SUSY 2013

The big yearly SUSY conference, SUSY 2013 has been going on in Trieste this past week. From the experimentalists, the news is just stronger limits: no hint of SUSY anywhere in the LHC data. From the theorists, the reaction to this news has been pretty consistent: despite what people say, not a problem.

According to John Ellis, everything is fine, with MSSM SUSY preference for a Higgs below 130 GeV vindicated and successful SUSY predictions for the Higgs couplings (that they should be the same as if there were no SUSY). According to Ellis, we just need to be patient, and he has CMSSM fits preferring 2 TeV gluinos.

However, if you look at Savas Dimopoulos’s talk the MSSM gets a grade of D-. He argues that the LHC has shown us that the answer is the Multiverse, and that split SUSY with its fine-tuning gets a grade of A. The grade inflation in particle physics is pretty dramatic: you now can get an A without your theory having the slightest bit of experimental evidence.

Nima Arkani-Hamed’s talk was about SUSY in 2033, which in his vision will be pretty much the same as SUSY in 2010. Remember all those things the LHC was supposed to find but didn’t? Well, now the argument is that they’re really there, but we will need a 100 TeV collider to see them. If all goes well, in 2033 such a machine will be under construction, and SUSY 2033 could feature all the SUSY 2010 talks retreaded, with 1 TeV gluinos moved up to 10 TeV.

One of Arkani-Hamed’s slides makes me worry that the LHC results have caused him to begin to lose his marbles. He claims that if one doesn’t see new physics like SUSY at the 100 TeV machine, in his view

this would be 100 times more shocking and dramatic than no nothing but Higgs at the LHC

[I initially misread and misquoted this, my apologies. The claim was not that no BSM at 100 TeV would be 100 times more shocking than no Higgs at the LHC, but that it would be 100 times more shocking than no BSM at the LHC. So, the usual sort of over-the-top exaggeration, but not crazy.]

Even wilder claims came form Gordon Kane in his talk, where we’re told that particle theorists giving “negative” talks because of the LHC results have:

no knowledge of LHC physics, Higgs physics, supersymmetry, phenomenology, etc.

According to Kane, we not only have seen the tip of the iceberg of a unified string/M-theory, but actually have the whole iceberg. The ingredients are all in place for what he sees as a similar experience to the 3 year period in the 1970s when the Standard Model emerged and was experimentally vindicated.

Tommaso Dorigo points out that there was one SUSY 2013 talk that in his humble opinion was a good candidate for the IgNobel, see here (warning, NSFW).

On a more positive note, at the conference production of compactified Calabi-Yaus was finally conclusively demonstrated.

Update: Nathaniel Craig has some recent lectures on The State of Supersymmetry after Run I of the LHC. The emphasis is on examining the consequences of failure of pre-LHC assumptions about SUSY based on simplicity and naturalness. Out of 60 or so pages, only one is devoted to the models favored by Arkani-Hamed and Dimopoulos, string-theory based models are not even mentioned.

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20 Responses to SUSY 2013

  1. Bee says:

    I once had to sit through a talk where “Susy” was depicted by Betty Boop. Gives you a totally new perspective on what the guys are after.

  2. emile says:

    I went through Nima’s slides (so few this time!). The talk is essentially a sales pitch for the next big machine. I wouldn’t say that his statement on what would be most shocking (no Higgs vs no BSM up to 100 TeV) is crazy as Peter suggests. If I can play devil’s advocate and give one example: I’ve known many theorists (though they were always a minority) who thought that the breaking of EW symmetry had to be dynamical in nature. Now in the last 15 years, the measurements have been pointing more and more away from such an explanation but that possibility was still alive. It was one of the solutions to deal with the problems associated with a fundamental scalar i.e. you remove it from your theory. So… perhaps Nima would have been surprised but not that shocked if there was no fundamental scalar but he would be shocked if the Universe was really fine-tuned (although with split SUSY he has certainly considered such a possibility…). Anyway, I don’t think it is crazy. One slide I did not understand is the one that follows the introduction of the e+e- collider where he writes “kills all anthropic explanations”. Anybody understand what he meant there?

