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    What You Think Of New Physics At The TeV Scale
    By Tommaso Dorigo | September 30th 2013 03:33 AM | 20 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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    A few days ago I posted the results of a poll ran on 50 or so participants to a workshop on the Higgs boson in Madrid. The poll consisted of six questions on the expectations one had on the possibility of new discoveries by present-day accelerators, as well as on the nature of the underlying theory of fundamental interactions, and on the nature of dark matter.

    The poll results were interesting to me since they showed how the general perceptions of HEP physicists has changed in the last five years, following the startup of the Large Hadron Collider and the observed absence of striking new physics signatures. I however reasoned that it would have been nice to see what was the perception among outsiders, too. People who read this blog make a good sample to run this kind of investigation, since you do understand -grosso modo- the issues and know the general status of particle physics and cosmology. Or maybe you are a biased sample, given that you read the blog of a die-hard sceptic. Who knows.

    Anyway, I invited readers of this blog to leave their own answers to the six questions in the comments thread. Actually I asked for answers to five of the six questions, since I found the sixth too technical and off-topic for a HEP audience and blog.

    I was pleased to see that the offer was taken by about three dozen readers, which are enough to extract some meaningful statistics from their answers. So let us see what you readers think of the issues raised by the poll.

    Your answers

    Question 1 was the one allowing for most possible answers: it asked "Concerning the hierarchy problem, which of these options is in your opinion closer to the truth?" and allowed for the six possibilities below:

    a) Low energy SUSY solves the hierarchy problem.

    b) There is no hierarchy problem, it is a misinterpretation of how field theory works.

    c) The hierarchy may be understood in the context of anthropic arguments, perhaps in connection with the existence of a landscape of string vacua.

    d) There is new physics above the TeV scale (e.g. compositeness, Randal-Sundrum, some technicolor version).

    e) There is a low scale string theory above a few TeV.

    f) Other

    Here the HEP audience of the Madrid conference had given a split verdict, about a quarter of them choosing each of the three first answers, and the remaining fourth opting for one of the last three. What you think is different: 50% believe that there is no hierarchy problem; 31% pick "other", and 10% pick low-energy SUSY and anthropics each.

    Question 2 was "Will the LHC and/or the ILC eventually detect non-standard properties of the Higgs boson ?". In Madrid 47% had said no. You are much more negative: 75% of you say no.

    Question 3 was "Will the LHC eventually find new physics other than the Higgs boson?". In Madrid 41% had answered no, but here we see 71% of naysayers.

    Question 4 was "Will dark matter (either WIMPS, axions, or other) be detected in the course of the next decade ?". In Madrid 75% said yes, here instead the optimists are only 39%.

    Question 5 was "Will we eventually measure non-Gaussianities or tensor modes or other cosmological new effects?". I had planned to skip this question, but you answered anyway. In Madrid the physicists had answered mostly no (54%), here we are surprisingly at 87% yes!

    Question 6, finally, was about string theory: "Do you think that String Theory will eventually be the ultimate unified theory?", and it allowed for a third answer beyond y/n: it could be said to be "a step in the right direction". 46% of the Madrid attendees had picked that third option, with the rest split between the two definite answers. Here we instead see an overwhelming majority of naysayers (83%), with the rest split between a yes and a "step in the right direction".

    What conclusions can we draw from your answers ? Well, first of all I will say that you are a dirty bunch of sceptics ! Jokes aside, you are much more pessimistic than insiders in judging our chances to make quick progress in the understanding of matter and the cosmos (if we exclude question 5, which I prefer to not consider). Second, it is interesting to note how string theory is not felt as promising among outsiders. But I should say that many of you who answered the poll are not properly outsiders: many are PhD students (25%), and a further 20% are insiders (theorists and phenomenologists).

    In retrospect, I think that indeed, there has to be some bias in the selection of readers of this blog (or at least, those who decide to contribute to the poll). String theory enthusiasts would probably be reading Lubos Motl instead, and since Lubos still entertains himself with defamation and personal attacks on me from time to time, they might just not want to mess with polls I run here...

    In all cases, I thank everybody who participated in this interesting experiment !




