No WIMPs

A commenter points to the long-awaited release of a preprint from the XENON100 experiment giving results from a 100-day run last year. This is the most sensitive dark matter experiment that has released data. The result: with an expected background of 1.8 +/- .6 events, they see 3 events (i.e. about what you’d expect if there’s nothing there). For a WIMP mass of 50 GeV, this allows them to exclude certain WIMP cross-sections at the level of 7.0 x 10-45cm2. This pretty conclusively kills off some other claims by dark matter experiments to have seen something, especially the CDMS result from late 2009 (see here).

One motivation for supersymmetry has always been that it can provide a WIMP with the right properties to explain astrophysical dark matter observations. This new data rules out some (if you use the SUSY expectations plotted in the new paper), or most (if you use the expectations plotted in the CDMS paper, see here and here) of the possible parameter space where such a particle is expected, providing yet another nail in the SUSY coffin.

Update: More details available at Resonaances and Tommaso Dorigo’s blog.

Update: For a detailed analysis of the implications of the XENON100 result for supersymmetry models, see here.

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106 Responses to No WIMPs

  1. Shantanu says:

    Peter, I know several people (including my former colleagues) who still
    believe proton decay exists and continue to do thesis projects and searches for it, despite 30 years of null results. So don’t expect people to stop believing in supersymmetry for weak-scale interaction strength based dark matter even if LHC or NLC finds nothing.

  2. Peter Woit says:

    NBH,

    This is about the LHC. Sure, there’s a black hole in the center of the galaxy, but none are going to be made in Geneva.

    milkshake,

    It’s possible to come up with scenarios where there would be new physics missed by the LHC because of the detector triggers. I have no idea how to assign a probability to this. If the experimentalists are doing their job well, it should be low.

    Shantanu,

    I think people should keep searching, both for WIMPs and for proton decay, as long as they are able to keep increasing the sensitivity of these experiments. Doesn’t really matter if the main motivation is misguided, you still should look where you’ve never looked before to see if something unexpected turns up.

    By the way, I haven’t followed that story recently, but last I heard, proton decay experiments were getting to the point where they too could start putting nails in the SUSY coffin…

  3. D R Lunsford says:

    Hey, UCLA is being positive

    http://newsroom.ucla.edu/portal/ucla/dark-matter-search-one-step-closer-200546.aspx

    “Now that we know there are no unicorns in Chicago, we are that much closer to finding them.”

    -drl

  4. Susy WIMP says:

    I’ve heard an interesting take on this. Since we are looking for dark matter interacting via Higgs exchange, could it be that the result is evidence against a single scaler Higgs, rather than against supersymmetry?
    Does anyone know the status of Xenon-1t, XMass etc.? Are we expecting another order of magnitude increase in sensitivity within the next one or two years?

  5. M. Wang says:

    Tommaso,

    “we are Bayesians by nature, at least somewhere close to our amygdala. And if the prior belief in SUSY was what it was four years ago, we have to acknowledge that it has shrunk quite sizably now.”
    This is the best comment from a physicist that I have read in years, and how relevant it is here! I wish more scientists could have the broad knowledge and common sense you demonstrated in one sentence. It is sad to see so many confusing narrow technical expertise with true understanding of a subject.

    Mike,

    “I would judge the current disorder as a good sign — for surely it is now just a matter of time (short I would hope) until a better fundamental explanation emerges.”

    I cannot share your sanguinity. In 30 years of wild goose chase, the majority of the institutions studying theoretical particle physics have been staffed mostly with worshipers of the false faith. Here I don’t mean false theories but an entire system of anti-scientific attitude. Witness the total inability for someone like Holycow to appreciate the relevance of the failure of their previous predictions. People don’t accept failure easily, particularly not when they are in their 40’s or 50’s and had their entire careers built on not just the failed ideas but also the false methodology. On top of this, they are many. Tommaso may be able to point out more specific research regarding how crowd psychology induces greater variations from rational behaviors.