  3. Peter Woit says:

    Emile,

    He wasn’t saying no BSM at 100 TeV would be more shocking than no Higgs, he was saying it would be “100 times” more shocking. It’s this insistence on going over the top into wackiness that is, well, kind of shocking.

    I’m not interested enough in anthropic explanations to figure out exactly what scenario he had in mind that “kills all anthropic explanations”, but given the “100 times” claim, I’d guess that it’s yet another over-exaggeration of something.

  4. Pawl says:

    Well, implicit in Arkani-Hamed’s talk is a great truth: experiments drive physics, and at the moment theoretical work on what the fundamental questions he’s interested in is unconvincing.

    Besides the technical over-the-top comment Peter pointed to, there’s what to my mind is a more basic concern: “… we’ve attracted the best minds on the planet to work on the hardest… problems in all of Science.” Someone who says this may be (probably is) perfectly sincere, but it does raise concerns about how well he understands other fields of science or the people in them.

  5. Neil says:

    Those colorful Calabi-Yau 3D prints are great! I definitely want one. It is nice to know that string theory has finally produced something tangible.

  6. Pawl says:

    [addendum to my previous comment]

    Or, I should add, other, non-scientific, disciplines.

  7. scotty says:

    Does someone know if Arkani-Hamed also gave some advice to today’s young physicists what to work on during the next three decades of their careers, until 100 TeV data may arrive (if we are lucky)?

  8. Jon Orloff says:

    What happens if the taxpayers decide that it’s not worth building a 100 TEV collider? That could happen if there isn’t a much better reason than put forth than the airy stuff I have seen so far.

  9. george ellis says:

    Pawl is absolutely right:

    “… we’ve attracted the best minds on the planet to work on the hardest… problems in all of Science.”

    So all those people in quantum optics and nanoscience and molecular biology and neuroscience and climate change don’t compare intellectually with us. We are the elite, and their problems don’t compare with ours…..

    Do physicist really have no concept of the extraordinarily complexity of the problems neuroscientists are trying to deal with? Or the incredible achievements of the molecular biology revolution?

  10. Peter Woit says:

    My apologies to Nima, it seems that I misread and misquoted his slide (thanks to a helpful reader for pointing this out). His claim was that no BSM at 100 TeV would be 100 times more shocking than no BSM at LHC energies, NOT that it would be 100 times more shocking than no Higgs at the LHC. Read accurately, its a wild exaggeration, but not the crazy-talk of my misreading.

  11. Dan D. says:

    @george ellis,

    It seems to me that this is a fairly common (though hopefully not too widespread) attitude among scientists of *any* discipline, to view one’s own field of being of primary importance, or at least more important than those “lesser scientists” in [pick a scientific field]. It’s also true when one broadens to philosophy and mathematics, for example. You’ll see mathematicians looking down their noses at physicists for not being sufficiently mathematically rigorous, you’ll see physicists deriding philosophers for discussing problems that *gasp* may not have any answers in physics (this in particular seems to be in vogue as of late), and on the flip side you’ll see philosophers criticizing physicists for not researching the really “deep” problems. And so on. I think this is simply the tribalism of human nature manifesting itself within academia, which is no excuse, of course. It’s not necessarily a bad thing (the tribalism, that is), until it gets to the point when no effort is made to apply any intellectual rigor to understanding other “tribes”, even to the point of demonizing them (as is common for climate scientists these days, from people who should know better). Whether Arkani-Hamed’s slide in question was really betraying this sort of elitism on his part, or was simply a bit of innocent pride in his own field (nothing wrong with this), is something only he could answer, I would think.

    More on topic, as a non-particle physicist, I found Arkani-Hamed’s overall argument for a 100 TeV collider convincing enough. I think such should be built if only for the passion of needing to know “what’s over the next mountain”. I guess I’m too much of an idealist :).

  12. Dan D. says:

    Quick clarification, I meant it seems to be disturbingly common for climate scientists in particular to be demonized even by other scientists these days, which is unfortunate for the field, even if some of the individuals within it arguably deserve it from time to time.

