion+ for neutrino physics experiments (e.g. astronomy, reactor, neutrino beam, double beta decay). A little more investment here to pin down the last few Standard Model parameters and determine things like the Dirac v. Majorana basis of the neutrino mass has an immense impact on the parameter space of BSM physics.

    4. Continued funding of B factories. There are dozens of meson resonances that we don’t really understand well. This is an area of particle physics where predictions are frequently not matching up with experimental results. You don’t need a 100 TeV collider to investigate, e.g., 0.5 to 2.5 GeV scalar and axial vector mesons.

    5. $100-500 million or so to push the envelope on exclusions for proton decay, magnetic and electric dipole moments, non-collider based axion field searches, entanglement experiments, etc.

    6. $100-$200 million on non-SUSY/non-stringy theoretical work. We have all of our eggs in one or two baskets. The LHC has cracked many of the other contenders. Like anything, there is declining marginal benefit to funding yet another SUSY theorist.

    If there is money left over, then by all means, lets go buy a 100 TeV collider.

  15. Peter Woit says:

    I don’t see much reason for this kind of argument worrying about a 100 TeV machine crowding out funding for other worthwhile experiments. In the US, I see absolutely zero chance of any funding of a machine like this, the funding decisions for the forseeable future all involve deciding between projects like the ones mentioned in the comment.

    Similarly, in Europe any prospects for building a machine like this are a long way off, with the current plan to operate the LHC until 2035. The discussion about the future and a 100 TeV machine is about what to fund 20 years from now, not what to fund now.

    It’s only in China that I see any conceivable possibility of someone starting to fund this kind of project in the next 10-20 years, and there the argument to the Chinese government is for special funding for this particular project. If they do decide to do it, it would not necessarily conflict with them providing some of the much lower levels of funding needed for the projects in the comment. And if they don’t decide to do it, you can ask people who were around in US-HEP when the SSC was cancelled to tell you how that caused the rest of the field to flourish amidst an abundance of resources…

  16. nasren says:

    My take on the Strassler-Gross discussion at the end of the KITP talk.

    Strassler: We need to think differently.

    Gross: No, let’s just keep thinking the same!

    I thought Matt Strassler was just saying (pretty clearly) we should look for other ways to consider experiments for BSM physics, other than building a higher energy collider. And Gross’ response seemed to be that we shouldn’t do that. It seemed like a bad misunderstanding — the strange thing was that others in the audience seemed to share it. My guess is that they were miffed by a different point (and then transferred it over) which was that supersymmetry has not made an appearance so we should consider other ideas.

    I thought Nima’s talk was very interesting — a great pity that the discussion was cut off at just the point where the weakness was about to be exposed.

  17. Peter Woit says:


    Strassler makes the case for a 100 TeV collider here in his latest blog entry

    I was surprised at Gross’s reaction, since I figured Strassler obviously was in favor of a higher energy machine, just arguing that there were good reasons to also look elsewhere. Looking back at the talk, I think Strassler’s comment that pure SM behavior at the LHC would be circumstantial evidence against string theory (not really controversial, since SUSY at the LHC was always argued to be the most likely circumstantial evidence for string theory) was what set Gross off. He and others are tempted to try and argue that there’s no major problem with the SUSY/string theory paradigm collapsing, we just need a bigger accelerator, but I don’t think that’s going to fly and they’re starting to realize this.

  18. CU Phil says:

    I took Gross to be arguing something that I’ve heard both from people who think that all we need is a bigger accelerator, and people that think that the motivation for low-energy SUSY was weak from the word go: that, on reflection, perhaps naturalness wasn’t as good an argument for SUSY as we thought. People like Gross go on to argue that the failure of naturalness doesn’t mean we should give up on SUSY, since there are other arguments for it, while the other group who gives this argument concludes that we probably should have been looking elsewhere earlier, but we definitely ought to start start now. Gross seemed to place Strassler in the latter camp, even though he explicitly is not.

  19. Shantanu says:

    Peter, I disagree that the cancellation of SSC did not benefit other fields.
    I know that when SSC was cancelled many people whow were working on SSC
    switched to LIGO and also neutrino experiments (and probably other astroparticle
    experiments which I am not aware of). So even though I agree that there is no evidence
    that SSC cancellation increasing funding in other fields, certainly other fields
    did benefit from more manpower/expertise of those who worked on SSC.

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