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    SUSY: A Matter Of Prior Beliefs
    By Tommaso Dorigo | May 14th 2012 04:44 AM | 50 comments | Print | E-mail | Track Comments
    About Tommaso

    I am an experimental particle physicist working with the CMS experiment at CERN. In my spare time I play chess, abuse the piano, and aim my dobson...

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    In this sorry age for Supersymmetry (SUSY) phenomenologists, it is quite easy to step on an aching toe while discussing the results of the Large Hadron Collider experiments, whose results have let these physicists down by excluding the presence of SUSY where most of them used to put their moneys until yesterday.

    The knee-jerk reaction I frequently observe (e.g. see the thread of my recent post on the cMSSM) in the most stubborn SUSY enthusiasts is to seek refuge in a concept which could be summarized as follows: "There is only one true realization of SUSY in Nature, and one point of the parameter space which corresponds to it; the fact that the LHC has kept excluding parameter space points that do not correspond to the true realization of SUSY says nothing on the correctness of SUSY anyway".

    Now, let us step back for a second and make a few simple-minded examples of the implications of this kind of reasoning, to put it in the correct context.

    1) In some cultures a popular game played in special events is to hide a small coin or jewel in a big cake; everybody then gets a slice, and the person who finds the precious treasure can keep it. Now imagine you play such a game, and you start eating your slice bit by bit, to be sure you are not gulping down the treat with the cake. You keep finding nothing, and your dish is soon close to empty; only the tip of your slice remains to be checked. You therefore now grow extremely excited: surely you're going to find it in the next bit !

    2) You arrive at a deserted train station in the evening. You know that there's one train exactly every hour to your destination; however, you do not know the minutes at which trains pass. You also seem to remember that at some time late in the evening trains stop circulating. You sit and wait, and after 58 minutes have passed your train has not come yet. You then rise from the bench and pick up your suitcase, certain that the train is about to arrive.

    3) In a science-fiction story (I believe it is Ray Bradbury's "The Martian Chronicles", but I could be mistaken) a man decides to seek the help of a private detective. The detective explains that his client can be confident the case will be solved: he failed to solve the previous 150 ones, so it's extremely improbable that he'll fail on this one, too.

    In the three above examples, there is an obvious flaw in the reasoning of the protagonist: a wrong a priori assumption. The failure to account for the unknown probability that reality is according to one's wish is a childish mistake that we sometimes fall in even as adults.

    What SUSY enthusiasts in fact do when they resort to the "Nature chose elsewhere to hide" argument is to manifest that their prior belief in SUSY being the correct theory of nature is 100%. This, in a Bayesian formalism, can be mathematically described as a "point mass" prior probability density function (PDF): a Dirac delta function, containing all the probability at one value (whatever value we choose to describe "SUSY is true" on a real axis). Now, the problem with a point mass prior PDF is that no experimental observation -none at all- inserted in the Bayesian equation can produce a posterior which is different from the prior: a granitic belief cannot be shaken, regardless of the evidence against it !

    I believe Science progresses more rapidly if scientists keep their minds open to the widest range of possibilities. Well, let me restate that: I believe Science does not progress at all if scientists fail to do so ! I am therefore inclined to believe that choosing a point mass PDF for one's beliefs on the correctness of a unconfirmed theory is a wrong, anti-scientific attitude. I certainly acknowledge that SUSY is a beautiful idea, and I indeed would be happy if it were found some day (even better, if I myself found it ! I am indeed searching for SUSY particles in my research time with the CMS experiment!); yet the failure to observe SUSY as we raise the energy of proton-proton collisions and the accumulated size of our datasets in ATLAS and CMS cannot be dismissed as "no information". It is important information !

    Keeping oneselves anchored to a point-mass PDF that "SUSY is correct" equates to dismissing as garbage all the negative results of the LHC searches. I will say more: it equates to saying that it is useless to do experimental research, because SUSY might be hiding where we have no access with particle collisions or other experiments. Given that, and given that we must already be sure that SUSY is correct, why searching for it ?

    I am confident, though, that the attitude of those SUSY enthusiasts who choose the point-mass PDF is going to change if we continue excluding parameter space points at the LHC. Phenomenologists are pragmatic and smart people (someone funnily used the word "street-smart" in connection to one of them in the comments thread I mentioned above), so even the stubborn among them will soon choose some other point mass to anchor themselves and their careers to.

