LHC results put supersymmetry theory ‘on the spot’

The HEP theory community is atwitter over a BBC News story LHC results put supersymmetry theory ‘on the spot’ that reports from the Lepton-Photon 2011 conference in Mumbai, where more null results relevant to supersymmetry were reported. According to the story:

Results from the Large Hadron Collider (LHC) have all but killed the simplest version of an enticing theory of sub-atomic physics.

Researchers failed to find evidence of so-called “supersymmetric” particles, which many physicists had hoped would plug holes in the current theory.

Theorists working in the field have told BBC News that they may have to come up with a completely new idea.

Joe Lykken, an organizer of the SUSY11 conference about to start at Fermilab, is getting worried:

“There’s a certain amount of worry that’s creeping into our discussions,” he told BBC News.

The worry is that the basic idea of supersymmetry might be wrong.

“It’s a beautiful idea. It explains dark matter, it explains the Higgs boson, it explains some aspects of cosmology; but that doesn’t mean it’s right.

“It could be that this whole framework has some fundamental flaws and we have to start over again and figure out a new direction,” he said.

On Twitter, there’s Carlo Rovelli gloating here, Matt Strassler (here and here) and Lisa Randall (here) claiming all is not lost. In an exchange here, Strassler notes that he’s fighting to prevent the risk of “no money for your research”. It’s unclear if he’s referring to funding for the LHC experiments or for SUSY theory. There is a real long-term danger to HEP experimental funding once the public realizes that they’re not getting the extra dimensions some have promised them, but the time to fight that risk was the many years during which hype about the LHC was rampant.

Both Strassler and Kane now seem to attach great importance to the point that, in some SUSY variants, gluino mass bounds are lower than the 1 TeV of the most popular models, more like 500 GeV. Kane goes so far as to claim that the gluino will be found, at masses below 1 TeV:

The current limit on gluino masses is not above 500 GeV. Whether the squarks are indeed so heavy is not the issue, the point is that if they are the limits on gluino masses are smaller than is often stated. I and others expect this decay to tops and bottoms is the signature by which gluinos will be found, with masses well below a TeV.

Presumably LHC searches are underway for signatures of gluinos in this mass range in these versions of SUSY. I’d be very curious to hear what the status of those searches is. If they come up negative, will SUSY proponents finally give up? New results relevant to SUSY are appearing rapidly, see the latest from CMS here and here.

For some historical perspective, something I ran across recently was a 1993 New York Times report 315 Physicists Report Failure In Search for Supersymmetry, which described null results from early days of the Tevatron. One very funny thing about the article is that much of its emphasis was on the unwieldy nature of the CDF detector, with its $65 million budget and huge number of 315 physicists.

Update: SUSY11 opens tomorrow with a talk by Murayama that incorporates the BBC News story and describes evidence against superpartners as “impressive, worrisome, but not quite there yet”. No indication of when it will get there. The title of the talk: Why do SUSY in 2011?

Update: Quite interesting reading is Michael Peskin’s summary talk at Lepton Photon. On the topic of this posting, he writes:

Before the start of LHC, I expected early discovery of supersymmetry in the jets+MET signature. Many other theorists also had this belief. But, it was not correct.

and he explains why this was (large amount of fine-tuning required if superpartner masses are even as large as 1 TeV). He also explains possible ways to construct SUSY models that evade current experimental bounds while keeping superpartner masses relevant to the fine-tuning problem from getting much too large.

This week at CERN there’s a workshop on Implications of LHC results for TeV-scale physics, which should have many interesting talks.

Update: Yet another technical talk about the state of SUSY searches that begins by reproducing the BBC story is today’s talk at CERN by John Ellis. Ellis gives an overview of SUSY fits. The regions identified by these (pre-LHC) as the most likely place for SUSY to show up have in many cases now been ruled out. With the latest LHC data, the “most likely” region moves out to higher and higher masses, with less and less of a good fit. Ellis concludes:

LHC data putting pressure on popular models.

Update: Another review of the SUSY situation is here (from the Physics in Collision conference). A quote from Altarelli:

It is not time to desperate yet… but maybe it is time for depression already.”

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70 Responses to LHC results put supersymmetry theory ‘on the spot’

  1. Giotis says:

    Why on earth Rovelli is gloating and why these results are good news for LQG? Did LQG make a prediction about SUSY at LHC that I’m not aware of? LQG has nothing to say about SUSY, for or against (especially about SUSY at LHC).

