Talk:Neutrino

History of search for mass should be seperate

When describing the mass of the neutrino, it is not necessary to tell the whole history of the search for the mass. It's best to describe some of the most recent estimates and some details, and put the history of the search in another section or another page. -- Thomas Barlow.

No lifetime given for neutrinos in the info box

The WP articles for the electron, the proton, the neutron, and many others, give a lifetime; e.g., for the electron: "stable ( > 6.6×1028 yr)." What is a suitable entry for the neutrino? Ross Fraser (talk) 06:23, 16 March 2022 (UTC)

There is none, to anybody's knowledge, so far. Cuzkatzimhut (talk) 13:08, 16 March 2022 (UTC)

It's expected to be stable (no lighter particles it could decay to), but we don't really have a method to look for decays besides ruling out lifetime values so short that they would be absurd anyway. --mfb (talk) 00:12, 17 March 2022 (UTC)

Is there succinct language that could be used in the info box to convey the above to the reader? This is useful info. Ross Fraser (talk) 00:25, 4 April 2022 (UTC)

Weird neutrino mass claims from Theo Nieuwenhuizen

The neutrino mass section contains a paragraph starting with "In 2009, lensing data of a galaxy cluster were analyzed to predict a neutrino mass of about 1.5 eV...", which contains two citations of papers by Theo Nieuwenhizen. I've quickly looked at those papers now, and they do not contain bounds on the neutrino mass under standard cosmology. Instead, these are theoretical papers about a nonstandard model where neutrinos (normal+sterile) make up all dark matter, and 1.5 eV is the typical mass of an individual neutrino species in that model. These are not upper bounds, but the rough mass needed to make his model work. The cosmological consensus is that masses this high are strongly excluded. For example, the best current bounds are that the average neutrino mass must be less than 0.03 eV (= sum of masses less than 0.09 eV), 50 times lower than Niewenhuizen's value. Since this is a theoretical prediction for an unpopular alternative model, I think just stating these numbers as they are in the page will mislead the reader. I think they should either be removed, or moved into a separate section about alternative theories on the impact of neutrinos on the growth of structure or something. Amaurea (talk) 09:01, 5 April 2022 (UTC)

Go ahead, trash the obsolete/superseded statement, and update with yours, given honest caveats. Be bold. Cuzkatzimhut (talk) 13:50, 5 April 2022 (UTC)

I removed it and cleaned up that part in general. --mfb (talk) 16:44, 5 April 2022 (UTC)

"Pauli postulated what is now called the electron neutrino" -- shouldn't that be "electron antineutrino"?

This note seems inaccurate: "More specifically, Pauli postulated what is now called the electron neutrino."

Per https://en.wikipedia.org/wiki/Beta_decay Pauli did that in 1930, presumably for beta minus decay, since beta plus decay wasn't discovered until 1934. That article also says, "In beta minus (β−) decay, a neutron is converted to a proton, and the process creates an electron and an electron antineutrino; while in beta plus (β+) decay, a proton is converted to a neutron and the process creates a positron and an electron neutrino."

Consequently, wouldn't it be more accurate to say that Pauli postulated what is now called the electron antineutrino? — Preceding unsigned comment added by 76.10.180.57 (talk) 19:49, 16 April 2022 (UTC)

Neil Turok on massless neutrinos

@Eric Kvaalen inserted a statement that the mass of the lightest neutrino "may even be zero" [1]. First on the procedure: I think that after one revert it should be up to the inserting user to justify their addition. Nevertheless, here's the justification for my revert: The quote from Neil Turok's interview that is given as a reference is rather vague and incidental. The interview appears to (it is behind a paywall and not accessible to me) and the quote taken from the interview does discuss Turok's theory on parallel universes, not neutrinos as such (if neutrino is massless, then that supports his theory). It does not say why Turok thinks that a massless remains a viable option and why we should take his statement seriously (other than because he is a respected cosmologist). This may be a very particular view point, the reader of our article cannot know. As this addition is in the lead section (which should be treated very sensitively with respect to statements that may not reflect the general state of knowledge on the subject) I think it should go. If there are more specific statements in Turok's interview that can be further supported by published literature, then the statement can stay. --Wrongfilter (talk) 17:21, 28 January 2023 (UTC)

@Wrongfilter: Thank you for your explanation. I added a couple more sentences from the interview. Yes indeed, I think that we should take his statement seriously because he is a respected cosmmologist, one of the leaders in the field. The interview is about his theory (his and Latham Boyle's) that there is a "universe" going backwards in time from the Big Bang, it's not about parallel "universes". But that's not important. At the end, he is asked "What observations would persuade people?" and he starts his answer with "Number one: show that the lightest neutrino is massless. If dark matter is composed of stable, right-handed neutrinos – as in our mirror universe picture – then this must also be true. Fortunately, within three to five years, large-scale galaxy surveys will make that measurement. If they find that it’s massless, then we’ll really be on a good road."