    Comments

    lumidek
    This is just vague, non-quantitative babbling meant to justify your pre-decided dogmas. The fact is that the elimination of 2/3 of a parameter space – and this is arguably a huge overestimate – would still be an extremely weak piece of evidence for the invalidity of SUSY. This boils down to this calculation:
    http://blog.vixra.org/2012/05/10/bayes-and-susy/ 

    A more general calculation of the same thing is here:

    http://motls.blogspot.com/2012/05/thomas-bayes-and-supersymmetry.html 

    As someone stated at a different place, the conclusion of the calculation above is that the absence of evidence isn't the evidence of absence. Of course, in all these debates, the discussion is about the precise numbers but the precise numbers are such that the exclusions accumulated by the LHC so far are equivalent to less-than-one-sigma evidence against the SUSY. In any other context, the existence of less-than-one-sigma bumps sold as an argument for or against something would be ridiculed. But when it comes to some key dogmas underlying your unscientific opinions about particle physics – such as the dogma that SUSY can't be right – you're ready to sell less-than-one-sigma bumps as proofs.

    If you think anything else, you are making a brutal mistake in the way you try to use your brain if you have any.
    If one's prior probability of SUSY is very low to start with, the elimination of 2/3 of a parameter space reduces the subjective probability to 1/3 of its prior value. But this approximation becomes very invalid once the prior probabilities are close to 50 percent or higher. And they should be because if someone thinks that a non-falsified prior probability is much smaller than 50 percent to start with, he suffers from dogmas – by definition. For 50 percent or so – one is neutral about SUSY Yes/No to start with – the decrease of the probability by the 2/3 exclusion is very weak.

    At any rate, you're rather likely to be proved wrong by the LHC in a foreseeable future. You will say that it's a shocking surprise but it won't be a surprise. The absence of a signal in the first 5/fb of the data at 7 TeV doesn't imply the absence of a signal in the first 15/fb data at 8 TeV, assuming any reasonably scientific standard for an "implication".


    You may try to populistically scream that if 6,000 physicists work for a year and write dozens of exclusion papers, they must have an impact. Well, they have an impact on the detailed models and regions of the parameter space that are being investigated by the phenomenologists and model builders. But their impact on the question SUSY Yes/No may be quantified and it is equivalent to a less-than-one-sigma bump in a graph. This result of the collective ATLAS and CMS efforts is easily beaten e.g. by a single paper by Christoph Weniger who finds traces of a 130 GeV dark matter particle in the Fermi gamma-ray data. It's easy to calculate that there's almost no evidence for or against the big SUSY question coming from the LHC papers so far whether or not someone finds this fact inconvenient.
    "absence of evidence isn't the evidence of absence"
    Surely that depends on how hard you're looking! Right now I have no evidence that I'm wearing a hat. If this lack of evidence persists even as I get up from my desk and go look in the mirror (or, for that matter, simply touch my hand to the top of my head), then the absence of evidence for a hat has become pretty strong evidence for the absence of a hat.

    lumidek
    "Surely that depends on how hard you're looking!"
    Not exactly. You may be looking very hard and spend your life's energy or thousands of years by searching for something and you don't find it. But it still doesn't mean you've proved that it doesn't exist. Whether the evidence for absence may be extracted from the absence of evidence depends on the objective numbers what the probability that the thing could be hiding would be if a different explanation were right. If the probability in the alternative explanations doesn't drop 1,000,000 times, then you have no 5-sigma-equivalent evidence of absence, regardless of the amount of effort you have dedicated to the problem. Results are not the same thing as efforts and it's the results and not efforts that matter here.


    In this particular case, one could argue - at the sociological level - that the 6,000 people in ATLAS and CMS have worked really hard to find SUSY and they haven't found it for more than a year, ignoring some secret work in progress that may be developing a different conclusion. But this hard work doesn't mean that they proved or almost proved its absence – in the general sense – that they have proved that it won't be discovered in the next year. They haven't proved anything of the sort as a simple calculation shows. A discovery would make a big "discontinuous" change, a non-discovery makes a hugely smaller, incremental impact on the probabilities of things.

