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I SUSY and GUTs all but eliminated by latest ACME experiment

  1. Oct 18, 2018 #1
    I'm surprised no one has posted about this yet, so I guess I'll take it upon myself to post the link, even though I have no real expertise on the subject. The ACME collaboration had the results of their latest measurement of the electron's EDM published in Nature today. They place an upper limit of 9.4X10-29 e cm, an order of magnitude improvement over the previous measurement. According to the chart below, this value eliminates many BSM models. I've also included a couple of pedagogical videos from the ACME group. RIP 'naturalness'.


    Last edited: Oct 18, 2018
  2. jcsd
  3. Oct 18, 2018 #2


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    The relevant constraint analysis which that chart is based on is :

    It should be noted that the subclass of models that are being considered and ruled out are rather extreme. So significant caveats and loopholes exist in the general case for all models considered. The plots in the original paper are more indicative of the reach of this experiment. Still this experiment quite significantly constrains the relevant theory spaces for model builders.
  4. Oct 18, 2018 #3

    Vanadium 50

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    Which makes the title highly misleading.
  5. Oct 26, 2018 #4

    Buzz Bloom

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    I am puzzled by the upper limit value of 9.4X10-29 e cm.
    Within the Standard Model of elementary particle physics, such a dipole is predicted to be non-zero but very small, at most 10−38 e·cm.

    If I am understanding correctly what I am reading, the new upper limit value is 10 orders of magnitudes larger than the upper limit quoted in Wikipedia. Now I know that Wikipedia's reputation in the PF is not on a par with authoritative journals like Nature, but this extreme difference is quite puzzling.
  6. Oct 26, 2018 #5

    George Jones

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    The above is an experimental observation

    This a standard model theoretical prediction. Some Beyond the Standard Model theories make larger predictions.
  7. Oct 26, 2018 #6
    I goofed on the upper limit: I quoted the old one--the new one is actually an order of magnitude smaller (by 'smaller' I mean that it's approximately one-tenth the value that I quoted). You can find it in the linked paper. For some reason I'm not able to edit my original post. Also, if I could, I would retitle the thread "Natural SUSY all but eliminated..." to make it more accurate.
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