    Take the investment banking industry for example. For years, they spouted all kinds of theories that purported to show their great contributions to the efficient markets and therefore to the economy as the justification for looting the nation’s wealth. The great recession proved them false, but have they stopped doing what they were doing? Once the regulators chose rescue over closure, their jobs were secure and they promptly went back to the old business of ripping off the nation. When the senate questioned Goldman Sachs regarding its behavior, the CEO simply lied and got away with it, even though now some senators publicly acknowledge that they have been lied to. The moral is, if you don’t clean out the scums, don’t expect them to behave differently if given a second chance just because they had created a big mess the first time around. Last time I check, most of the physics institutions still follow the tenure system…

  6. Thomas Larsson says:

    So crackpots don’t care about the experimental verdict. What else is new?

  7. chris says:

    Mike,

    if no Higgs is found below say 150GeV SUSY will start drifting into the fringe science direction and slowly die off similar to -say -the steady state model in the ’70s and ’80s.

  8. Holycow says:

    “if no Higgs is found below say 150GeV SUSY will start drifting into the fringe science direction and slowly die off similar to -say -the steady state model in the ’70s and ’80s.” Wrong. A light Higgs is a prediction of the minimal versions of SUSY.

  9. Holycow says:

    M. Wang

    “This is the best comment from a physicist that I have read in years”. You have to read more.

    “Witness the total inability for someone like Holycow to appreciate the relevance of the failure of their previous predictions.” What is astonishing is the inability of some to understand the very basic fact that in the road to discovery your limits will be pushed up and chunks of parameter space will be discarded. How on earth can it be otherwise? I have no problem at all in giving up on a theory if it doesn’t have anything to do with nature. (By the way, I’m not like Georgi who once wrote a paper titled “Why I would be sad if a Higgs boson is found”.)
    But I will not give up until it has been put in a hole by experiment, which is not the case for SUSY. (Not even close). If you think otherwise, that’s your problem, but respect the work of others who still have to collect much more luminosity searching for this jewel.

    You would have given up in the search for the top when the lower limit was at 90 GeV. (Don’t reply saying this case it’s not the same, because we knew it had to be there. I know. What I critize is the attitude of people putting down others worthier than them simply because they fail to understand the issues involved or because of their personal prejudices).

  10. ShrugOffNaysayers says:

    It seems that everyone here would get very happy if nothing is found. That’s the difference to actual scientists.

  11. Rhys says:

    The WIMP miracle is a remarkable theoretical fact which now looks less and less likely to be the way nature actually works. This is completely logically independent of supersymmetry, but some SUSY models naturally provide stable WIMPs. So this is really only evidence against certain realisations of supersymmetry; there is plenty of scope for gravitino or axion dark matter, for example. (I have personally written exactly one paper about low-scale SUSY, and our model doesn’t have stable WIMPs).

    I agree with chris that the absence of a light Higgs would be much stronger evidence against SUSY. Of course, by the time a light Higgs can be ruled out, we should have found some superpartners anyway! If we haven’t, I will probably already have given up on weak-scale SUSY.

    Susy WIMP:
    Somebody may correct me, but I don’t believe the direct detection experiments have yet begun probing Higgs-exchange cross-sections.

    imho:
    In my opinion, ‘realistic’ technicolour models are a lot uglier than low-scale SUSY models (which are themselves rather messy).

  12. chris says:

    holycow asys:

    “if no Higgs is found below say 150GeV SUSY will start drifting into the fringe science direction and slowly die off similar to -say -the steady state model in the ’70s and ’80s.” Wrong. A light Higgs is a prediction of the minimal versions of SUSY.

    that was exactly my point ^_^

  13. Holycow says:

    Chris, it’s important to give the right message. If you say SUSY *predicts* a Higgs below 150 GeV you are misleading people. That prediction is not universal and can be violated. SUSY does predict superpartners and that’s the key search, not the Higgs.

    Rhys, thanks for your post. It’s good to read reasonable people from time to time.