    It’s really a pity; I thought Rovelli was a modest guy and a serious scientist but he jumped at the opportunity to mislead the public and his pet theory for no good reason.

  2. Giotis says:

    “and his pet theory for no good reason.”

    It should be:

    “and to hype his pet theory for no good reason.”

  3. Maury Markowitz says:

    ““It’s a beautiful idea. It explains dark matter, it explains the Higgs boson, it explains some aspects of cosmology; but that doesn’t mean it’s right.”

    Forgive this comment from the laity, but as I understood it, nothing in this quote is, at first glance, correct. That being the case, I’m wondering if someone can help point me in the right direction for further reading, as I assume the problem is mine.

    1) “It explains dark matter”: I was under the impression that it was *possible* that one of the super partners might have the right mass and properties to serve as a WIMP suitable for DM. I have not heard of anything more direct that that, however, along the lines of “with supersymmetry, DM is not an issue in the first place”, or, less difficult, “in order to work, susy must have a [insert super partner here] with mass of xx TeV that would exactly explain DM”.

    2) “it explains the Higgs boson”: I assume he is referring to the problems with the hierarchy problem of Higgs mass. If that is what he’s talking about, I was under the impression that susy simply moved the goalposts on this problem, as it does not explain the μ problem. But is this what he is saying?

    3) “it explains some aspects of cosmology”: well so does practically everything – notably the DM that was already mentioned. This is definitely something I am weak on, what does susy talk about in cosmology that isn’t part of DM?

  4. Bernhard says:

    That BBC article was not so good, but the journalist was probably only passing on what he was being told, there´s no way for him to judge how the LHCb results affect SUSY. Besides, people can´t complain about a little bit of hype against SUSY since in the pre-LHC era some people abused from it in the other direction.

    I agree with those who say that SUSY is not ruled out and that is rather premature to make those claims. However, there is no way the LHC or even the super LHC could rule out the complete SUSY parameter space, which means that arguments such as “the strategy to find SUSY at the LHC rest upon assumptions” can go on forever.

    What we should be checking is how the LHC results are messing up with SUSY motivations. I´m sure right now it´s easy to evade experimental limits in terms of affecting the SUSY “solution” to the hierarchy problem, but would it be after 2012? After, 5 10 years of LHC running?

  5. anonymous says:

    “There is a real long-term danger to HEP experimental funding once the public realizes that they’re not getting the extra dimensions some have promised them, but the time to fight that risk was the many years during which hype about the LHC was rampant”

    Some of us have been saying this for a long time – it’s a bad coincidence (or maybe fate) that the current government funding crisis is happening at the same time that many of our theories (which have been made popular through broadcast science channels) are being proven only to be fantasies. Biology is starting to look pretty interesting …

  6. Peter Woit says:


    I also thought this was fairly outrageous hype. Your explanations of 1 and 2 I think are correct, and I also have no idea what he was referring to about SUSY explaining cosmology.


    The LHCb results are relevant, although they’re just one more example of this problem for SUSY of it not showing up in precision electroweak measurements. Matt Reece, in his recent KITP talk, claims that these are actually a more serious problem for SUSY than not finding superpartners at the LHC. If you had seen 1 TeV squarks or gluinos at the LHC, it would be very hard to understand why they didn’t contribute measurably to cause deviations from SM predictions in the electroweak sector.

    It has become increasingly difficult to come up with a plausible explanation for why experiments that should be sensitive to SUSY see nothing. With the missing superpartners at the LHC, and the new LHCb result, this may have reached the tipping point, where even long-time SUSY proponents like Joe Lykken are getting ready to throw in the towel.

  7. Emile says:

    Anonymous: before you enroll in biology courses, you should wait to see if a Higgs is found and if anything else shows up. Will there be a Higgs and nothing else? Too soon to bail out… (besides, have you ever seen Joe Lykken top ten list of why physicists are better than biologists?)

  8. Shantanu says:

    Maury, I agree you should take all such claims with a grain of salt.
    in 1998, P. Ramond claimed that the Super-K results for non-0 neutrino mass point evidence for low-energy supersymmetry.

  9. anonomous says:

    Emile: Just saw the list and liked #3:

    Particle Physics promises:
    – superstrings, supersymmetry, supercolliders.
    Biology promises:
    – supermice, supertomatoes.