The article says that he will release the final paper in their series on the mirror universe later this week. I think that paper will probably also say something about this, and will provide a better reference.

I don't really understand this business of neutrino masses, but there is some explanation in the article "Sterile neutrino". It seems to me however that we don't know that the electron neutrino has mass. We know that there is a difference between its mass and that of the other neutrinos, because otherwise there would be no neutrino oscillation, but that doesn't mean that the electron neutrino mass is non-zero. (Two gamma-ray photons can collide and produce an electron-positron pair even though the photons are massless. I think that is similar.)

Eric Kvaalen (talk) 19:22, 28 January 2023 (UTC)

Nothing in the existing theory of neutrinos prohibits one of the flavors from being massless — indeed, “the” neutrino was presumed to be massless from the outset — so it shouldn’t be controversial to state that, but of course it ought to be referenced. The Turok angle given in the disputed edit is, technically, WP:SYNTH because the reasoning is “Turok et al have a theory that depends on a massless flavor of neutrino, and we trust Turok et al are not tendering baseless physical theories because their work is WP:RELIABLE”. However, in a formal paper describing their work, Turok et al state,

In particular, current experimental constraints allow for the possibility that one of the three right-handed neutrinos, $\nu _{R}$, is exactly stable. (Note that at most one of the heavy right-handed neutrinos can be stable since, for every heavy right-handed neutrino that is stable, there is a corresponding light left-handed neutrino that is massless, and we know observationally that at most one of the light neutrinos is massless.

In other words, this is known. Strebe (talk) 19:40, 28 January 2023 (UTC)

Thanks, that works as a proper reference. --Wrongfilter (talk) 20:47, 28 January 2023 (UTC)

Yeah, thanks. While I agree that "the" neutrino was originally thought to be massless, that was before neutrino oxcillation was discovered. So for a layman like me it's not entirely obvious that the electron neutrino may still be massless. By the way, I disagree with the "synthesis" policy, or at least with the way people often interpret it. It is used to prohibit any statement, not backed up by an explicit reference, no matter how obvious, that indicates the use of a little intelligence on the part of the "editor". For instance, a couple months ago I calculated the mass percentages of the components of the earth's atmosphere, from the molar percentages, and this was reverted (see Talk:Atmosphere of Earth). Eric Kvaalen (talk) 10:06, 1 February 2023 (UTC)

There is no "mass of an electron neutrino". All the flavor eigenstates (electron/muon/tau neutrino) are superpositions of the mass eigenstates. The lightest of these mass eigenstates could be massless. We don't know because mixing only gives access to differences and measurements of the absolute masses are not precise enough yet. Concerning WP:SYNTH, there is a wide range of interpretations among users. Some even "change their mind" from discussion to discussion based on what they prefer at that moment. --mfb (talk) 11:39, 1 February 2023 (UTC)

Just to clarify the history. Originally (~1930s), as stated in the article, the neutrino was postulated that the neutrino had a similar mass to the electron. It was found to be less than this, and by the time the neutrino was incorporated into the Standard Model was it thought to be massless (~1960s). Then when neutrino oscillation was discovered, at least some neutrino mass eigenstates were non-zero (~1990s). Dja1979 (talk) 18:21, 1 February 2023 (UTC)

References

Should the following apparently-redundant paragraph be removed from the article?

The resulting positron annihilation with electrons in the detector material created photons with an energy of about 0.5 MeV. Pairs of photons in coincidence could be detected by the two scintillation detectors above and below the target. The neutrons were captured by cadmium nuclei resulting in gamma rays of about 8 MeV that were detected a few microseconds after the photons from a positron annihilation event.

HOTmag (talk) 09:20, 23 October 2024 (UTC)

Why do you think that paragraph is redundant? --Wrongfilter (talk) 09:57, 23 October 2024 (UTC)

Because this paragraph is about electron-positron annihilation rather than about neutrinos, so I can't see how this paragraph has anything to do with our article dealing with neutrinos.

It seems that a user had copied this paragraph from an irrelevant source and inserted it by mistake into our article, because they probably confused "neutrons" (mentioned in this paragraph) with "neutrinos" (not mentioned). HOTmag (talk) 10:57, 23 October 2024 (UTC)

It explains how the positron and the neutron created in the reaction are detected to distinguish the signature of this particular reaction from all the background processes that are going on. It's a valid and necessary description of the Cowan–Reines neutrino experiment (see there for more details). --Wrongfilter (talk) 11:21, 23 October 2024 (UTC)

Thank you for this clarification. HOTmag (talk) 12:11, 23 October 2024 (UTC)

I agree that the entire paragraph including the quoted content is confusing. It starts with "Antineutrinos were first detected..." which is confusing since we've not yet learned about detecting neutrinos. It includes sentence ending in a colon, then "In the Cowan and Reines experiment, instead of an outgoing neutrino..." which is again is unclear where that comes from.

The section has no sources so I can't fix it. Maybe we should just delete it. Johnjbarton (talk) 16:32, 23 October 2024 (UTC)