  14. Thomas Larsson says:

    Speaking about nails, how are the searches for permanent electric dipole moment going? In 2005, Chad Orzel wrote: “Experiments currently in production should lower that limit by another 2-4 orders of magnitude, which would either find a non-zero EDM, or rule out pretty much every theory now on the books. I’m told that the theorists who deal with this stuff are starting to sweat a little… ”

    But I guess the silence speaks for itself…

  15. chris says:

    “If you say SUSY *predicts* a Higgs below 150 GeV you are misleading people.”

    sure you would, i fully agree with you. it would be equally misleading as e.g. saying that SUSY is a fact of nature.

  16. Holycow says:

    “It would be equally misleading as e.g. saying that SUSY is a fact of nature.” Not really. This might be true (we don’t know yet). We know already that SUSY does not predict a Higgs below 150 GeV.

  17. Georges says:

    Supersymmetry is a fact of nature. At lest according to Warren Siegel, who writes since many years: “Thus, particle theory predicts supersymmetry.” (See his page http://insti.physics.sunysb.edu/~siegel/vs.html )

    Siegel obviously has a special view of nature, one that many others do not share. But if you want to make a career in particle physics, you better follow Siegel and Motl instead of those many others who prefer fact to fiction.

  18. Holycow says:

    Time will tell what’s fiction and what’s fact. And the future will be of the daring. Zwicky’s name will be remembered and those who opposed his ideas are already forgotten.

  19. joke says:

    Ha ha,

    is Siegel’ s whole homepage not just a joke-page?
    He does not mean any stuff he writes there serious or does he?!

    The joke-papers on it are really funny and give one a good laugh 🙂

  20. edg says:

    Maybe the dark halo is very different to the standard one.
    See http://arxiv.org/abs/1103.6091: a WIMP with mass in the TeV range and a rotating dark disk could be a viable solution for DAMA and the recoils measured by the other experiments.

  21. Geometrick says:

    Supersymmetry is not a fact until we discover those predicted particles. That is the objective truth.

  22. M. Wang says:

    Holycow,

    It is difficult to have a logical discussion with you because you consistently employ counterproductive debate tactics, but I will give it one last attempt.

    Claiming the others are trying to stop research into SUSY is a plain straw man attack, because I have not seen anyone here making that argument. What everyone here is saying is, instead, that previous SUSY predictions have been largely ruled out, and therefore Bayesian logic dictates that SUSY should be treated as a far-out idea unlikely to have relevance to this universe. Research into such ideas is still part of science, but they should certainly not considered mainstream.

    “You have to read more.””Your take on this is really a disgrace.””So, even Peter should be able to understand this allegory” These are all ad hominem attacks that serve only to degenerate the discussion into name calling.

    And finally, when you are not using these attack tactics, I find your logic impossible to discern. For example, “‘It would be equally misleading as e.g. saying that SUSY is a fact of nature.’ Not really. This might be true (we don’t know yet).” How does “might-be-true” leads to “not really” on a statement like “misleading…saying that SUSY is a fact of nature”, regardless of its true merits? If it is not misleading saying that SUSY is a fact of nature, then there is no might, could, would or any uncertainty.

  23. Eric says:

    M. Wang,

    The statement that SUSY has been mostly ruled out (even in the Bayesian sense) is completely false. I believe that what irritates Holy Cow is that yours and Peter’s statements are highly misleading in this regards. Obviously, this is related to your own biases and opinions, but I’m sure also it is related to fundamental ignorance about how science works.

  24. Peter Orland says:

    “Obviously, this is related to your own biases and opinions, but I’m sure also it is related to fundamental ignorance about how science works”.

    No, such statements are what betray fundamental ignorance. Remarks like this remind of what is said of professional tennis players. They have to be smart enough to play tennis, but just dumb enough to think it really matters.

  25. Shantanu says:

    Peter, If you have a multi-purpose experiment with different physics goals (such a Super-K), then sure if you have some people working on proton decay
    it is fine. But beyond a point, I am not sure its worth investing in building dedicated proton decay experiments, esp. if most well motivated theories continue to be ruled out
    in the 80’s building a dedicated magnetic monopole search experiment would make sense, but not now.

  26. KD says:

    Just to state the obvious. SUSY is a general idea with many specific incarnations. Those specific incarnations (and those only) can be falsified experimentally.