    I guess we will have to settle for the big tomatoes!! What will string theorists do with their free time?

  10. Roger says:

    A 2006 NY Times article said, “Physicists are a bit frustrated that their results keep agreeing with the Standard Model and so far show no hint of supersymmetry.”

  11. Maynard Handley says:

    “impressive, worrisome, but not quite there yet”
    “There’s a certain amount of worry that’s creeping into our discussions,”

    Am I the only one extremely irritated by this language? “What do you mean, WE, white man”.

    The discomfort these people are feeling seems fully justified by the fact that they have no qualms about speaking for the whole of physics.
    Perhaps they’d be mocked a little less by other physicists if they used phrases like “this is worrying for OUR theory” in their statements? Until they learn that level of humility, personally I say to Carlo Rovelli et al “good work and keep at it”.

  12. Matt Reece says:

    I’m going to violate my personal rule against writing blog comments that can be easily found by Googling my name, because I want to take issue with this:

    Matt Reece, in his recent KITP talk, claims that these are actually a more serious problem for SUSY than not finding superpartners at the LHC. If you had seen 1 TeV squarks or gluinos at the LHC, it would be very hard to understand why they didn’t contribute measurably to cause deviations from SM predictions in the electroweak sector.

    Rather, what I said in my KITP talk is that flavor is still the strongest constraint that we worry about when we think about SUSY models. I don’t agree that precision electroweak physics is a strong constraint on supersymmetry. Flavor is a strong constraint on any physics beyond the Standard Model: check out Table 1 of this paper by Isidori, Nir, and Perez to see just how bad. Because the bloggy audience might not know about this aspect of high-energy physics, I’ll briefly summarize. If we add generic higher-dimension operators to the Standard Model, we find that some of them associated with flavor-changing neutral currents are suppressed by a scale of 10,000 TeV (or even more if we allow them to violate CP). This means that if we had new particles that couple strongly and in a completely generic way to the Standard Model, they have to be heavier than 10,000 TeV, way beyond the reach of the LHC. The constraints in sensible models are not this bad, because the new physics isn’t completely generic: it couples weakly and often at least approximately respects the Standard Model’s flavor structure, both of which make the constraint more mild. But compared to precision electroweak, it’s a much bigger worry, and absolutely any model of new physics near the TeV scale has, as a zero-order task, to explain how it avoids causing problems with these constraints.

    So how bad is this for SUSY? It’s not necessarily bad at all. One well-motivated way of breaking SUSY in the Standard Model, gauge mediation, has a special structure that’s automatically free of flavor problems. (However, it has some cosmological problems, especially if you try to embed it in a more UV-complete framework, which were second on my list of things to worry about but far beyond the scope of this comment box.) Other approaches to SUSY breaking are somewhat more susceptible to flavor problems, but are also less well-understood, depending more on high-scale physics. I gave a brief, but I think reasonably complete, list of such scenarios in the KITP talk (and Yael Shadmi pointed out that other models with somewhat more interesting possible flavor signals are still allowed). So if we see squarks, I agree that we will need “to understand why they didn’t contribute measurably to cause deviations from SM predictions,” but in the flavor sector, not in the electroweak sector — and the answer might turn out to be a mechanism we already understand, like gauge mediation.

    Precision electroweak really doesn’t bother me at all for SUSY. It’s a somewhat more serious problem for technicolor (or Randall-Sundrum), which as far as we know always has dangerous contributions to electroweak observables, but a mild tuning can get around it, so we could just be unlucky that nature didn’t give us that hint. Flavor is the biggest constraint on technicolor/RS, just as much as on SUSY, if not more so (indeed, the most serious attempt I know to really confront flavor in technicolor is probably Markus Luty’s work on using SUSY to solve the problems!).

    Anyway, let’s be patient and wait for more data and more thorough analysis of existing data. The LHC is doing amazing things, but so far we’re only seeing the first-pass results coming out. A lot more is on the way, and I for one hope for surprises….

  13. Jeff says:

    Matt Strassler describes in more detail his position on funding concerns, as written on the comments section of his webpage (http://profmattstrassler.com/2011/08/19/current-lhc-data-and-supersymmetry-is-supersymmetry-in-trouble).

