
The MiniBooNE experiment at Fermilab may have found hints of a new particle - arman0
https://www.bbc.com/news/science-environment-44370751
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panic
This blog post has a little more detail about the experiment and the physics
behind it:
[https://johncarlosbaez.wordpress.com/2018/06/02/miniboone/](https://johncarlosbaez.wordpress.com/2018/06/02/miniboone/)

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sanxiyn
The most likely explanation is an experimental error. The following quote of
the article should give you a pause:

> But there are potential problems for the sterile neutrino interpretation:
> results from other neutrino experiments, such as IceCube and Minos, show no
> evidence for a particle of this kind.

As I understand, sterile neutrino explanation not only requires you to trust
MiniBooNE, but also requires you to _distrust_ IceCube and Minos. I don't see
reasons to do so.

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ianai
That’s not what I’ve read. Iirc, it’s opening the path for new physics. Where
ever I read it, they indicated multiple experiments showing these sorts of
results. (Read up on this topic last week so I’m hazy on details.)

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dphidt
Hi, neutrino physicist here. There are indeed a handful of results that point
to a more-or-less consistent picture with sterile neutrinos, including
MiniBooNE (now updated with 2x more data), LSND, antineutrinos from nuclear
reactors, and calibrations of solar neutrino experiments (GALLEX/GNO and
SAGE). All very different experiments with different uncertainties, which
makes it hard to explain away. Meanwhile, there are a bunch of other
experiments that should see this effect but don't (IceCube and MINOS, KARMEN,
NOMAD, CDHS, CCFR, ...). With all this tension, most of the possible
parameters for sterile neutrinos are ruled out, but there is still a little
room. Next-generation experiments will go after the parameter space that
remains, and definitively confirm/reject the sterile neutrino hypothesis at
high confidence. See e.g. the Fermilab Short-Baseline Neutrino Program, which
puts a set of three detectors in the same neutrino beam as MiniBooNE:
[https://sbn.fnal.gov/](https://sbn.fnal.gov/).

~~~
DoctorOetker
Hi, I have a couple of questions:

If I understand correctly, as far as we thought there seem to be 3 flavours of
neutrino (electron, muon, tau neutrinos), and neutrinos carry (kinetic) energy
(and possibly some rest mass).

Historically often "different" or "new" particles just turned out to be the
same particle with different energy:

Cathode rays and electrons are the same thing, but nobody would describe the
electron in hydrogen as a cathode ray orbitinng the proton.

Beta rays also turned out to be electrons, and similarily nobody describes the
electron in hydrogen to be a beta ray orbiting the proton.

X-rays and gamma-rays are both photons, yet initially we did not know they
were the same particle, just higher kinetic ennergy.

Now my question: how do we know the neutrino flavours aren't really the same
particle but in some kind of different state, causing them to be
differentially absorbed/detected?

consider red and blue light photons and pigments, the red light would only be
absorbed by the blue pigment, and the blue light woud only be absorbed by the
red pigment, but does that mean they are different particles?

How do we know a sterile neutrino isn't just one of the known neutrinos with
little kinetic energy, or perhaps too much kinetic energy to interact?

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dphidt
The other comments are spot-on. I'll just add that the neutrinos flavors are
defined by the way they interact: electron neutrinos interact to produce
electrons, never muons. So they're quite different in that sense, and in the
current Standard Model of particle physics, they're treated as independent
particles. (This is not to say that in the future, we won't require a more
comprehensive model that could relate particles in a deeper way.)

We know from experiments like LEP (electron-positron collisions) that there
are only three kinds of neutrinos that participate in weak interactions
(electron, muon, and tau). Thus the fourth neutrino type suggested by these
anomalous oscillation measurements cannot interact via the weak force, meaning
it doesn't interact at all,* hence sterile. The only way to detect them is
through their influence on the oscillations of other neutrino types.

* They'd still feel gravity, which isn't included in the Standard Model anyway.

~~~
ianai
Thank you so much for replying! I learned quite a bit.

What is the source of neutrinos in the experiments suggesting sterile
nutrinos? Is it different from the non confirmations?

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JdeBP
Other coverage:

* By NBC: [https://news.ycombinator.com/item?id=17225957](https://news.ycombinator.com/item?id=17225957)

* By Quanta Magazine: [https://news.ycombinator.com/item?id=17210982](https://news.ycombinator.com/item?id=17210982)