    A calculation shows that those 50 or how many SUSY exclusion papers from CERN are not at all equivalent to seeing that there's no hat in the mirror, despite some demagogic comparisons of these two situations that are not similar at all.
    As Clara argues, every child knows that not finding Santa Claus doesn't mean that he does not exist http://physicswithoutideology.blogspot.de/2012/05/why-supes.html

    Maybe we are too harsh an Lubos; let him believe in Santa Claus!

    Thor Russell
    Come on, this article seems purely intended to start a flame war, especially as at one stage it looked as if the Higgs was running out of places to hide, yet your belief never faltered. (not that I am criticizing that) Why not just name Luboš in the title of the article as it seems to be written for him.
    Thor Russell
    lumidek
    I also had a feeling that Tommaso addressed it to me but wasn't courageous enough to write my name down....

    Your analogy with the Higgs allowed intervals is very appropriate. When we're approaching a discovery, we're inevitably able to eliminate increasingly large portions of the regions that were possibilities just a year ago. This just means we're learning something about the details of the model. For Higgs, the discovery could actually take place well before the exclusions of the most of the parameter space because its signals are sharp as a function of the Higgs mass. But this didn't occur. For SUSY, the signals are much more widespread as functions of the superpartner masses so we must clearly expect to exclude an even higher fraction of the parameter space before the discovery - at least one able to find out the masses of the new particles – can actually be made.

    To have the equivalent of a 3-sigma evidence against a theory with a parameter space (against all of its points), one must obviously eliminate at least 99.7% of the parameter space and the required percentage becomes even higher if the prior probability for the theory was above 50 percent or even higher. So if someone neglects signals that are smaller than 3 sigma, he should also consistently ignore the exclusion of a percentage of a parameter space - when it comes to the question whether any point of the parameter space is right – is the excluded percentage is smaller than 99.7 percent. 

    Paying attention to a less clear exclusion is equivalent to paying attention to smaller bumps than 3 sigma and in combination with the desire to ignore such small bumps, it proves that the given person is inconsistent and uses double standards according to his dogmas.

    I am just reading a paper on focus point in MSSM

    http://arxiv.org/pdf/1205.2372v1.pdf 


    with large A-terms, something that eliminates at least one complaint by Nima. Of course that as long as they can find regions for which the fine-tuning is as small as 1-part-in-100, it's as valid phenomenology as a year ago and the impact of the LHC exclusion papers on the legitimacy of this research so far is pretty much zero.
    dorigo
    Hello Thor,

    no start of anything. In fact, after the person you mentioned crossed the line here,  by posting something in a previous thread which could cause him to be brought to court for libel by a third person (who incidentally had nothing to do at all with that ongoing discussion) and then calling me names and going postal one too many times, I am altogether ignoring him. I know he can get back to normal if he does not skip his medications, so he still has a chance to be welcome here again; but for the time being he is in purgatory as far as I'm concerned.

    Rather than a start, this is my reply to the generic argument discussed in the post. Re-read it with a unbiased eye and you will realize there is nothing inflamatory; just a bit of irony, if you want.

    Cheers,
    T.
    lumidek
    dr tmms hv lrd tld y bt lt m mphsz nc gn tht wht pstd ws tr m rd t rpt t n n crt r n mmrl jrk f dfnd th prsn cnnctd wth th crms gnst hmnt nd bcs r lctd n sm whch hs lws gnst r bhvr my s f cntn t sggst dspt ll th fcts tht hv wrttn nthng tht ws nccrt mrvr r  lr f sggst tht r gnrng m s thr hs fgrd t nd b sr h wnt b th nl n ths txt ws wrttn prmrly bcs f m nd my nd phls dscssn f th mpct f th xclsns

    Update: which asshole has destroyed my comment, apparently by erasing all the vowels? Could you, Hank, please kill the criminal?
    blue-green
    Are you still here Luboš… Tomm? Perhaps this is akin to the missing 23rd letter in the Hebrew Alphabet, missing vowels and worse, the dearth of VERBS in physics and mathematics. “In the beginning was the verb”.

    My man-in-the-woods view of SUSY is that her math and search make my brain HURT, so I don't want her to be true.