    He says:
    “… a 9 billion dollar experimental facility’s long-term future [is] on the line. There are consequences to making incorrect or overoptimistic statements to the press. In my view, we need to be quite precise about what we say; the public, and the politicians that provide the money, want to know what is going on, and we will pay a price if we say one thing and then have to backtrack. And if we disagree with each other, that’s fine; it is best that the public and politicians know that there is no scientific consensus yet.”

  14. DB says:

    Human nature being what it is, I expect experimentalists and SUSY advocates to come closer together and not engage in the dogfights that Strassler fears. Why?, well, there is only one positive outcome on the cards and it plays to the interests of both camps: a discovery of a “low” energy Higgs in the 115-128Gev range. No Higgs and a simple confirmation of the standard model would be a disaster for both camps: the premature shutdown of the LHC and all that that would entail.
    A low energy Higgs discovery – the only one still just about on the cards – keeps SUSY alive as the search strategies are changed to hunt for every conceivable variation in the 100+ parameter SUSY universe, and so stretch out the life of the LHC.
    Bad news for those who would hate to see experimental physics go down the road of hype and false promise, but hey, folks gotta eat. And the alternative looks like no machine at all.
    But lurking always in the background is the data from precision electroweak data which points to a Higgs of c.72 Gev, already ruled out by LEP2. One could argue with some justification that the LHC was built on the basis of a solid dose of hype all of its own. Tick tock, tick tock.

  15. Peter Woit says:


    Many thanks for the helpful explanations about this.

  16. Maury Markowitz says:


    “And the alternative looks like no machine at all.”

    That’s true, but the “no machine” case was either going to happen at LHC or the one after it. SSC’s cancellation wasn’t entirely surprising in that respect, and that LHC is alive is a testimonial to the very interesting funding system CERN’s arranged (took notes from NASA it seems 🙂

    Looking to the future, I suspect that this is the last new high-end accelerator I’m likely to live to see. There’s nothing particularly interesting beyond LHC except “bad” higgs, and I suspect that funding for such a machine is unlikely to be forthcoming.

    But on that note, I don’t think I’ll live to see man on Mars either, so maybe I’m just a spoilsport. And who knows, someone might get a surfatron working!


    Darn, I was hoping I simply didn’t understand the issues well enough. I’m always looking for an excuse to pick up a new read.

  17. Bobito the Payaso says:

    Perhaps soon deans will count twitters when deciding on promotion.

  18. AlBme says:

    I can see how some researchers might be concerned over future funding over an idea that may very well fail to produce empirical evidence. On the other hand, it’s an opportunity for new ideas to be considered and seriously examined. These scientists shouldn’t need to be reminded that even a negative experimental result advances our knowledge of nature. The LHC is producing more data probably than any other experiment preceding it. If they bother to look, I’ll bet they’ll find plenty that isn’t explained completely by even the Standard Model. From that, new ideas can be proposed and examined.

  19. Bernhard says:

    I can´t access Peskin´s talk. I´m trying it for days already but just loads forever and nothing.

  20. Peter Woit says:


    The talk is there, it’s about 6.5 MB, although downloading and opening in my firefox browser was slow and sometimes flaky. One might want to try a different browser…

  21. Jack Levitt says:

    Let’s wait to hear what Witten has to say before we panic, okay?

  22. anon says:

    I can’t help but feel that SUSY is in a deeply oversold condition at the moment. I’d be tempted to buy shares in anticipation of a short-term snapback rally in the fall.

  23. null says:

    Would not finding a Higgs rule out SUSY?

  24. Peter Woit says:


    No. SUSY also has a Higgs, actually at least two of them. One question everyone will be asking once a Higgs is found is whether it is a SM Higgs or a SUSY Higgs.

  25. Marcus says:

    Giotis’ first comment (with the snide omitted):
    “why these results are good news for LQG? Did LQG make a prediction about SUSY at LHC that I’m not aware of? ”

    Yes and you are evidently not aware of it. Finding signs of SUSY would be a considerable setback for the Loop researchers. It would make it incumbent on them to incorporate SUGRA which would mean back to the drawing board for some.

    The current LQG does not do supergravity. This was pointed out by Thomas Thiemann at the recent loops conference in May, where he presented a seminal paper on how to formulate LQSG. He discussed the problems to be overcome. (Also with extra dimensions.) The motivation he gave was basically to have “insurance”. Suppose the LHC detects signs of supergravity and or extra dimensions, just in case let’s see how the theory could adapt.