    Comments

    vongehr
    What conclusions can we draw from your answers ?
    That you should ignore them. Who but the ignorant can deny that ST is a step into the right direction with its providing of such clear examples of description duality as those between the string theories, that between gravity as curved space-time versus a mere force, even emergent, that between no surface or surface around a black hole?
    > Who but the ignorant can deny

    That high horse is getting a bit long in the tooth. Time for a trip behind the shed maybe.

    > such clear examples of description

    Huh. You seem to be talking about GR, if one squints a bit at the grammar.

    "This whitewashed presentation of history is how the elites want to spare themselves embarrassment but also, perhaps unconsciously, want to ensure conformity: Even while knowing that they do not have the truth, we are supposed to believe that only the officially labelled "experts" alone are clever enough to find out the improved truth and that if we instead look at anybody not being granted official expert status, we will only find silly stuff that is yet more wrong, much more wrong than the little tiny bit of detail that the experts may be still missing.

    We are to believe that the experts have the best approximation to the truth, which is the only truth we may hope to attain. In reality, the experts have first and foremost one thing: Attained a position of power where they may call themselves experts."

    http://www.science20.com/alpha_meme/should_we_trust_experts-80989

    It sounds like all your readers think the LHC particle physicists can just go home, since their work is apparently done. ;] I can't condone such defeatism! I don't know if my answers are still invited but here they are anyway.

    Question 1. A) Low-energy SUSY solves the hierarchy problem, although it may not be so "low" according to human standards. I very much agreed with the more split answer from the "other" category given by the Madrid attendee. If we roughly characterize the hierarchy problem according to the difference between the squared mass scales of the Planck minus the SUSY-breaking scale, as we should, then SUSY at the 10-100 TeV level still solves the vast majority of the problem. Its very likely that there is some anthropic bias at work, but I think the level of tuning in the completely non-SUSY Standard Model is just way too crazy for that to be the whole story. So some anthropic selection may tag-team with SUSY as the explanations for the naive fine-tuning.

    Im really at a loss how any serious physicists can simply denying the hierarchy problem exists. You could argue that naturalness is simply not a good principle in this situation, and the universe is in fact tuned with horrendously precise cancellations, but if you're going to say its a "misinterpretation of how field theory works" a lot of theorists will be extremely interested to learn what radically different formulation you are privy to, that is somehow completely at odds with the renormalization group and everything else we understand. Otherwise there is currently not much reason to think such a formulation exists.

    Question 2. Yes.

    Question 3. Yes, although my confidence is lower.

    Question 4. Yes.

    Question 5. No.

    Question 6. Yes. Very likely, yes. But the word "ultimate" is troublesome, and I wouldn't have included it. According to this formulation even some of the most enthusiastic string theorists might have to say "Its a step", even if its a very grand step. But I'm pretty sure, according to the intent of the phrasing, I would definitely answer "yes", even if it waits to be completed by other important insights – some knowable and some perhaps unknowable.

    Here again, to the naysayers, I'll be fantastically interested to see even the first seriously viable alternative. If you subscribe to the idea that string theory and related insights are all nonsense, like apparently most readers of this blog, then at some point there will have be some other framework with similar explanatory power. Im open to having my mind changed by new evidence, but right now that idea seems fantastically unlikely, in my humble opinion.

    Rick Ryals
    Cliff said:
    I'll be fantastically interested to see even the first seriously viable alternative.

    Something got missed way back when that will change QG so dramatically that you should not be surprised to find out that you have been chasing a unified field theory all along.  I know, we know better than that... based  on... flawed assumptions about incomplete theories...

    http://www.lns.cornell.edu/spr/2005-06/msg0069755.html
    http://www.lns.cornell.edu/spr/2006-02/msg0073320.html
    http://longbets.org/476/
    http://dorigo.wordpress.com/2007/10/18/

