Talk:Neutrino/Archive 6

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Spin

In the article there are these limited comments on spin: "Neutrinos have half-integer spin (½ ħ); therefore they are fermions." There is no reference to support the origin or verification of these statements. Is it possible to provide such? Has the spin 1/2 ever been challenged? Mules3 (talk) 04:08, 19 November 2019 (UTC)

@Mules3: Please start new discussions in a new section at the bottom, not somewhere in the middle in another section. You can find the spin in every textbook, it is uncontroversial and obvious from e.g. beta decay. --mfb (talk) 09:31, 19 November 2019 (UTC)

Spin–statistics_theorem. Do your due diligence. The spin 1/2 nature of the neutrino has been supported by 37,854 experiments, and counting. Cuzkatzimhut (talk) 20:18, 19 November 2019 (UTC)

Aww, come on. This is not a totally stupid question. I mean, how do we know that the electron is spin 1/2? The answer is stern-gerlach and not spin-statistics. How do we know the neutrino is spin 1/2? "Indirectly", one might say: angular momentum conservation for one, and scattering amplitudes for another. The articles on spin has no discussion of scattering amplitudes -- so where do we explain that billiard balls collide like 1/sin^4 and how that is modified for spin? It doesn't have to actually compute the misc products of gamma matrices and polarizations; it could maybe just quote the result ... Give the general flavor of angular dependence.

Heck, spin and spinor don't even talk about any of the Larmor-precession experiments that were used to demonstrate/prove that spin exists. It doesn't mention the spin-1/2 Zeeman effect used to argue that spin exists. It just promptly dives into theory -- the bog-standard textbook theory that is going to be in the midterm exams. Which, honestly, is boring AF if you're not taking mid-terms.

If you are middle-aged or retired, the history-of-physics is going to be tonnes more interesting than a waterfall of algebra... but WP articles tend to be 90% theory, whenever the theory is accessible to undergrads, and when the theory is inaccessible, the default mode is to enthusiastically quote recent news headlines. This article is mostly pretty good, but it could provide more detail on how we actually know things about the neutrino, the actual chain of logical deductions...

More generally, there is the question of "how do we know anything at all in physics?" and the easy answer is "someone ran some experiment". But when it becomes "which experiment was it, actually?", oh, well Wikipedia is mostly silent in most cases. Having wiki pages along to lines of List of experiments X that show Y to be true wouldn't be all that bad an idea. Spin is maybe less than 100 years old; the early experiments on precession in atoms are about that old, and experiments for raw naked electrons are newer than that. Whatever. A history of "how do we know the things we know." 67.198.37.16 (talk) 04:05, 9 November 2020 (UTC)

Should this get added

Possible Neutrino Decay in icecube data. Possible dark matter candidate as well.

• https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.121802
• Also quoted here. https://arstechnica.com/science/2018/09/neutrinos-may-decay-invisibly-resolving-problems-in-icecube-data

04:08, 19 November 2019‎ User:Mules3

No. There are hundreds of interesting factoids like this about neutrinos. Wikipedia does not currently have the facility, the mind-set, the editorial participation to be a clearing-house of neat-o ideas of things that might might be true. 67.198.37.16 (talk) 04:12, 9 November 2020 (UTC)

Ranges of neutrino energies from different sources

It's not easy to see how much the energy distributions from different sources overlap, eg with beta decay, and astronomical sources 1->1000 TeV (eg [1].

The greatest number of solar neutrinos are direct products of the proton-proton reaction (tall, dark blue curve on the left). They have a low energy – only reaching up to 400 keV. There are several other significant production mechanisms, with energies up to 18 MeV.

solar neutrino has the graph to the right ->
A small table somewhere in the article might be useful ?

Neutrino energies :

• stellar nuclear reactions : peak ~ 3-4 MeV, up to 10 MeV or 18 MeV,
• beta decay : "up to a few tens of MeV" Which is highest ?
• fission reactors : Is it a subset of beta decay energies ?
• supernovae & black holes : up to 1000 TeV .

--

• What's the mechanism for high energy neutrinos ? - Rod57 (talk) 18:21, 25 February 2021 (UTC)

"Electron Antineutrino" listed at Redirects for discussion

A discussion is taking place to address the redirect Electron Antineutrino. The discussion will occur at Wikipedia:Redirects for discussion/Log/2021 May 24#Electron Antineutrino until a consensus is reached, and readers of this page are welcome to contribute to the discussion. ~~~~
User:1234qwer1234qwer4 (talk) 15:04, 24 May 2021 (UTC)

"N particle" listed at Redirects for discussion

A discussion is taking place to address the redirect N particle. The discussion will occur at Wikipedia:Redirects for discussion/Log/2021 May 24#N particle until a consensus is reached, and readers of this page are welcome to contribute to the discussion. ~~~~
User:1234qwer1234qwer4 (talk) 15:13, 24 May 2021 (UTC)

lowercase sigmabot seems a bit aggressive in archiving

There's a bunch of unresolved conversations and unresolved complaints about accuracy in the archives. Archiving unresolved issues is perhaps a bit too much...!? 67.198.37.16 (talk) 04:24, 9 November 2020 (UTC)

I've set the automatic archiving time to 6 rather than 3 months as the talk page does not seem to be particularly high-traffic; I hope this helps. ~~~~
User:1234qwer1234qwer4 (talk) 15:15, 24 May 2021 (UTC)