    One would presumably have to abandon the results of the past few years–I’m guessing it might amount to going back to how things were around 2005 or 2006.

    Thiemann and two of his PhD students have come out with several papers on this subject in the past 3 or 4 months.

    So from a practical standpoint it is certainly good not to see SUSY and this is a simple observation, not “gloating”, which any one familiar with the situation can make.

    Here are 3 papers if you want to read up:
    1. arXiv:1106.1103 [pdf, ps, other]
    Towards Loop Quantum Supergravity (LQSG)
    Norbert Bodendorfer, Thomas Thiemann, Andreas Thurn
    Comments: 12 pages
    Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics – Theory (hep-th); Mathematical Physics (math-ph)
    2. arXiv:1105.3710 [pdf, ps, other]
    Towards Loop Quantum Supergravity (LQSG) II. p-Form Sector
    Norbert Bodendorfer, Thomas Thiemann, Andreas Thurn
    Comments: 12 pages
    Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics – Theory (hep-th); Mathematical Physics (math-ph)
    3. arXiv:1105.3709 [pdf, ps, other]
    Towards Loop Quantum Supergravity (LQSG) I. Rarita-Schwinger Sector
    Norbert Bodendorfer, Thomas Thiemann, Andreas Thurn
    Comments: 43 pages
    Subjects: General Relativ…

  26. Chris Austin says:

    Matt Reece, thanks for the clarifications. Could you comment on Lunghi and Soni‘s claim that “the CKM-paradigm now appears to be in serious conflict with the data”?

  27. Shantanu says:

    So Marcus, how then does LQG address the dark matter problem? or is the dark matter have nothing to do with electroweak scale according to LQG?

  28. Giotis says:


    It is widely accepted that LQG is not incompatible with SUSY/SUGRA and the papers you mentioned just prove this point. This is the reason why no one in this field ever said that finding SUSY at LHC would mean that LQG is wrong.

    No, Rovelli is not gloating due to these technical implications you mentioned. He is gloating because he believes that not finding SUSY at LHC will be a blow for String theory at least at psychological level and LQG (as a rival) will benefit from that.

    LQG has nothing to say about physics at LHC; it can’t even derive GR at the classical limit.

  29. Peter Woit says:


    Please, enough LQG/string warfare, this really isn’t very relevant to the topic of SUSY.

  30. Marcus says:

    Shantanu and Giotis,
    My reply to your recent comments addressed to me is here:
    I responded in some detail. You are cordially invited to continue discussion there, if you wish.

  31. null says:


    No. SUSY also has a Higgs, actually at least two of them. One question everyone will be asking once a Higgs is found is whether it is a SM Higgs or a SUSY Higgs.

    PW, to clarify, my question was what would be the ramifications to SUSY and SUSY extensions of the SM like MSSM if future LHC results rule out Higgs in the 115-145 range? So instead of finding 1 as predicted in SM or 2 as predicted in MSSM, LHC rules out the Higgs.

  32. Peter Woit says:


    The main thing the LHC is looking for is a SM Higgs, with only one unknown parameter. If that is ruled out, it will mean only that that specific theory is ruled out. SUSY extensions of the SM contain something like a SM Higgs, as well as other Higgs fields. There are more parameters, so completely ruling out SUSY Higgs fields is trickier, but they need to have something that plays the role of the SM Higgs, so you should be able to see that.

    This still wouldn’t rule out the general idea of SUSY though, just SUSY extensions of the SM (ruling out Higgs, you’ve ruled out the SM). Whatever replaces the Higgs field and causes electroweak symmetry breaking, you can imagine a SUSY extension of that new theory existing. So, no, ruling out the Higgs does not rule out SUSY in general.

  33. null says:

    You answered my question thanks.

  34. Shantanu says:

    Peter, another article in New scientist

  35. Bernhard says:

    Here is an article on a perhaps not most reliable magazine for scientific matters, but anyway, it´s interesting to see the SUSY hype is now going “counter stringwise”:


  36. Peter Woit says:

    Thanks Bernhard. The comment section of that article is priceless…

  37. SpearMarktheSecond says:

    Perhaps the most impressive thing is we aren’t replaying the mid-1980’s, when UA1 (mostly) and UA2 (a little) had false SUSY signals for a while, which were really background. CMS and ATLAS are way better run with better background estimates.