    Toss me a verb or I'm with jonathan (below). Einstein's Riemannian Geometry is true enough that I made the effort to learn it. With SUSY, I'm hesitant. She's high maintenance. Besides, with all of the DUALITIES iso-morphing one corner of mathematical-physics onto another, why be CHOOSY?
    lumidek
    Dear blue-green,
    a good cat. Maybe if you dedicated more time to SUSY learning, you would start to appreciate the inner beauty of SUSY. But even if you wouldn't, it's completely irrelevant for the validity of SUSY which doesn't depend on human or kitten's emotions.

    Dualities in string theory and field theory show that many descriptions are equivalent - they're just good starting points to address a "moduli space" of theories from a corner - but SUSY is exactly one of the aspects of the dual descriptions that isn't changed. If one description has a certain degree of SUSY, the dual descriptions have the same degree of SUSY. SUSY is invariant of the duality maps and is actually the main mathematical tool that allows us to find the dualities, test them, and that allowed Nature and mathematics to make this dualities possible in the first place. 

    So one may talk about being choosy when it comes to one of the dual, equivalent descriptions. But by making such a choice, he's not choosy at all when it comes to SUSY because the amount of SUSY is exactly the same in all the descriptions. The generators of SUSY are the same. SUSY is a completely physical symmetry so it doesn't depend on the description, unlike some redundant degrees of freedom. (Well, SUSY is also a gauge symmetry, in SUGRA and its completions, including all of string theory, but in asymptotically flat or well controlled superselection sectors, a part of the gauge symmetry - local SUSY - becomes global and doesn't have to annihilate physical states. It's surely useful to organize excitations etc.)

    Best wishes
    Lubos
    vongehr
    Yes, somebody's quality is going down along with the output of the LHC, so now chess problems and flame wars become articles instead of blogs. What really is funny is how with the FTL neutrinos, semi-religious priors were defended by the same bloggers who now rail against them.
    There we have Mr. Superluminal Jump again! Maybe you can write an article on how you recovered from your shattered "million times faster than light" beliefs? Might soon come in handy to SUSY believers.

    my god ! I thought you scientists were all sensible, well-balanced people ! I could've studied physics after all. Thanks for putting me straight ;) I learn so much from this blog, in so many ways. Also thanks for the interesting article.

    dorigo
    Hah Jonathan, that's a delusion. Scientists are just as dumb as the next guy for ordinary stuff - there's all kinds around.
    Cheers,
    T.
    Hi Tommaso,

    For science to be so successful, I always imagined that in order to really be open to critique, and evaluate competing opinions and theories, there must be something of a 'selection pressure' towards open and well-balanced minds. Are you saying that is not your experience ? I myself am 'from the arts',
    and it seems to me that there is a selection pressure towards the 'sociable but whacky' :)

    J

    dorigo
    Well Jonathan, I have a high esteem of most of my colleagues, and then there are the frownable upon. For some reason they like to populate this column, too. But they aren't a representative sample... My blog attracts funny people, it seems :)
    Cheers,
    T.
    Hello Jonathan,

    I am not in particle physics, my field is biophysics and biochemistry. Unfortunately, I would have to say that most present day scientists are conformists. To become part of the exclusive group, i.e. become an academic, you must play by the rules of those before you who hold the 'keys' to the future. This group consists mostly of established scientists who are tenured academics and sit in on most of the grant committees to decide who gets funding. I have heard of/seen many cases where a researcher is trying to pursue a novel approach or idea and it does not get funded. Hence, the researcher then attempts to tie his novel project to a 'hot' topic so that he will get funded. This works and happens often. This is just one type of example of the conformity of the field, there are many more.

    Just for disclosure, no I am not one of those who has 'made' it, I just want to teach college level courses. For another example of the closed mindedness of academics, pure teaching is looked down upon very highly by the majority of my peers. 'What!?! You don't want to be doing research at Harvard!?!"

    Also, when I use I the term academics I am talking about professors at research universities.

    C

    An interesting and relevant article: http://arxiv.org/abs/1205.1568

    Tommaso,

    What we can say is that the theoretical ideas that led to a preferred set of SUSY parameters have not worked out.

    On the other hand, do you think that perhaps a null result in supersymmetry will be both as upsetting and as revolutionary as Michelson-Morley's null result? Does any reader know what they said back then, did they say that if we don't find the ether wind, then physics is moribund?