    hey, I had to take my shot, that'll teach you to ask for it... ;)
    John Duffield
    Cliff: I don't think the LHC particle physicists should go home. Instead I think they're struggling to find answers because they're asking the wrong questions, and they're forever looking "beyond the standard model" rather than "within the standard model". That's why I previously said I'd rather see a workshop entitled Why mₑ = 511keV? Yes, I was amongst those who said the hierarchy problem is a "misinterpretation of how field theory works", because as far as I can tell many theorists don't actually understand how the fields work. IMHO it's not an issue of some radically different formulation, it's an issue of having a concept of the reality that underlies existing formulation and phenomena. You don't need anything new for that, what you need is already out there in non-HEP physics like classical electromagnetism and relativity. For example, try writing a short paragraph explaining why the electron and positron attract one another. Then I'll do the same, and hopefully you'll appreciate what I mean.
    John: I'm certain the answers we need cannot come from the Standard Model. Questions like "Why mₑ = 511keV" are precisely the sort that can't be answered from within the SM, by definition. If you mean you want certain features of the standard model explained, then I agree. Thats one of the principal goals of BSM model building.

    I think string theory is exactly as radical as required for what it needs to do. I obviously appreciate a healthy skeptical attitude, and I might be wrong, but I think there are some very strong signs pointing to its physical relevance. Already the completeness, robustness and richness of the picture is extremely compelling, and the kind of thing that no humans could ever just come up with, as opposed to Nature herself. But what really seems to cement its inevitable role is how deeply linked all of it is with quantum field theory. The famous holographic duality is the most spectacular example, but there are other connections, some less understood. So exactly like you said, in a sense we don't need to find some new generalization, because the would-be generalization was encoded in the framework we already use. String and field theory research are really going hand-in-hand now, driving each other forward.

    I totally agree, that we must understand QFT more deeply, that many people are asking the wrong questions, and that field theory is still poorly understood (both by science collectively, and even more so by lots of individual physicists too). Some of the most important questions in HEP are to understand where the qualitative properties of quantum Yang-Mills theory come from (if you like, Yang-Mills-Dirac-Higgs-Einstein theory) and thats exactly where string theory's most important contributions are. I encourage you to think about any other possibilities you come up with. But by now we know very well that it is almost impossibly difficult it is to come up with a word-level idea that can be translated into consistent mathematics with the needed properties.

    Overall, I think there is a very strong case that it would be completely crazy if this random math structure just happened to exist with all these correct properties to describe quantum gravity and everything else, black holes evaporating, topology change, emergent spacetime, holographically encoding quantum field theory for no reason, etc, etc. So I try to encourage people who might care to see for themselves why some of us are so excited about it and don't necessarily take someone's word who tells you not to be interested.

    John Duffield
    Thanks for getting back to me at length Cliff. Yes, I agree that the answers aren't going to come from the Standard Model per se, but I do think other theories/fields can contribute, and the BSM guys are missing some good clues. I don't have a big problem with string theory myself. Whilst I don't like to hear "string theory is the only game in town", I don't see a huge difference between vibrating strings and wave harmonics. It's like you start with a toy-model lattice, simplify it to a 2D grid, and then QFT is dealing with the cells while string theory is dealing with the lattice lines. I'm not a fan of holographic duality or evaporating black holes though. IMHO those clues I mentioned offer some guidance, and they don't seem to lead that way. But I'd say they are in line with Yang-Mills-Dirac-Higgs-Einstein theory which I think can be put into words, at least in part, in outline.