    Once a stage is reached where most popular incarnations are falsified one may start to doubt the general idea.

    KD

  27. felix says:

    Among all the envisioned possibilities at LHC, SUSY and large extra dimensions are the few outcomes that will bring a paradigm shift to physics. Most other speculations are merely mundane QFT theories built upon the old paradigm of gauge theory and spontaneous symmetry breaking. They are nothing but simple generalizations within the good old SM framework. I dare say that if the new physics that’s discovered is among this boring category, then the theorists behind it wouldn’t even get a Nobel prize.

  28. Bobito says:

    Too many take too seriously the idea that what is science is what can be experimentally falsified.

    What is science is what can be justified by experiments. This involves falsification, but there is more to it.

    The ether was a good idea that did not correpsond to reality.

    Right now there is not much (if any) experimental evidence that suggests that SUSY, in any form, is true (in the platonic sense). It’s simply a bad scientific attitude to say that what has not been ruled out is still credible. What confirmed general relativity in the minds of professionals wasn’t that it couldn’t be falsified (that’s not even clear yet). Rather it was that the predictions it made related to Mercury’s orbit coincided with observation (not even yet experiment – that came later). The acceptance of the theory was based on positive confirmation – and it didn’t come after years of null results.

    The success of such mathematical theories as general relativity or the standard model has ruined a lot of physicists educated in recent decades. Those working in the 50’s and 60’s mostly had some direct experience in engineering type activities in a war, and were able to distinguish between theory for its own sake and theory that grapples with real physical questions. That’s been lost to some extent. The success in mathematics of some theorists, e.g. Witten, has further confused the scene. However, as much as the geometrical-topological theory of higher dimensional manifolds is beautiful and deep, it has yet to find any (!) really deep application in genuine physics. Better to levitate a frog.

  29. Mitchell Porter says:

    felix says: “a paradigm shift to physics”

    You can see a paradigm shift in theory happening at the KITP program discussed in a previous post:

    http://www.math.columbia.edu/~woit/wordpress/?p=3611

    There is an extraordinary convergence among gauge theory, string theory, and twistor theory taking place. It’s as if they are all different ways of expressing the same thing. It’s being understood first for highly supersymmetric field theories, but there’s every reason to think that these new perspectives will extend all the way to the standard model, which is after all a gauge theory.

    Even without the LHC, then, big things would be happening, but all this is happening at the same time that we’re going to get the facts on electroweak symmetry breaking. But the point I would emphasize is that, even if neither Higgs nor supersymmetry is revealed at the LHC, even if every single beyond-standard-model phenomenological theory ever proposed is wrong, all the years of theory since mid-1970s have not been wasted, because they were indispensible in bringing us to this new convergence of mathematical perspectives, in which theories known for decades are proving to contain all these hidden properties.

    AdS/CFT and the twistor string were the breakthrough ideas, and as Arkani-Hamed mentions in his talk, now connections are being made to a great body of mathematics which had not previously played a part in physics, such as the theory of motives. With respect to string theory, what may be happening is that strings and branes are showing up as universal structures in quantum field theory, with compact extra dimensions corresponding to the moduli space of degenerate ground states. (That’s how it works in AdS/CFT.) It may turn out, not that string theory picks out a unique field theory as the theory of everything, nor that string theory has nothing to do with reality, but that string theory is one of several equivalent pictures available for a very large class of field theories, one of which describes our world.

  30. Peter Woit says:

    KD,

    The problem I’m trying to point out is that what’s a “popular incarnation” of SUSY keeps changing. For instance, it used to be that for a choice of SUSY parameters to be popular, it had to have a viable WIMP candidate to explain dark matter. Since a couple days ago, that may no longer be true. I’m sure that SUSY phenomenologists are hard at work on new plots of “favored” regions of parameter space, different than the old ones, since the old ones have been at least partly ruled out by XENON100.

  31. Peter Woit says:

    Mitchell Porter,

    That’s just nearly pure unadulterated hype. String theory has a long history of taking a very complex theoretical situation and claiming much more for it than there’s any evidence for. It seems that nothing has been learned from the results of that.