    Best wishes,
    -Arun

    dorigo
    Hi Arun,

    to me already the idea of the breaking of mass symmetry (without which SUSY would not have flown in the first place) is a bit too much to buy for an admittedly otherwise beautiful concoction. Now you will admit that the fact that everybody kept swearing the SUSY particles would be found by the next accelerator - starting from the early nineties on - has made the situation a bit awkward. Yes, SUSY may be at higher masses and may have been hiding there all along, but with an open mind we must admit that the chances are shrinking.

    As for the other part of your comment, I do not believe that NOT finding SUSY would be revolutionary.

    Cheers,
    T.
    Hi Tommaso,

    If you don't mind idle speculation - one reason theorists like symmetries is that they are pretty. But another reason is that it makes calculations tractable. We are naturally biased towards ideas that are easier to work out the consequences of, and the cure for every problem in particle physics has been to try to introduce more symmetries. The ultimate in adding of symmetries is superstring theory. Since symmetries are often not apparent, they must be "broken", and breaking them introduces fresh problems, for which the answer is - still more symmetry.

    With no proton decay and the failure of the simpler GUTS models, maybe Nature fired the first warning shot across the bow of the ship of physics, that more symmetry is not the answer; and maybe no supersymmetry will be the second shot. Just like the ancients seeking more epicycles and the 19th century physicists seeking a mechanical model of the ether despite the paradoxical qualities it would have, maybe we are on the wrong track with more symmetries. Just as it would have seemed inconceivable to those previous folks that there would be some other way to proceed, so it seems with us now.

    Maybe. Or maybe supersymmetry is around the corner :)

    rholley
    Every time you bring up an article about SUSY, I can’t help thinking of this:
     
     

    Robert H. Olley / Quondam Physics Department / University of Reading / England
    dorigo
    Great piece Robert, enjoyed that a lot !
    Cheers,
    T.
    Supersymmetry was invented to get around the Coleman Mandula Theorem.
    Problem: there are no sparticles around. Solution: Low-energy susy is broken.

    But does broken susy also get around the Coleman Mandula Theorem? It seems not.
    So why do all these people believe in broken susy? Can somebody explain?

    lumidek
    Dear Frank, the Coleman-Mandula theorem strictly speaking constrains unbroken symmetries only. It says that certain symmetries - most symmetries - cannot exist. Only the spacetime (Poincare) symmetry and internal symmetries (generated by Lorentz scalars) may exist. SUSY is the only loophole allowed by a generalization of the Coleman-Mandula theorem....

    So if SUSY is broken, there is really no new unbroken symmetry there, so one doesn't have to get around the Coleman-Mandula theorem at all. Coleman-Mandula theorem says that "there can't be too many exotic unbroken symmetries" so if one has fewer symmetries, it becomes easier to be reconciled with the theorem, not harder!

    The nature of SUSY breaking is being misunderstood by the laymen, too. SUSY is broken spontaneously in the same sense as the electroweak symmetry (by the Higgs field); if we describe the SUSY breaking by 105 new parameters, it's just an effective description of the effects of the SUSY breaking mechanism - those parameters would be fully calculable if we knew the exact physics behind SUSY breaking (and they are semicalculable in many more detailed SUSY scenarios). In fact, in both cases, the symmetries are local, gauge symmetries in the real world (in the case of SUSY, it is local because the world contains gravity and SUSY turns it into supergravity) and gauge symmetries can't be broken at all. They're redundancies of the description.

    There are lots of things to be said here and lots of subtleties but broken SUSY surely doesn't contradict any no-go theorem, Coleman-Mandula or otherwise. It's straightforward to show that broken SUSY theories are totally consistent so there can't be any theorem that would ban them.

    Sensible people "believe" in broken SUSY because there exists a huge amount and many kinds of scientific, theoretical evidence (its role in string theory, the only consistent quantum theory of gravity; gauge coupling unification; dark matter particle candidate etc.) that it is realized in the Universe around us. We don't have any waterproof proofs that SUSY will be found but we surely have lots of evidence that SUSY should occupy a big part of phenomenologists' work.
    "I am confident, though, that the attitude of those SUSY enthusiasts who choose the point-mass PDF is going to change if we continue excluding parameter space points at the LHC."