    To give you a flavour of all this, take a look at Minkowski’s Space and Time and note this: “In the description of the field caused by the electron itself, then it will appear that the division of the field into electric and magnetic forces is a relative one with respect to the time-axis assumed; the two forces considered together can most vividly be described by a certain analogy to the force-screw in mechanics; the analogy is, however, imperfect” . Then see section 11.10 of John Jackson’s Classical Electrodynamics and note "one should properly speak of the electromagnetic field Fuv rather than E or B separately". An electric field is usually drawn with radial field lines, a magnetic field is usually drawn with concentric field lines. But E and B aren't fields, they denote the forces that result from the interaction between electromagnetic fields. And to visualize the electron's field, you combine the radial and concentric lines. Like this. It kind of "fits" with gravitomagnetism, Maxwell's Theory of Molecular Vortices, optical vortices, electron diffraction, the Einstein-de Haas effect, Wheeler's fumblings towards a geon, Baldomir&Hammond's Geometry of Electromagnetic Systems, and the Dirac spinor. Especially since counter-rotating vortices attract, and co-rotating vortices repel. A cyclone is a vortex. If you could set down two cyclones next to one another they’d move linearly apart. If you could set down a cyclone near to an anticyclone, they’d move together. And if you could hurl the cyclone past the anticyclone, they’d swirl around one another too, like electrons and positrons do in positronium. A cyclone has intrinsic spin. So does an anticyclone. That’s what makes it what it is. Cancel one spin with the opposite spin, and all you’ve got is wind. An electron has intrinsic spin too. So does a positron. Cancel one spin with the opposite spin via electron-positron annihilation, and all you’ve got is light. Whilst the flat depiction doesn't seem to fit with Dirac's belt, the spindle-sphere torus does. It fits with TQFT too. Note that Thomson and Tait coined the term "spherical harmonics". And that in atomic orbitals, "electrons exist as standing waves". They exist as standing waves full stop. And for a cherry on top, you know that Planck length is l=√(ћG/c³). Replace √(ћG) with 4πn where n is a suitable value. You've still got your Planck length. But now set n to 1, and work out 4πn/√(c³). There's a binding energy adjustment, but it's g-factor slight, and you can recognise the electron Compton wavelength straight away. 

    What are the chances of all that being completely crazy? 
    Cliff said, " I would definitely answer "yes", even if it waits to be completed by other important insights – some knowable and some perhaps unknowable" So string theory depends on insights which are unknowable, eh? Don't you think that " I would definitely answer "yes", even if it waits to be completed by other important insights – some knowable and some perhaps unknowable" is perhaps a very long way of saying, "no"?

    By the way, you speak of "explanatory power". That's good to hear. Tell us about how string theory [not SUSY alone] explains dark energy and dark matter and the hierarchy problem. Does it also explain the quantization of money, in quanta of US$3 x 10^6 ?

    Absolutely not. I guess you don't know that there must inevitably be unknowable properties of any consistent formal system. Kind of important fact in this business. Nor have you appreciated the significant outstanding questions within standard quantum field theory. Don't misunderstand me, all of the machinery of quantum field theory and string theory works but more and more aspects are being learned about. You don't ever get to know everything for free. Not in classical physics and not in string theory.

    String theory is just like any other physical theory in that before you make predictions you first need to specify a configuration of the physical ingredients. I don't know what the exact high-energy dynamics of this universe are, but I know that string theory has particular classes of possibilities relating that effective field theory information to specific configurations of stringy objects. Any proposed configuration leads to specific predictions and nontrivial conditions on the effective field theory we see. Vacuum energy is just one physical quantity among many to be related.

    You may want to read, e.g. http://nlab.mathforge.org/nlab/show/string+theory+FAQ

    " I don't know what the exact high-energy dynamics of this universe are, but I know that string theory has particular classes of possibilities relating that effective field theory information to specific configurations of stringy objects. Any proposed configuration leads to specific predictions and nontrivial conditions on the effective field theory we see. Vacuum energy is just one physical quantity among many to be related."

    That reads like it was written by a committee. One imagines the following conversation:
    ANXIOUS FATHER: WHAT! PREGNANT??!!
    TEENAGED DAUGHTER: I don't know what the exact high-energy dynamics of this universe are, but I know that pregnancy is one of many classes of possibilities relating inadequate parental guidance to specific configurations of the reproductive tract. Any proposed configuration leads to specific predictions and nontrivial conditions on the shape of a given teenaged girl we see. Pregnancy is just one physical condition among many to be related.

    @Cliff

    I am hesitant to speak for others, but for me, saying "No" to question 6 is not a statement that I know of a better alternative, and so disbelieve ST, but rather that ST itself has to show me something more than an anthropic multiverse before I'll call it a candidate theory of anything, or feel comfortable calling it a step in the right direction, because I have no idea what direction ST is a step in (aside from being consistent, and I agree wholeheartedly that it's a step in the right direction to be able to construct a consistent theory, but I don't jump from this to "it's a step toward the final theory" because it could easily be on completely the wrong track). Perhaps the landscape is the true explanation, but I won't give up looking for alternatives and accept that without a much better argument than a lack of known viable alternatives.

