
Ultra-rare kaon decay could lead to evidence of new physics - bookofjoe
https://phys.org/news/2019-09-ultra-rare-kaon-evidence-physics.html
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gus_massa
It's a pity that the Feynman diagram at the top is not the diagram of the
disintegration they are discussing. IIUC this are the correct diagram
[https://www.caen.it/na62-spots-two-potential-instances-of-
ra...](https://www.caen.it/na62-spots-two-potential-instances-of-rare-
particle-decay/) .

The Kaon disintegrates into a Pion, a neutrino and an antineutrino. This
process is rare because you need two virtual Z or W particles in the
intermediate steps of the decay.

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platz
> This combined result is compatible with the Standard Model prediction

Ok they haven't found anything yet..

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asplake
Right. Read the article twice and I still don’t know what they mean by “new
physics”.

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at_a_remove
It's more that they've set up a marker that says "We're getting good at
measuring the K+ decay, which is super-rare, and we are trying to establish a
good frequency for it. Anything new physics proposed has to be within a
certain error range of this result." It's more of a way to quickly rule out
"new physics" models that do not pass the test than anything else.

In some sense, many of these measurements are ways to provide more points in
some kind of line-fitting we have going on. "Sure, your new idea waves away
dark matter buuuuuut there's this little matter of its predicted K+ decays.
They would be way off. Either come up with a way to explain _that_ or try
again."

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Sharlin
(2019)