    Well thats a funny thing to say Tommaso. I thought the whole point of your constructing this story was to argue exactly the opposite of what this sentence says!

    And I dont understand why you're talking about continuous variables and delta functions for a yes/no question. The prior probability for a yes/no question is an ordinary probability, not a density over anything. We can talk about density over parameter space, but I dont think Ive ever heard of a theorist who literally thought they knew the exact point of parameter space, making their prior probability distribution a delta function.

    Anyway Im among those who have high priors for SUSY for theoretical reasons, and of course I would like it if SUSY were discovered at the LHC, but it wont be a dramatic shift in my posterior probability. Naturalness is a very slippery business, of course, and I think its a bit risky to presume that the same definition of naturalness will be preserved from the more fundamental starting point.

    And there is clearly a very big point to learning about SUSY experimentally even if we have a near-100% prior probability that its realized in some form. Because the specific form of SUSY breaking will be extremely important, and in particular will be very interesting to compare to the ways of obtaining realistic models within string theory.

    dorigo
    Hi Clifff,
    about my sentence: all I am saying is that there is time to repent even for the most stubborn of SUSY enthusiasts.
    About your point that it is important to study where SUSY isn't even if we give for granted it is somewhere: of course this is a valid point. But it does not change my conclusions, I don't think.

    Best,
    T.
    The central issue is not so much what percentage of the parameter space is left, but what a SUSY theory that would leave no measureable impact on the excluded parameter space would look like and whether such a theory is really the kind of theory that the theoretical considerations that drove the proposal of SUSY theories in the first place still make any sense. If the entire data set in existence today had dropped in our lap without commentary all of the sudden today (which is sort of what happens each time a new theoretical physicists goes to graduate school, except that there is lots of commentary in that case), would anyone propose SUSY to address the unanswered questions we still have about particle physics today?

    Certainly, the original proponets of SUSY expected phenomenology to crop up at the TeV scale. It didn't. Whether those predicted phenomenological consquences were a central motive for SUSY is harder to say.

    Other non-LHC type evidence also needs to be brought to bear. One reason to introduce SUSY was to cancel out high energy divergencies in the calculations. Some of those divergences turn out not to be as great as one would naiively expect. Does that impact the motive for SUSY?

    Another huge motivation for SUSY is to provide a dark matter candidate in the form of the lightest supersymmetric particle. But, if observed dark matter whose content is not known but whose properties are increasingly constrained is a poor fit to a hypothetical LSP (since cold dark matter theories with 100 GeV+ dark matter particles increasingly don't seem to fit the data, which tend to favor lighter dark matter candidates), then the practical motivation to consider SUSY is greatly undermined.

    lumidek
    It is not true at all that SUSY has been excluded at the TeV scale. The LHC data totally allow the stop to be as low as 300 GeV, neutralinos to be below 200 GeV, gluino to be at 800 GeV or so, stau to be lighter as well, and so on.
    The amount of fine-tuning may be as tolerable as in 1 in 100 according to the present data, see e.g. the latest paper on focus point supersymmetry. Moreover, dark matter of the SUSY type may have been seen in the Fermi data, the 130 GeV line.

    Moreover, the calculation by Phil etc. takes all the "punishment for higher masses" into account. The prior probability distribution added whatever probabilities to various masses and it decreased with increasing masses, generally speaking. According to this distribution, the excluded region is almost certainly lower than 2/3 of the prior value which is equivalently to less-than-one-sigma evidence against SUSY as such, and I am talking about the very picture of SUSY that existed before the LHC - that means almost no evidence at all. 

    Nothing is undermined and SUSY may appear in every month of 2012 or 2014 just like it could appear in 2011. We don't know when but the odds per month aren't really going down as the energy and/or luminosity of the LHC is going up.
    Hi Tommaso,

    I'm a not a particle physicist, but I have a comment. First I understand that you particularly do not quite believe in SUSY, and your prior is significantly against it (which is perfectly fine). Also I think it is perfectly fine that some other people to be biased towards SUSY and their prior is different from yours (although their prior is still not a delta function in my opinion). So now what do we have as evidence(data)? Not much (for either of competing BSM theories). And indeed the evidence for SUSY is reduced ( by 25-75% depending on the exact priors and flavour of SUSY ) . That's bad, but it doesn't really change the game. Especially since we don't have a lot of competing theories with significantly increased evidence.