    Here's a relevant comic from SMBC, one of my favorites: http://www.smbc-comics.com/index.php?db=comics&id=2866

    I agree that ST is a very deep, impressive hole and that there are no other comparable ones yet, but I don't see how it follows from that that ST must be digging in the right direction.

    Anon, I totally understand the attitude. As I alluded to in my answer to John above, the motivations for string theory go way beyond just being a consistent possibility, despite how unique that property is.

    Its really frustrating how widespread this myth is that string theory offers only anthropic explanations. Thats a meme almost entirely propagated by Peter Woit and similar people. He likes to pretend that nothing new ever happens and that there is no content to any string theory research because he desperately wants to dismiss all of it and declare victory, and he wants to convince his audience not to learn more about it. The reality is that string theory is still incredibly active, vibrant and relevant for physics fundamental physics going forward. If you talk to knowledgable theorists or do some reading you can learn much more about the actual relationships that are continually being established between concepts and phenomena in field theory and string theory.

    Regarding anthropics, there is a chance that some of the questions we face today may have anthropic explanations, and to investigate that as a possibility is not the same as throwing up your hands and "giving up" as people like Woit dishonestly claim. On the contrary, it's just one possibility that must be considered among many. We can't justify dismissing it simply because it might be inconvenient for humans. Its true that some signs can be interpreted as pointing in that direction, and a lot of research has explored the possibility, but if anthropics turn out to be right that would still represent a relatively tiny part of the knowledge wed have gained about how nature works.

    Cliff said "It sounds like all your readers think the LHC particle physicists can just go home, since their work is apparently done. ;]"

    Showing that there is no new physics below a few TeV is as important as finding something and is in fact a harder task. So the LHC experimentalists do have important work to do. How we reward a null result is something we need to think of as society.

    Since nothing has been found so far many people have started believing that we are on the wrong track with SUSY and other solutions of the hierarchy problem that cleanly solve it by requiring new physics at weak to TeV scale. Faith on these things seem to have moved in two directions -- one such as Cliff's isn't diluted on them, but they are now willing to accept fine-tuning of SUSY models that spoils the cleanness of the hierarchy solution, while others are willing to accept this situation in the standard model itself without need for SUSY.

    Cliff -- at some point if the LHC or future colliders continue to not find new physics would you move away from your answer 1A -- at which energy scale of null result would you do this?

    The problem is while one might think the posterior probability for Susy diminishes as parameter space is eaten up, in a sense it will always be the most likely solution just around the corner. That's because the apparent choice is between finetuning around the .1% level and greater vs tuning through some 16 orders of magnitude.

    What's needed is a better theoretical idea than Susy to stabilize the electroweak scale. If such a thing was invented tomorrow you would see the belief in Susy drop like a stone.

    The argument that SUSY is round the corner will lose credibility (things are moving in this direction already) if no evidence for it is found by the LHC. This is itself a big blow. I think what is great about 'SUSY as a solution to the weak scale hierarchy problem' is that it is an experimentally FALSIFIABLE theory. I think at some point there will be (has to be) a consensus that it was falsified.

    dorigo
    Not entirely true Anony. Split SUSY may live on after the LHC and even higher-energy colliders, because there is no definite upper limit on the mass of the SUSY particles you can work with.
    Cheers,
    T.
    T,
    Split SUSY does not solve the hierarchy problem as it is fine-tuned. In fact it is very highly fine-tuned as per papers of Nima etc. Its purpose is to continue to have unification of gauge couplings and maybe also continue to have lowest mass SUSY particle stabilized by R-parity as dark matter. SUSY as a solution to the hierarchy problem can be falsified.

    Hi, above all, this is a poll on the audience! Of course the answers would have been different at SUSY2013.
    The question that is relevant for me is: should we be looking for BSM theories at the LHC and future colliders? Since the answer is trivial, the next question should be: how? The best chance is looking for not yet excluded well understood models for which there is a good discovery potential. Unfortunately the LHC gave us no hints, but I would have asked which BSM searches should have priority at the LHC and future colliders. Say, 3 out of a list. Here, I would bet on SUSY making the list. Sure, this is also subjective. By the way, what humans believed in, except maybe in themselves, didint help them that much...