SUSY and GUTs all but eliminated by latest ACME experiment

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Discussion Overview

The discussion centers around the recent results from the ACME collaboration regarding the electron's electric dipole moment (EDM) and its implications for beyond the Standard Model (BSM) theories, particularly supersymmetry (SUSY) and grand unified theories (GUTs). Participants explore the significance of the new upper limit measurement and its impact on various theoretical models.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant highlights the new upper limit of 9.4X10-29 e cm as a significant improvement over previous measurements, suggesting it eliminates many BSM models.
  • Another participant provides a link to a constraint analysis, noting that the models being ruled out are extreme and that significant caveats exist regarding the general applicability of the results.
  • A different participant challenges the title of the thread, arguing it is misleading due to the extreme nature of the models considered.
  • Concerns are raised about the discrepancy between the new upper limit and the Standard Model prediction, which suggests a much smaller dipole moment, leading to confusion regarding the implications of the new measurement.
  • One participant clarifies that the new upper limit is indeed larger than the Standard Model prediction but acknowledges that some BSM theories predict larger values.
  • A participant admits to initially misquoting the upper limit and corrects themselves, suggesting a more accurate title for the thread to reflect the findings better.

Areas of Agreement / Disagreement

Participants express differing views on the implications of the new measurement, with some arguing it significantly constrains theoretical models while others emphasize the extreme nature of the models considered and the potential for loopholes. The discussion remains unresolved regarding the overall impact on SUSY and GUTs.

Contextual Notes

Limitations include the dependence on the definitions of the models being discussed and the unresolved nature of the implications of the new upper limit measurement in relation to existing theoretical predictions.

MrRobotoToo
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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'.

PW-2013-11-147-Johnston-edm-second.jpg


 

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The relevant constraint analysis which that chart is based on is :
https://arxiv.org/abs/1612.08090

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.
 
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Haelfix said:
It should be noted that the subclass of models that are being considered and ruled out are rather extreme

Which makes the title highly misleading.
 
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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.
 
Buzz Bloom said:
If I am understanding correctly what I am reading, the new upper limit value is 10 orders of magnitudes larger

The above is an experimental observation

Buzz Bloom said:
than the upper limit quoted in Wikipedia

This a standard model theoretical prediction. Some Beyond the Standard Model theories make larger predictions.
 
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Buzz Bloom said:
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.
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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