    The flavor sector constraints on SUSY have long been quite strong… Haim Harari among others long emphasized this point. But contemporary SUSY models all were engineered to evade the constraints from the lighter flavors, although the Bs results keep squeezing the parameter space more.

    In the early 1990s all the greats testified to Congress that LHC at 14 TeV couldn’t make a discovery if the Higgs got heavy… therefore the SSC with 40 TeV in the center of mass was mandatory. Although we’ve had an interregnum where the Higgs has been light, with good justification, maybe the multiple blurry pictures from loops of the Higgs were over-interpreted. And so the SSC scenario might be coming true.

    For sure the SUSY and extra dimensions stuff was oversold. But when Columbus argued for his ships, he portrayed the riches of Asia, which he never actually obtained. So the real point is the machine builders at CERN and in the old days at the SSC CDG knew they were shooting for the highest energies possible for pure exploration. Mel Schwartz was so clear in his testimonies on this point. The outer circles of HEP experimentalists and theorists pitch SUSY and extra dimensions.

    Perhaps the deeper point is… if nothing knew is seen at the LHC, even no Higgs, what next? Give up? Or build the next hadron collider in…. China? In Texas under President Perry? But a linear collider doesn’t seem wise.

  38. Peter Woit says:


    I’m also surprised that we haven’t had some mistaken “discoveries” of supersymmetry so far.

    Sometime soon I should write about the question of the “next collider”. I don’t think extra dimensions and supersymmetry can be used to sell it if they don’t show up at the LHC. Unless the LHC comes up with something that falsifies the SM, the case for a new machine is going to be difficult. Best bet I think is no Higgs, but some alternative origin of electroweak symmetry breaking. The argument has always been that the LHC is a “no-lose proposition”, either it finds the Higgs or has to find something else. We’re going to find out if that argument was right…

    In practical terms, the most viable higher energy “next collider” seems to be a revamped LHC with higher field magnets, more than doubling the energy. But even for that, the case won’t be easy to make unless the LHC gives some reason to believe that there’s something to be seen at 33 TeV that can’t be seen at 14 TeV. Maybe that old testimony needs to be dusted off…

  39. SpearMarktheSecond says:

    I think the old argument was that W’s and Z’s become strongly interacting under a very heavy Higgs… so you start getting W-W- hard scattering, and jets of W’s and Z’s like we now have jets of quarks and gluons. The weak become strong.

    Good enough to justify $30 billion or something like that in today’s dollars? Don’t know.

    Maybe an LHC upgrade is the only way to go. We’ve seen how hard even getting to 7 TeV in the center of mass is. But last time I checked, Europe had some money problems too. Maybe China and India can become full member states at CERN…

  40. Lee Brown Jr. says:

    The argument has always been that the LHC is a “no-lose proposition”, either it finds the Higgs or has to find something else.

    Maybe it’s a bit premature, but you addressed precisely what I was wondering, “Is it possible for the LHC to find nothing?” How would physics move forward?

  41. Bernhard says:

    Lee Brown Jr.,

    Of course this is possible, although many of us hope it won´t happen, me included.

    Other fields of physics will move forward for sure, just not sure how particle physics would without new experimental evidence. Would be near to impossible to justify building another billion dollar accelerator, so in my opinion the only hope in this scenario would be to wait for technological advance to a point that to create TeV collisions you don´t need a 27 km accelerator and expensive magnets. And this possibility is in a really distant future.

  42. SpearMarktheSecond says:

    I think the advocates of the SSC circa 1990 most definitely argued that the LHC could find nothing. That’s how the justified 40 TeV in the center of mass for the SSC… by saying that energy was necessary to confidently project observation of the new physics deemed necessary if no Higgs (or SUSY) were detected.

    As far as I remember, that physics is, at high momentum transfer, W’s and Z’s behaving as though they had effectively strong interactions, due to new effective terms in the lagrangian necessary to forestall infinities.

    Back in 1990 there was a fair amount of skepticism about achieving the luminosities now actually achieved at the LHC. Center of mass energy seemed like the bet more reliable than luminosity. So unless the Higgs pops out between 115 GeV and 145 GeV, a lot of scrutiny of the LHC’s ability to see high Q^2 W/Z scattering will happen… likely interesting info is already buried in all the studies.

    Maybe the achieved high luminosities prove the early 1990’s arguments wrong.