    So overall, I don't quite understand your attacks on SUSY.

    dorigo
    Hi SK,

    it is not an attack on SUSY, in any way. It is rather a criticism of some stubborness that I see around, in people who three or four years ago would claim we'd be seeing sparticle cascades the week after we turned the LHC on, and who now say their favoured models have yet to be touched by experimental test. Their being a moving target shows that we should not take their claims too seriously.

    Cheers,
    T.
    Ok. It make sense. But, still, I think that the excessive optimism of some people before the launch of LHC should not be the reason for excessive scepticism now :)

    Duh Luboš, 2/3 is an exceedingly ancient Egyptian superstition, and to hear you utter it is LOL. As for snobby priors, they are all second-rate in comparison with the One and Only True and Most Ancient One Theory, which is that all things are properly represented as divisions of One, so that the whole answer can only ever be one. Not only is this the only diplomatically correct theory, for reasons now acidly obvious, it is also the one and only theory with a reserved prior of one.

    But since it is a semantic theory, I'm afraid your empirical aspirations don't even make the scale. The only other point on this scale is reserved for mathematical errors. Ornery probabilities, mind you, are strictly restricted to plausabilities, with no bearing on actual truth.

    In my opinion the existence of supersymmetry is selfevident in the same way, like the existence of extradimensions. This concept has a good physical meaning in dense aether model (the supersymmetry of Russel's and Falaco solitons at the water surface, for example). In dense aether model every refracting phenomena or gravitational lens serve as a tangible evidence of extradimensions in the same way, like every force violating inverse square law in 3D space. The notorious example of supersymmetry are the photinos, i.e. the neutrinos, who play a role of superpartners of photons in dense aether model.

    The only problem is, the contemporary theorists cannot recognize the artefacts, predicted with not only foreign theories, but even with their own theories. For example the CMBR noise is tangible evidence of both extradimensions, both gravitons, both gravitational waves. But how to explain it to formally thinking theorists, who do adhere on local perturbative models and experimentalists, who are motivated in as prolonged research, as possible?

    It seems to me the article is saying, we haven't found anything that confirms the SUSY model predictions, maybe we should at least consider the idea that it is wrong and come up with an alternative. Sure you can make that "alternative" be SUSY is at a higher energy than we have looked at so far but that is always a way out forever. With that as excuse we can never deny the model and will always be able to save it. Is that really science anymore? The other alternative as that maybe we don't know what we are looking at and SUSY is hidden in our existing data. That is always a way out as well. How is that any better than string theory? We have no predictive test for SUSY if you use the last two ideas to keep it propped up. At some point SUSY need to be model with a difinitve test as to it validity, without that it is nothing but a neat piece of math.

    Shouldn't we consider the possibilty that SUSY is wrong or at the very least incomplete? After all we already know our two foundational models of the physical universe are wrong/incomplete since relativity and QM are incompatible as formulated. The evidence from the LHC and elsewhere is hinting that maybe we are missing something and that SUSY as model of reality is flawed.

    In dense aether model the observation of Higgs boson is dual to observation of CMBR density fluctuations at the cosmic scale. These density fluctuations follow the nested dodecahedral geometry of hypersphere packing, as described with root vectors of E8 Lie group. It vortices of dodecahedrons forms the "Penrose circles" on the sky and the do manifest with five characteristic maxims at the CMBR power. These density fluctuations are formed mostly with neutrinos and their dual version leads to the five Higgs bosons of supersymmetric model.

    The understanding, why the structure of space-time at the cosmological scale should mirror the structure of space-time at the quark scale is quite easy with water surface analogy of space-time in dense aether model. At the water surface the circular ripples scatter at the sufficient distance to individual solitons, which do interact mutually like the colliding particles and they undergo the hypersphere packing geometry of quantum wave packets (I can explain its principle in more details, if someone will be interested for it). In similar way the tiny ripples are scattered at small scales into longitudinal ripples of Brownian noise, the density fluctuations of whose do interact like tiny particles as well. In this way the water surface can serve as a simplified pocket version of observable Universe at much larger and smaller scales.

