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Science Technology

Scientists To Hunt For Supersymmetric Particle In LHC 89

Posted by samzenpus from the back-to-science dept.
An anonymous reader notes this article about the upcoming restart of the LHC. "A senior researcher at the Large Hadron Collider says a new particle could be detected this year that is even more exciting than the Higgs boson. The accelerator is due to come back online in March after an upgrade that has given it a big boost in energy. This could force the first so-called supersymmetric particle to appear in the machine, with the most likely candidate being the gluino. Its detection would give scientists direct pointers to "dark matter". And that would be a big opening into some of the remaining mysteries of the universe. 'It could be as early as this year. Summer may be a bit hard but late summer maybe, if we're really lucky,' said Prof Beate Heinemann, who is a spokeswoman for the Atlas experiment, one of the big particle detectors at the LHC. 'We hope that we're just now at this threshold that we're finding another world, like antimatter for instance. We found antimatter in the beginning of the last century. Maybe we'll find now supersymmetric matter.'"
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Scientists To Hunt For Supersymmetric Particle In LHC More

Scientists To Hunt For Supersymmetric Particle In LHC

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  • The upgrade they completed DOUBLES the energy!

    • Re:2x power (Score:5, Funny)

      by fisted ( 2295862 ) on Sunday February 15, 2015 @11:47AM (#49060027)
      Oh noes. So we're all gonna die, like, twice!

    • Re: (Score:1)

      by Drexus ( 826859 )
      And at which point, all past experiments will want another shot at confirming results — drawing a reference point for new experiments of tomorrow.
    • Some people are worrying [inquisitr.com] about doubling the LHC power.

    • Actually 13/8 times the energy (Score:5, Informative)

      by Roger W Moore ( 538166 ) on Sunday February 15, 2015 @02:18PM (#49060835) Journal
      The centre of mass energy is actually going from 8 to 13 TeV so it is not a doubling of the energy. However we are increasing the luminosity (number of protons in the beam) too so we will probably have at least twice the reach in energy that we did before. While the article makes it sound like something new looking for Supersymmetry (SUSY) is something we have been searching for since the start of the LHC.

      SUSY is the leading candidate theory to explain why the higgs is so much lower in energy that the energy scale at which gravity becomes important: the Planck scale. While there are good arguments to suppose that SUSY is within range of the LHC energy I would put about as much store in a prediction of which SUSY particle will be discovered first as I would in a 14 day weather forecast: there is some science that goes into it but there are so many unknowns that the prediction is likely to be junk. Worse, while we can be pretty certain that there will be some sort of weather in 14 days there is no guarantee that there is a lightest SUSY particle: SUSY might not exist in nature although this itself would raise some interesting questions.

      • True.
        But, if we are going to discover a SUSY particle in the first months after turning on, it is indeed very likely to be the gluino. Just because the probability of creating it, if it is within kinematical reach, will be large, compared to many other SUSY particles. All weakly produced particles will take more data to get hold of because they are rarer. In addition, in most models, the gluino decays give rise to spectacular collisions, that are relatively easy to distinnguish from known backgrounds.

        • ...and what about squarks? These are strongly coupled and there are some arguments to suggest that the stop squark is most likely to have the lowest mass.

          • Yes, the stop (and sbottom) squark is a prime target too.
            But it will come again a little later than the gluino. The reason is that we have excluded the gluino in most scenarios already wel beyond 1.2TeV, while the stop squark is unlimited above ~700GeV (and that's assuming ideal decays).
            Now, with the increase in energy, the heavier is the particle, the higher the increase in production probability. This is visualised in the following (M_X being the "mass" of the produced system, in this case twice the gluin

            • But it will come again a little later than the gluino.

              All these arguments are reasons why it is easier to see stops than gluinos which I'm already aware of. However what you are also assuming here is that the gluino mass is comparable to the squark masses. Is there any justification for that because I've not seen it e.g. if the gluino mass is 3 times that of the squarks it will not be seen first.