  13. Bernhard says:

    “According to Ellis, we just need to be patient, and he has CMSSM fits preferring 2 TeV gluinos.”

    It is interesting to compare this claim with an older one (http://www.nature.com/news/2011/110228/full/471013a.html):

    “I’m wouldn’t say I’m concerned,” says John Ellis, a theorist at CERN, Europe’s particle-physics lab near Geneva, who has worked on supersymmetry for decades. He says that he will wait until the end of 2012–once more runs at high energy have been completed–before abandoning SUSY.”

    Assuming this was semi-accurate…

  14. emile says:

    Regarding the idea that the best minds are working on physics problems: this reminds me of a list by Joe Lykken on the top 10 reasons why physicists are better than biologists. One of the reasons was: Physicists used to be smarter and more arrogant than biologists, now, they are just smarter.

    Regarding the favoured regions of the CMSSM moving with time: this happens by construction. The real question is how is the goodness of fit evolving with time?

  15. Anon says:

    After the 14 TeV run with 10 times more data if LHC finds nothing fine tuning would then be at 1% level. Currently fine-tuning is probably at about a 5-10% level. If there is a natural solution to the fine-tuning problem, isn’t it much more likely that it will be found at 14 TeV run than being found only at 100 TeV? Intuitively, shouldn’t the probability of finding a natural solution to the hierarchy problem grow exponentially (or rapidly) smaller with the amount of fine-tuning?

    How can Nima make this assessment that it would be 100 times more surprising to find nothing at 100 TeV? Doesn’t sound logical to me….the 14 TeV run has not even started yet and its importance should not be undermined.

  16. P says:

    Peter,

    Nima’s ~ 100 times more surprising argument seems pretty standard. The COM energy picks up a factor of 10 compared to LHC, which then gets fed into the quadratic divergence of the cutoff.

    No need to restart the scientific argument regarding naturalness in this thread, but I think honesty requires someone pointing out that most of the community disagrees with you that this is unimportant; i.e. “Wild exaggeration” are your words, and many would disagree.

    Cheers,
    P

  17. Anon says:

    P —

    What is standard is that at 100 TeV you can establish fine-tuning to a factor of 100 more than at LHC — ie we can show that Higgs mass is 0.01% (or worse) fine-tuned compared to being 1% (or worse) fine-tuned at LHC14.

    But why would a discovery of finetuning of 0.01% be 100 times more surprising/shocking than discovery of a fine-tuning of 1%?….when the real shock is that there is fine-tuning of Higgs mass. We have a renormalizable theory that could be good all the way up to the Planck scale and it does not by itself allow us to be shocked by some artificial naturalness/finetuning standard like 0.01% (or equivalently 100 TeV machine).

    Where do you produce a small unnatural number like fine-tuning of 0.01% to set a standard for naturalness?

    Note that there are naturalness explanations based on approximate chiral symmetries for small Yukawas that could be like 0.1, 0.01, 0.001, 0.0001 and even 10^-5 in the standard model. Similar chiral symmetries and arguments are at work in SUSY theories to protect the Higgs/Higgsino masses. And LHC would show beyond any doubt show that such a naturalness argument has failed in the case of the Higgs and hierarchy problem.

  18. Peter Woit says:

    P,
    Others have weighed in, but the obvious point is that making degree of shockingness linear in the degree of fine-tuning, instead of, say, logarithmic, is, well, the kind of thing you would do if you like exaggeration.

    In general, I think if you have a hypothesis that something should be order 1, and experiment bounds it at .01, it’s more conventional to start questioning your hypothesis than to announce that a bound of .0001 would be 100 times more shocking.

  19. The Vlad says:

    Peter:

    Do you understand what Craig meant by the second part of the quote “there are many valid reasons to favor supersymmetry, some of which are only strengthened by what we’ve learned so far at the LHC”?

    Do you think he was alluding, as he later writes, to the claim that “[SUSY] predicts the Higgs mass to lie below 135 GeV, in good agreement with observation”?

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