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Science

Supersymmetry Theory Dealt a Blow 143

Posted by samzenpus
from the state-of-things dept.
Dupple writes in with some news from the team at the Large Hadron Collider. "Researchers at the Large Hadron Collider have detected one of the rarest particle decays seen in Nature. The finding deals a significant blow to the theory of physics known as supersymmetry. Many researchers had hoped the LHC would have confirmed this by now. Supersymmetry, or SUSY, has gained popularity as a way to explain some of the inconsistencies in the traditional theory of subatomic physics known as the Standard Model. The new observation, reported at the Hadron Collider Physics conference in Kyoto, is not consistent with many of the most likely models of SUSY. Prof Chris Parke, who is the spokesperson for the UK Participation in the LHCb experiment, told BBC News: 'Supersymmetry may not be dead but these latest results have certainly put it into hospital.'"
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Supersymmetry Theory Dealt a Blow

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  • by Anonymous Coward

    First it was the Novell acquisition, then the Microsoft licensing... when will it end?

  • Bad summary (Score:5, Informative)

    by AdamHaun (43173) on Monday November 12, 2012 @05:48PM (#41961219) Journal

    The summary, like the article, jumps straight into "OMG CONFLICT" without bothering to tell us what's going on. From later in the article:

    Researchers at the LHCb detector have dealt a serious blow to [supersymmetry]. They have measured the decay between a particle known as a Bs Meson into two particles known as muons. It is the first time that this decay has been observed and the team has calculated that for every billion times that the Bs Meson decays it only decays in this way three times. If superparticles were to exist the decay would happen far more often. This test is one of the "golden" tests for supersymmetry and it is one that on the face of it this hugely popular theory among physicists has failed. ...

    The results are in fact completely in line with what one would expect from the Standard Model. There is already concern that the LHCb's sister detectors might have expected to have detected superparticles by now, yet none have been found so far.

    But it sounds like this is only a problem for some variants of supersymmetry:

    "If new physics exists, then it is hiding very well behind the Standard Model," commented Cambridge physicist Dr Marc-Olivier Bettler, a member of the analysis team. The result does not rule out the possibility that super particles exist. But according to Prof Parkes, "they are running out of places to hide". Supporters of supersymmetry, however, such as Prof John Ellis of King's College London said that the observation is "quite consistent with supersymmetry". "In fact," he said "(it) was actually expected in (some) supersymmetric models. I certainly won't lose any sleep over the result."

    • by Carewolf (581105)

      But it sounds like this is only a problem for some variants of supersymmetry:

      Yes and no. You can always change the theory to adapt, but if you continue to do that, at some point it stops being science, see http://www.stephenjaygould.org/ctrl/popper_falsification.html [stephenjaygould.org] . SoSY has been counterproven by several different experiments now, they are slowly but steadily running out of all the nice versions, and they have never had any positive confirmation. All it relied on was that it could be nice model if it wa

      • Re:Bad summary (Score:4, Informative)

        by Pseudonym (62607) on Monday November 12, 2012 @07:13PM (#41961969)

        SUSY is not a theory which is altered every time a new relevant discovery is made. It's a (quite large) family of theories, some of which are ruled out every time a new relevant discovery is made.

      • Re:Bad summary (Score:5, Informative)

        by Roger W Moore (538166) on Monday November 12, 2012 @07:32PM (#41962143) Journal

        But it sounds like this is only a problem for some variants of supersymmetry:

        Yes and no.

        Actually just 'yes'. SUSY is essentially a mirror image of the Standard Model about which we know very little indeed (only limitations on it). Hence the best models assume nothing which is not expressly forbidden and so we end up with ~120 free parameters vs the 25 free parameters for the Standard Model which we have measured and so excluded many of the possibilities. For example the we set the mass of a photon and a gluon to zero in the Standard Model because we have no evidence that they have a mass and the Lagrangian requires zero mass for it to have the correct symmetries. However in fact all we can do is put an upper limit on the mass from experiment: this is a better example of the illustration you are trying to make.