              Unless there is an argument to say why this is disfavoured you are drawing unwarranted conclusions based on detector sensitivities. It doesn't matter how much more

              • I referred to the current limits (~1.2TeV for gluino versus 700GeV for stop), which is more or less corresponding to a couple of events on a small background - for both gluino and stop searches at their high-mass extremes.
                Production probability (cross section) plot for 8TeV can be seen here:
                http://inspirehep.net/record/1... [inspirehep.net]
                Couldn't find a 13TeV version quickly; but the trends are the same: much higher probability for gluino paris (~g~g in red) than for stop pairs (blue curve).
                Now, when we move from 8TeV to

                • You are completely missing the point. Consider two scenarios: (a) a 1.25 TeV gluino and a 1 TeV stop and (b) a 5 TeV gluino and a 750 GeV stop. Which of these two possible SUSY models is more likely? (a) or (b)? If the answer is (as I suspect) that they are both roughly equally likely then you are just as likely to see the stop quark first as you are to see a gluino first: in (a) you see the gluino and in (b) you see the stop first.

                  If you want to say that seeing a gluino is more likely then you have to b

                  • For the same reasons the stop is expected light (naturalness, i.e. SUSY as a solution to the hierarchy problem), also the gluino is expected light. What is light? Some put it at 400GeV for the stop, and 1.5 TeV for the gluino. But it's a bit of a subjective point. So if you like natural SUSY, you expect the gluino to be around the corner, and the stop to be within reach, but probably decaying softly and therefore having escaped detection so far. How likely is such a scenario? There is no good metrci for the

                    • Therefore I prefer to look at it experimentally, i.e. wrt our current limits. If the gluino and stop are just beyond our current limits, then, according to my previous posts (which apparenntly completely missed the point...) the gluino will jump in our face

                      How is making an arbitrary choice that stop and gluino are both just beyond the current limits "looking at it experimentally"? What's to prevent stop being just beyond our detection range with the gluino being far above it? The argument for a light stop is that the top has a large correction to the Higgs mass due to its strong coupling: I'm not aware of any such argument for the gluon since it is massless. Natural SUSY does not place any hard limits on the upper bounds: things just get less natural as the

                    • The gluino plays a similar naturalness role as the stop, at 2-loop level. Now you are aware, though I made that point in my previous post too.

                      Just beyond the limits is not an arbitrary choice. Given our current limits already, naturalness points to these masses being as low as possible.

                    • The gluino plays a similar naturalness role as the stop, at 2-loop level.

                      Do you have a paper to back that up? It seems very surprising that a 2-loop level effect would have the same constraints as something at the tree level.

                      Just beyond the limits is not an arbitrary choice. Given our current limits already, naturalness points to these masses being as low as possible.

                      Not quite. Given our current understanding it would appear more natural to have SUSY at a lower mass scale but if we find SUSY at 10TeV all that means is that SUSY is perhaps less natural than it could have been. It's like tossing a coin: how many heads in a row do you need to get before you conclude that the coin is weighted? You can draw an arbitrary lin

                    • A classic by now on SUSY naturalness related to LHC: http://arxiv.org/abs/1110.6926 [arxiv.org]
                      See Section II.

  • I hope there'll be no supersymmetry (Score:1)

    by Anonymous Coward

    No matter what virtues it may have, a theory that doubles the number of elementary particles is a gross violation of Ockham's razor. Well, maybe that's the way the world is made up. I just hope it isn't.

    • Re: (Score:1)

      by Anonymous Coward

      The question is, do you have a simpler explanation? If not (and no, I'm not convinced that 13 dimensional vibrating strings is simpler) then Ockham's razor still holds.

      • What could happen if they discovered the Voldemortino?

      • Re: (Score:2)

        by hweimer ( 709734 )

        The question is, do you have a simpler explanation?

        Er, stick to the Standard Model since there is no experimental observation to the contrary? (Okay, there are neutrino oscillations, but it is possible to fix this without supersymmetry or extra dimensions.)

        • Well theres neutrino oscillations, g-2 of the muon, baryogenisis, dark matter, dark energy and inflation to name a few.