  32. Benito Callas says:

    SUSY and large extra dimensions are the few outcomes that will bring a paradigm shift to physics.

    Well, no. There could be experimental results that do not fit into any known theoretical framework that force a paradigm shift. In that case the Nobel you mention would go not to theorists but to experimentalists.

    On the other hand, I don’t see how SUSY could possibly be considered a paradigm shift, since it has been the de-facto paradigm for the last three decades.

  33. Holycow says:

    M. Wang,

    I don’t even know what “counterproductive debate tactics” means. But I sure agree with you that it is very difficult to have a logical discussion with some of the people here.

    I don’t think I claimed there are people trying to stop research on SUSY. I’m not paranoid. I’m just sick of bloggers saying SUSY is dead, or nearly so, when they should know better, especially thinking of what journalist can make of it. Why I feel strongly about this?: first because I happen to think SUSY is the best BSM idea in the market. Second, because I hate inconsistent crappy logic. I said it before and I’ll repeat it: experimental searches are bloody difficult, even when you know that the particle should be there. Remember the top. When the lower limit on its mass kept increasing and increasing who thought the top was a far out idea? There was a range for it to be found, we knew it should be below 200 GeV, and till the limit reached that point the idea was pretty much alive. So, Bayesian logic, my ass.

    The same holds for the statuts of SUSY searches (only much more difficult this time). Till the limits reach into the few TeV masses the search is on, the idea is alive and it’s in fact the most relevant goal for LHC besides the Higgs. If you don’t like it, too bad, but don’t discharge your frustration on the logic of scientific research.

    “These are all ad hominem attacks that serve only to degenerate the discussion into name calling.” Agreed.

    ““‘It would be equally misleading as e.g. saying that SUSY is a fact of nature.’ Not really. This might be true (we don’t know yet).” How does “might-be-true” leads to “not really” on a statement like “misleading…saying that SUSY is a fact of nature”, regardless of its true merits? If it is not misleading saying that SUSY is a fact of nature, then there is no might, could, would or any uncertainty.”

    OK. I didn’t say I support the claim that SUSY is a fact of nature. What I wanted to say is that “SUSY predicts a Higgs below 150 GeV” is a false statement, while we don’t know yet if “SUSY is a fact of nature” is true or false. Is that clear enough?

  34. Holycow says:

    Peter, you spend a lot of time fighting “hype” but then you fall into the hype-logic yourself. If some people wanted to promote their SUSY models or preferred regions of parameter space this shouldn’t fool you into thinking they are right. You do well in fighting such hype, but fight the hyppers, not the theory.

    I don’t care what the “popular incarnation” of SUSY is.
    Do you think somebody really thinks the CMSSM is the true BSM theory? It just serves a useful purpose to tune the experimental searches and the needed triggers, but SUSY is not over if some particular incarnations of it are ruled out. They have to be ruled out before we get to the real model.

    But in your mind, SUSY doesn’t exist, and I have the feeling that no amount of arguing will ever convince you that the discovery of SUSY is a logical possibility not ruled out at all.

  35. Peter Woit says:

    Holycow,

    To make clear what I think (and continually specifying that here SUSY=any of the known SUSY extensions of the SM, not something more general).

    1. The discovery of SUSY is a logical possibility not ruled out at all. But the world is full of implausible ideas that are logical possibilities, not ruled out.

    2. From the beginning SUSY was not a very compelling idea, since it doesn’t really explain anything about the SM.

    3. The continuing lack of any evidence for SUSY at LEP, in precision electroweak results, proton decay searches, dark matter searches makes the idea quite implausible.

    4. The last hope for SUSY is the LHC, which has already ruled out a lot of possible parameter space. There was some hope that dark matter searches would find a SUSY WIMP, but that had started to become unlikely, became even less so last week.

    5. Over the next few years better dark matter experiments will put even tighter constraints on SUSY WIMPS, and the LHC will rule out more parameter space. Each time these new results come out, SUSY advocates will produce new plots showing that it’s likely to be just around the corner, just a bit past the latest limits. I and other bloggers will accurately describe the situation as more and more nails firmly closing the coffin on SUSY. One notable exception to this will be Lubos.