        The Standard Model already heavily suppresses Bs->mumu decay all this has shown is that SUSY, if it exists, likewise heavily suppresses it. This is a very interesting result but, far from falsifying SUSY, it just means that SUSY is perhaps more like the Standard Model than we think it needs to be. Since we have no clue about how Supersymmetry is broken this is not too surprising...so I'd say it's very interesting and certainly constrains SUSY but it is by no means its death knell. Indeed arguments about excluding phase space and so therefore making a theory less probably are somewhat akin to arguing that choosing the numbers 1,2,3,4,5,6 in a lottery is stupid because they will never come up. If SUSY is there nature has chosen one set of parameters for it and, if that happens to be the last place we look it is the last place we'll find it. However if we find no hints of SUSY particles at the LHC once we run with a higher energy (March 2015) then it will start to be in trouble because at that point it becomes a less likely solution to the problem it was actually invented to explain: why is the Higgs mass so much less than the energy scale of gravity?

        • One of the unsatisfying properties of the standard model is its large number of free parameters. A replacement which has approximately five times as many doesn't seem too desirable to me. Generally, the less free parameters you have, the better. You know, with enough free parameters, you can fit an elephant.

          • by Immerman (2627577)

            I may be wrong, QM isn't my area of expertise, but I believe many of the, for example, superstring theories are attempts to "nail down" a lot of the free parameters by giving them physical meaning/making them emergent properties of the theory. In that case it's a situation of the current theory is full of ugly free parameters - but not enough of them to flex into an elegant theory consistent with observations. In which case adding a bunch of additional free parameters may actually allow you to nail them a

          • A replacement which has approximately five times as many doesn't seem too desirable to me.

            Actually I used to feel the same way - that ultimately we should have a theory with 0-1 free parameters until a colleague pointed out another possibility. Suppose you have a universe where there are many free parameters but, ultimately, the physics ends up being pretty similar regardless of their actual choice? Since then I've been a lot less hung up on the idea of free parameters despite the fact that neither scenario is applicable to SUSY!

            SUSY was invented to explain why the Higgs mass is around 126 G

      • by Rogerborg (306625)

        You can always change the theory to adapt, but if you continue to do that, at some point it stops being science

        Funny, I can't think of a better definition of science. You're applying (literal) psychobabble to physics - now that's Bad Science.

    • by oldhack (1037484)
      Comments like yours make browsing slashdot worth a damn. Unfortunately, most of yous have gone off, and I'm not one of yous.
    • by Shavano (2541114)

      But it sounds like this is only a problem for some variants of supersymmetry:

      That's a good result in itself. All the theories that can't explain what we see in LHC and be junked.

  • by Anonymous Coward on Monday November 12, 2012 @05:54PM (#41961297)

    Not to be confused with PUSY, which is still a mystery to most people here...

  • by Anonymous Coward

    From TFA:

    Supporters of supersymmetry, however, such as Prof John Ellis of King's College London said that the observation is "quite consistent with supersymmetry".

    "In fact," he said "(it) was actually expected in (some) supersymmetric models. I certainly won't lose any sleep over the result."

    It's just a flesh wound!

  • Between this and the (possible) discovery of the Higgs Boson, we may be about to launch into a new era of particle physics theory and research.