    If no Higgs, too hard to tell if LHC will be the high water mark of HEP, like the Apollo program was for NASA. Could be, but there are huge differences…

  43. HoldYourHorses says:

    Guys, the LHC was designed to run for *decades*, and after one year with no superpartners everyone is losing their minds. I get the impression people are thinking “so the LHC had its shot, found nothing, so what’s next”. This is nonsense.

    People used to think in the 80s the top quark would be found at 30 GeV, then it was “always around the corner” until it was discovered at 175 GeV in the nineties. The moral is that we (and I speak as a theorist) are actually quite bad at predicting what nature will do.

  44. Model and Sim says:

    I think the what happened to SSC will go down as one of the great tragedies of our era. Its still too early to tell with LHC, but I agree with Peter that if we don’t see something it will be very difficult to go to the next level. The margins simply are not there to justify such a large expenditure. High energy searches in space might be the only option in the near future.

  45. younghun park says:

    It is possible to think the next collider without finding something valuable at LHC
    in the case of no money problem in Europe and USA. Now, Europe and USA have big money problem. Other people won’t agree to bulid the expensive collider.
    So, our friends in CERN have to find higgs or something else.

  46. Peter Woit says:

    HYH, Model and Sim,

    There are two distinct issues here. The first is supersymmetric extensions of the standard model, which never had much to recommend them. Here the on-going piling up of negative evidence is finally causing believers to rethink, and that process will just continue for the next few years. To the extent that these were used as a big selling point for the LHC, that was a decision bound to incur some future cost, we’ll see how large. Even more so for extra dimensional models, which virtually no one takes seriously. Using these as part of the LHC sales pitch was guaranteed to cost something in credibility later.

    The real issue is the Higgs, and there the time-frame for something interesting happening is months not years, with evidence for or against a SM Higgs likely to start showing up soon, although the current situation is highly ambiguous. If there is a Higgs, the sales job for a new machine is going to be about the importance of being able to study the thing, with a serious problem the argument that “the SM Higgs theory seems to work, why spend lots of money checking it?” If there is no SM Higgs, there’s going to need to be a serious effort to explain to the public why this is a major discovery, opening up whole new areas of research. There will undoubtedly be a lot of analysis of issues like the W/Z scattering one explained by SpearMarktheSecond. Unfortunately, absent the kind of breakthrough mentioned by Bernhard, viable options for making progress are limited (in particular, going into space doesn’t help). Increasing the LHC energy with new magnets looks like something that could address the physics issues, at tolerable cost.

    Anyway, I’m guessing that by next year it will be clear which way this is going to go with respect to the Higgs.

  47. null says:

    “The real issue is the Higgs, and there the time-frame for something interesting happening is months not years, with evidence for or against a SM Higgs likely to start showing up soon, although the current situation is highly ambiguous. ”

    do you have any idea how soon the Higgs issue will be decided at current rate of data accumulation?
    It’s my understanding the recently published exclusion of 145 gev and above was based on an accumulated 2 fb-1 data set? 95% confidence

    Is 95% exclusion really a strong exclusion? I am aware that “discovery” is 5-sigma, so exclusion is a lower 2-sigma?

    1-how many fb-1 per month is being collected and analyzed by LHC
    2- how many fb-1 to find evidence or rule out Higgs in the 115-145 range? 95%

    Is a 95% exclusion of Higgs in 115-145GEV acceptable to researchers to give up on the Higgs or is it more stringent? If excess events are reported at 3-sigma at 115GEV, this would be reported as a possible Higgs discovery?

  48. Peter Woit says:


    The LHC will run with protons until the end of October. Estimates are that they’ll accumulate 5 inverse femtobarns in each experiment. Latest public release of data was based on 1-2 inverse femtobarns (and no combination of data from the two experiments). There are old projections made last year about how much data it would take to exclude at 95% level all the way down to the LEP limit, I believe it was about 5 inverse femtobarns or so.

    Yes, typical standards for exclusion are different than for a discovery claim. If the Higgs isn’t there, there seems to be a good chance of having a 95% exclusion result, possibly using both experiment’s data. If it is there, the 5 sigma standard may not get met, but a 3-4 sigma signal would start making people think something was there.

    Anyway, we’ll see what the data says, sooner or later….

  49. null says:

    you answered my question. What happens after October? Do they shut down or switch to heavy nuclei, or retool for 4TEV (8 TEV total)?

    Does combining the data from both channel change results?

    How soon after they collect 5 fb-1 will they report their finding?

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