    6. Anonymous commenters here will attribute skepticism about SUSY to ignorance. A large part of the particle theory establishment will go to its grave still convinced that SUSY is a wonderful, beautiful idea, with experimental confirmation just around the corner, and will promote this idea to anyone who will listen. As years go by, fewer and fewer will listen.

  36. Holycow says:

    Good enough. I’ll keep a copy of this for future reference. 🙂

    One simple reply, as I’m tired:

    #1 For you, everything is equally likely? Cultivate your taste.

    # 2. The existence of a third generation doesn’t solve any problem. Or does it? SUSY has the potential of solving several problems and explaining puzzles of nature. Go read some textbook on the subject.

    Do you know of any other BSM scenario at the TeV scale for which the lack of experimental evidence is less strong than for SUSY?
    #3. down

    #4. SUSY WIMPs are still a healthy possibility. Just in case, study gravitinos as DM candidates, if you wantyour claims to be as strong as you say. And, sorry, experiments exclude things before discovery. It would be nice if you just turned the experiment up and lots of new exciting stuff would pop up. Maybe in a different universe. If you don’t like this one, go somewhere else!

    Do you have a sorcerer’s ball? #5 irrelevant.

    #6 what’s the point?

  37. Peter Woit says:

    Holycow,

    Where did I say all things are equally likely? I definitely have my tastes, although you don’t like them. SUSY is more likely than some, less likely than others. On an absolute scale, I happen to think it’s pretty unlikely. Maybe more likely than black hole production at the LHC…

    I’m very well aware what the arguments are for SUSY, about which problems and puzzles of nature it is supposed to solve. I just happen to think those arguments are weak. If you can’t find those arguments here, a large part of a chapter of the book I wrote deals with the issue. The “you should read a basic textbook on the subject” argument is just juvenile, I’ve noticed it’s a favorite of those who don’t have a real scientific argument of their own.

    Sure, the best argument for SUSY is the lack of other good ideas. Doesn’t mean it’s a good one though.

    #6 The point is that I’m showing off my predictive powers, successfully it seems…

  38. Georges says:

    Peter, here your efforts (“there is no susy!”) are compared to those of El Baradei (“there are no weapons of mass destruction!”) : http://physicswithoutideology.blogspot.com/2011/04/woit-and-elbaradei-weapons-and-standard.html

    All the best to you!

  39. Holycow says:

    Peter,

    So, what do you think LHC will find besides the Higgs?

    “If you can’t find those arguments here, a large part of a chapter of the book I wrote deals with the issue.”
    Thanks, maybe I can find your book in some library. I’m not buying it 🙂

    “The “you should read a basic textbook on the subject” argument is just juvenile, I’ve noticed it’s a favorite of those who don’t have a real scientific argument of their own.” It’s rather being tired of repeating the same well known arguments.

    “Sure, the best argument for SUSY is the lack of other good ideas. Doesn’t mean it’s a good one though.”

    That’s a matter of taste and in the end nature will tell. Coming back to Georgi’s boutade (“Why I would be sad if a Higgs boson is found”), I’ll be happy with whatever LHC brings up. I’m more interested in finding out how nature works than proving my option is realized in nature. Can you say the same? Would you be happy if SUSY turns out to be the way nature is?

  40. Yatima says:

    “So, what do you think LHC will find besides the Higgs?”

    How about

    “So, what do you think LHC will not find besides not the Higgs?”

    Seriously, this is getting tiresome. I though popularity contests where for Italian Saturday Night TV.

  41. Peter Woit says:

    Holycow,

    My general point of view is that the SM is a fantastically beautiful and compelling structure, with the most problematic part of it the electroweak symmetry breaking mechanism. So, if I get to choose, I’d like the LHC to find not a scalar Higgs with the expected properties, but some unexpected evidence that leads to finding a better electroweak symmetry breaking mechanism. Of course I don’t get to choose, and will be very interested in whatever the LHC does find, even if it is SUSY. Actually I suppose I’d rather have some form of SUSY than the all too possible result that may come out of the LHC, a Higgs exactly as predicted and nothing else. Now, that’s going to be depressing…

  42. Holycow says:

    Cheer up! It’s gonna be SUSY all over the place! 🙂

  43. Georges says:

    Susy all over the place?

