
NA62 spots two potential instances of rare particle decay - lelf
https://home.cern/news/news/physics/na62-spots-two-potential-instances-rare-particle-decay
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JohnDeHope
It seems like every article like this can be summarized as: this experiment or
analysis could indicate physics beyond the standard model, we ran the
experiment or analysis, and we found nothing unexpected. At this point I find
myself asking what the ramifications would be if the standard model is correct
and is all there is. It seems less worthwhile to wonder about alternatives to
the standard model. Please correct my thinking.

~~~
planck01
It can't be complete and all there is, because it doesn't explain everything
we know exists. To simply quote wikipedia:

"It does not fully explain baryon asymmetry, incorporate the full theory of
gravitation as described by general relativity, or account for the
accelerating expansion of the Universe as possibly described by dark energy.
The model does not contain any viable dark matter particle that possesses all
of the required properties deduced from observational cosmology. It also does
not incorporate neutrino oscillations and their non-zero masses."

~~~
CharlesColeman
> It can't be complete and all there is, because it doesn't explain everything
> we know exists.

However, it could very well be that a true scientific theory that explains
those things is beyond our experimental verification, and the Standard Model
(or something not much beyond it) will fit all particle accelerator
observations made in the next thousand years or more.

~~~
nine_k
Fortunately we have astronomic events. No Earth-based experiment could emit
gravitational waves strong enough to detect; good thing the Universe has
plenty of black holes, and some of them merge.

~~~
CharlesColeman
> Fortunately we have astronomic events.

That may help with some things, though it's not at all clear it's sufficient
to verify a true theory that "explain[s] everything we know exists." It brings
to mind the graviton, which I've read would be practically impossible to
detect: you could detect one graviton every ten years with a Jupiter-mass
detector placed very close to a neutron star, but the shielding needed to
exclude the noise would cause it to collapse into a black hole.

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317070
Why is this result interesting? All of the particles involved are pretty
exotic, and this is still fitting the Standard model. Can someone enlighten
me?

~~~
evanb
This kind of decay requires an overall neutral current that changes the
strange quark to a down quark. No such current exists at tree level in the
Standard Model---instead, strange has to turn into an up-type quark and from
there into a down. So, anything from the SM that contributes to this process
necessarily involves loops and has no large SM backgrounds. That makes it a
very sensitive probe for searching for new physics. Everything seems
consistent with the SM but that need not have been---certain kinds of new
physics would have stood out in this decay channel. So, while it's not a
discovery of a new particle, for example, it is a result that can tightly
constrain conjectures.

