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The Rise and Fall of Supersymmetry 138

Ethan Siegel at the StartsWithABang blog writes: "Have you ever wondered why the masses of the fundamental particles have the small values that they do, compared to, say, the Planck scale? Whether the fundamental forces all unify at some high energy? And whether there's a natural, compelling particle candidate for dark matter? Well, in theory supersymmetry (or SUSY, for short) could have solve all three of these problems. In fact, if it solves the first one alone, there will be definitive experimental signatures for it at the Large Hadron Collider. Well, the LHC has completed its first run, and found nothing. What does this mean for theoretical physics, for SUSY in particular, and what are the implications for string theory? A very clear explanation is given here; it might be time to start hammering in those coffin nails."
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The Rise and Fall of Supersymmetry

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  • by flaming error ( 1041742 ) on Tuesday March 04, 2014 @11:28PM (#46404767) Journal

    I'll try. Supersymmetry predicted the existence of subatomic particles which the LHC would detect. The LHC hasn't detected them.

  • by dreamchaser ( 49529 ) on Tuesday March 04, 2014 @11:31PM (#46404791) Homepage Journal

    I don't think there is one. Simply but probably poorly put, supersymmetry postulates that each particle that we know of and have observed has a heavier 'super-symmetric' partner particle. The significance of this is that if true it explains a whole bunch of how the observed Universe works. If it is not true it's almost as exciting really, at least to me, because it means there are some big missing pieces to our current models and a lot of new and exciting work will need to be done.

    The short version of the article is that the LHC should have detected supersymmetric particles by now. There's still a slight chance that the next run will, but the energies that fit the current theories are running out. If they are not detected soon physicists might just have to move on to new theoretical models. For one thing, string theory will probably need to be scrapped.

  • by negablade ( 2745981 ) on Wednesday March 05, 2014 @06:54AM (#46406527)

    Just because it's ridiculously hard to prove doesn't mean that it's false. For example, most physists believe gravity needs a force carrier which they've called a "graviton", the same way light (electromagnetic radiation) consists of photons. That theory is 80 years old and still totally unproven but as long as nobody has a good competing theory we still kind of assume that's how it works.

    Gravity waves have already been proven to exist. The 1993 Nobel Prize in physics was awarded for the study of the Hulse-Taylor binary pulsar that showed indirect confirmation of the existence of gravity waves [].

    Not that we're not trying to look for gravitational waves and other clues, but most of it is so far off the scale of what we can experimentally detect that it'll probably still be unproven in a thousand years.

    Gravity wave detection is expected within the next 20 years from the LIGO programme [], [] and []. It won't require a thousand years, nor is it beyond existing technology. LIGO is already taking measurements in the US, at Hanford and Livingston, and advanced LIGO will increase the sensitivity of the LIGO interferometers by a an order of magnitude, and is expected to increase detection rates from a few per year to 100s per year by increasing the detection volume a thousand fold. If advanced LIGO doesn't detect anything, then it will be time to review the theory.

    (I worked for ~6 years at the University of Western Australia in the physics department in collaboration with the Australian LIGO research group)

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