    – Monopoles?
    – Proton decay?
    – Large electric dipole moments?
    – Sparticles?
    – Many Higgses?

    In fact, even the wikipedia entry on supersymmetry does not list any experimental prediction. One gets the impression that the supersymmetry crowd is going the way of the string crowd, with the statement:

    “We do not make predictions, but we know that we are right.”

  44. Holycow says:

    Well, if the wikipedia doesn’t list any prediction I should consider seriously giving up on SUSY. 🙂

  45. Younghun Park says:

    The gravitational wave is not found, but, no one gives up the general relativity. When will it be found? We don’t know.
    The gerneral relativity is perfect? No!

    We can’t give up SUSY and String theory even if that is not found in experiment. Some concepts in SUSY and String theory are useful, very useful to make the better physics.

    We must not give up the all of SUSY and string theory.
    We must use the some usefulness in SUSY and string theory
    for the next advanced physics.

    What is useful in SUSY and String theroy?
    It’ up to you!

  46. Peter Woit says:

    Yonghun Park,

    One difference is that there actually is quite a lot of evidence for GR, while there is zero evidence for SUSY/string theory. Even on gravitational waves, the GR predictions have been indirectly tested (pulsars).

    Theories that never pass experimental tests or predict nothing should be abandoned, ones that pass experimental tests are the ones you know are worth trying to build upon.

  47. Bernhard says:

    Peter,

    I think one should not give the impression SUSY and Strings are the same thing. Of course you know that, but when you say “zero evidence for SUSY/string”, someone could get the wrong idea.

    Now I think the worst thing about SUSY is something I already discussed in this blog is that since LEP and with the LHC going to new parameters space, one of the most advertised things about SUSY, the “solution” to the hierarchy problem is looking less and less a “solution”. But of course there is still some room for it. So I agree with those who say we should wait.

    After 2012, as far as I know the situation should change. I am involved in an LHC experiment searching for SUSY or not SUSY. If SUSY is not there I want to be one of the people to rule it out.

    In any case the absence of a WIMP is bad, but for people working with R-parity breaking SUSY perhaps not a big surprise.

    In any case, SUSY is not dead at all, just looking less likely. The difference between the top quark history is that the heavier the sparticles the worse is the solution to the main motivation for SUSY exiting in the first place. The top quark could not have been too heavy but being light or heavy did not affect the motivation for its existence.

  48. on the way out says:

    SUSY will be abandoned only when something else comes along that does a better job of explaining things (and making successful falsifiable predictions). Just as the ether was abandoned only when relativity came along and did a better job of explaining things and making successful testable predictions. But for SUSY to be abandoned, the accelerators must find *something* BSM (suspicious bump? it will need more than one bump), and (i) SUSY must fail to explain it satisfactorily, and (ii) a “new theory” must do a better job of explaining things, and (iii) don’t forget the testable falsifiable predictions, the new theory will win only when it passes this step. But SUSY per se will never be abandoned, it will get displaced. So it was with the ether.

    Consider also the J/psi and other peaks (psi’). The quark model could explain all the peaks in a natural way (and predict the chi states and D mesons their properties ~ decays, selection rules, etc). Other models (S-matrix) could not do such a good job. One needs new bumps.

  49. Bobito says:

    Mitchell Porter:

    It’s very difficult to take seriously as physics any discussion that involves motives. This is taking something from the deepest reaches of number theory and algebraic geometry and imposing it on the physical world. It’s the same error that macroeconomists made when they took dynamical models from physics and tried to use them to interpret economic markets.

    Knowing too much can be a terrible impediment to understanding.

  50. Peter Woit says:

    Bobito and Mitchell Porter,

    When Arkani-Hamed spoke at Columbia, he mentioned the connection to motives, referring to discussions with Goncharov. He also stated quite clearly that he had no idea what a motive is.

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