    Hfarmer
    You said it better than I could, which makes lots of sense considering our positions.  After all I am just a student.
    I made a innocent comment, that SUSY was in a sense "too big to fail".  Too much time, and too many resources have been staked on SUSY.  Then there are all the career's that have been spent on studying SUSY and almost nothing else.  All of that was and is riding on the results the LHC will produce. 

    All of us in academics know that financial consequences for such a failure are a real possibility.  Jobs would be lost, tenures denied, post docs not renewed and new particle physics projects may not go forward if SUSY is not found at the LHC.  I don't think it's likely that the international linear collider will be built only to find a whole lot of nothing. Congress will not give us the funding for that.  Such a result would damage the physics community here in Chicago.  

    So my feelings on this are like what Leon Lederman once said of the LHC.  "It's like watching your mother in law drive off a cliff in your new car."  

    I hope SUSY is found, but that does not make it real.

    Science advances as much by mistakes as by plans.
    Concerning dimensionalities, I think it fair to say that the Higgs(ish) signal has underperformed standard expectations. There is a confounding issue of some specific branches, but the global question of signal/ground discrimination remains, and it should be possible to quantify this by discriminant analysis. If detectors can be taken to respond in standard degrees of freedom, any additional df out there create space for the signal to vary undetectably, so hiding from us. But from what I understand its Kaluza-Klein-type theories that have the Higgs specifically varying in a fifth dimension. E.g. http://arxiv.org/abs/1204.0008; http://arxiv.org/abs/0901.0609. SUSY is not the only game veyond the SM.

    TD:
    On LM's general attitude (and despite grinding my teeth) I must applaud you for being far more tolerant than I could have ever been.

    dorigo
    Hi Paddy,

    deep down I know he can be a nice guy. It's just he can't help it sometimes. I joke that he is sometimes forgetting his medication, but there must be some truth in it -he at the very least is bipolar or something IMO. However I have had interesting discussions with him in the past, and he has even contributed usefully to these threads most of the times -if you can read between the offenses.

    Maybe I am tolerant. Or maybe I chuckle when people get angry at me and spill their venom, I keep my cool and that feels very, very good.

    Cheers,
    T.
    Hank
    I even had Lubos flip out on me one time.  It was a badge of honor.  I felt like I had 'arrived' in science media.
    Motl is well known arrogant psycho. With such comments you would be banned 4ever at the Motl's blog...

    http://backreaction.blogspot.com/2007/08/lubo-motl.html

    Till the confirmation of the Higgs Boson, the MSSM is not really the minimal SUSY, as you can just put each of W and Z in massive susy multiplets and then it amounts to three extra scalars, not the five of MSSM.

    The current debate in parameter-space is much like multidimensional scaling in statistics - when we need trans-dimensional scaling! That's roll-your-own territory.

    I think you are right, but since LHC does not see new things out there, its quite puzzling what the New Physics should be. Currently we know that SM works well up to sqrt(s)~ 8 TeV.

    Or, CMS/ATLAS might have data, that can give you a clue about the New Physics, but your signals are still within 2 sigma, and you don't know what's a rabbit and what's a ghost.

    p.s. As a theoretical physicist, I will wait until CMS/ATLAS give us hard data/evidence about the Higgs, and the Higgs mass. This will be the starting point for the new ideas, if SUSY still crashes.

    Best,

    Nick ;)

    The SF novel with the detective who failed 150 times is Mindswap by Robert Sheckley. Of course, there may be other books which use this joke, but Mindswap is the one I know.

    dorigo
    Thank you Adam! I think you are right...
    Best,
    T.
    "I believe Science progresses more rapidly if scientists keep their minds open to the widest range of possibilities. Well, let me restate that: I believe Science does not progress at all if scientists fail to do so !"

    The progress of science does not necessarily require that individual scientists change their minds, any more than evolution by natural selection requires that individual organisms change their DNA. It is possible that science progresses because of the death or retirement of scientists whose dearly held views do not conform to the latest evidence, and their replacement by newcomers who had the advantage of first encountering the new evidence with an open mind.

    dorigo
    What you write is correct, but it is not in contradiction with what you quoted. In the quote, "scientists" of course includes dying and raising ones, and the latter of course also need to keep their minds open to the widest range of possibilities.
    Cheers,
    T.