    • Lets get started... (Score:5, Informative)

      by hAckz0r (989977) on Monday November 12, 2012 @06:40PM (#41961691)
      The next big step is for them to 'prove' that what they found has more than just the mass they were expecting for the Higgs Boson. Just because something has the proper mass +/- some orders of magnitude, that was in a *very* wide ball park of their proposed Higgs, doesn't mean that it does what the Higgs is supposed to do. How they are going to actually prove that it gives all the other particles their mass, given they only know of its existence due to its decay mode (as in its already gone), is going to be one rather tough problem. We better get started...
      • by sFurbo (1361249)
        They know a bit more than the mass. They know that its spin is either 0 or 2, and they know the relative probabilities of some of the decay paths. Last I heard (this summer, right after the announcement), the proportions of the decay paths were a bit off, but more observations might put it back on track.
    • Re:Great! (Score:4, Informative)

      by mbone (558574) on Monday November 12, 2012 @08:02PM (#41962407)

      Well, assuming that something is found that is not consistent with the standard model. There is actually something from the LHC that is not consistent with the standard model, the LHCb discovery of CP violation in charm decays [blogspot.com]. This is "only" 3.5 sigma, and needs some serious theoretical work to be sure the SM prediction is even right, but as things stand it is evidence for new physics [arxiv.org].

    • by slew (2918)

      Between this and the (possible) discovery of the Higgs Boson, we may be about to launch into a new era of particle physics theory and research.

      Actually, I think it's the reverse. Between this and the (possible) discovery of the Higgs Boson, we have simply just confirmed the parts of the standard model that we think we already understand. No new physics.

      What people are actually looking for (and have found some hints/clues about like unexpected non-uniform decay paths in other experiments) are things that might suggests new physics that we don't understand at all which would launch a new era of particle physics theory and research. Some physists

  • by Swampash (1131503) on Monday November 12, 2012 @07:11PM (#41961945)

    See? Your science doesn't have all the answers.

  • by PPH (736903) on Monday November 12, 2012 @08:56PM (#41962877)

    ... wiggle all the connectors and try one more time.

  • the paper (Score:5, Informative)

    by bcrowell (177657) on Monday November 12, 2012 @09:07PM (#41962977) Homepage

    Here is the paper: https://cdsweb.cern.ch/record/1493302/files/PAPER-2012-043.pdf [cdsweb.cern.ch]

    Some blogs discussing the significance of the result:

    http://www.science20.com/quantum_diaries_survivor/lhcb_evidence_rare_decay_bs_dimuons-96311 [science20.com]

    http://motls.blogspot.com/2012/11/superstringy-compactifications.html#more [blogspot.com]

    http://profmattstrassler.com/ [profmattstrassler.com]

    Particle physics isn't my field, but neither the paper nor the blog posts seem to be interpreting it, as the BBC does, as evidence against supersymmetry.

  • The summary isn't detailed enough to bring this up, but TFA tries to equate supersymmetry with dark matter, which is emphatically wrong. The existence of dark matter is strongly supported by astronomical evidence including galaxy rotation velocities and observations of gravitational lensing, regardless of the nature of the particles that make it up. Even if this result provides evidence against supersymmetry (which doesn't seem to be the conclusion of other articles I've read, although I'm not really qualif
    • Even if this result provides evidence against supersymmetry (which doesn't seem to be the conclusion of other articles I've read, although I'm not really qualified to say), it tells us absolutely nothing about dark matter.

      Wrong. If it is evidence against supersymmetry, it tells us that dark matter is likely not composed of supersymmetric particles. Given that supersymmetric particles are one of the main hypotheses about what dark matter is composed of, I'd say it tells us very much about dark matter.

      What y

    • by Chris Burke (6130)

      TFA tries to equate supersymmetry with dark matter, which is emphatically wrong.

      No it doesn't. It equates SUSY particles with Dark Matter candidates, which is completely true.

  • So, one breast is bigger than the other?

  • I'm sure they can adjust some variables to make it fit back into their model. There is a consensus after all.
  • It was a conjecture! If you are going to define "Theory" as being supported by a preponderance of evidence, as we do when we say, "The theory of evolution." then we can't keep going around calling every damned conjecture a theory too.

    What the hell is so wrong with the word "conjecture"?

  • Susy dealt a heavy blow at the Large Hadron Collider If you can't laugh at that statement then you are dead.

I have yet to see any problem, however complicated, which, when you looked at it in the right way, did not become still more complicated. -- Poul Anderson

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