          Then there is the hierarchy problem and flavour problems which aren't experimental observations so you might not want to count them and thats not even touching the problem of trying to get a consistent theory for the standard model and gravity together.

          • Re: (Score:2)

            by hweimer ( 709734 )

            Other than muon g-2 (which might or might not be there), none of the things you mention actually contradict the standard model because it simply makes no statement about them. It's way too early to send the standard model down the drain because the alternatives either contain more speculative physics than known physics or are conceptually elegant but still wrong (see SU(5)).

  • LHC upgrade (Score:1, Funny)

    by Anonymous Coward

    I hope it does not include systemd

  • Hunt for Particle in LHC (Score:5, Funny)

    by PPH ( 736903 ) on Sunday February 15, 2015 @01:19PM (#49060495)

    Just turn it on its side and smack it a couple of times. That's how I get loose bits out of machinery.

  • We found it ...zup...
    -end of transmission from earth-

  • Supersymmetry already has strong constraints (Score:5, Informative)

    by hweimer ( 709734 ) on Sunday February 15, 2015 @02:27PM (#49060881) Homepage

    The observation that the electron electric dipole moment is less than 10^-29 e cm (as measured by the ACME experiment [arxiv.org] in 2013) already places strong constraints on supersymmetric partner masses, making it rather unlikely that the upgraded LHC will see anything.

    • IIRC there are other results that further limit the space available for SUSY, minimal or otherwise. But just like string theory, its supporters refuse to go away.

  • IANAPP, but I thought that the lack of observed proton decay had largely invalidated supersymmetry.

    I mean, "yea science" and all, but I suppose am I missing something?

    • we've only looked for proton decay on the order of 10^34 years half-life, if it's larger there is no extant experiment that would see it.

    • You only need one extra symmetry (so-called R parity) to protext the proton from decay. Such a symmetry is not far-fetched, and arises in some GUT models even dynamically. Imposing this R parity yields also automatically a stable lightest supersymmetric particle, and it turns out that that can be a really plausible dark-matter candidate. This said, studies also go on about models where this R parity is not conserved, still keeping the proton's lifetime within the stringent experimental bounds.

  • Specifically finding SUSY would be great for the people who predicted it. From the point of view of particle physics as a whole, the goal is seeing some physics not covered by the standard model. In any case unless you can write papers on the topic, it's useless to speculate what will be found. Since the accelerator already exists we don't need any hype about it.

    However, if even this energy upgrade doesn't bring signals beyond the standard model, it will be very hard to ask for many billions of USD to bu

  • I'm pretty sure that you guys are making all this up. It looks like cern geeks keep inventing theoretical particles, then search for them, find something that almost fits, then theorizes that another particle must exist, look for that until you find something that almost fits, then look for another particle etc. etc. etc.
    It's like those astrophysicists. They have no idea either and keep making up hypotheses, backed up by arcane invented maths using as many dimensions as they can so they can postulate weirde

    • I'm pretty sure that you guys are making all this up.

      You admit you are not a physicist. That means you admit you do not know what your are talking about.

      It looks like cern geeks keep inventing theoretical particles, then search for them, find something that almost fits, then theorizes that another particle must exist, look for that until you find something that almost fits, then look for another particle etc. etc. etc.

      Not just CERN "geeks" but scientists from all over the world, looking for patterns in the way the universe is constructed. Patterns are useful, because they allow us to distill vast amounts of knowledge into a much smaller number of concepts. It's no secret that scientists try to find patterns that fit observations, and then try to extend their applicability to other potential observations, with the goal of f

  • Particle physics did an excellent job building a multidisciplinary, international, scientific workforce. As a field, they are largely independent of the world of 12-36 month grants and frequent peer reviewed publications the rest of us live in. More scientific fields should look to particle physics for guidance on self-organization and priority setting.

    However, in the process, particle physics has separated itself from general physics. Outside of some cosmologists, there are not many other physicists who

  • I'm sorry, but all *uino are reserved for embedded controller related product names.

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