Talk:Neutrino

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References[edit]

How are they actually made?[edit]

Unless I have missed something, this article does not explain how neutrinos are made. It lists some sources of neutrinos, and it explains how antineutrinos are made ("...these are emitted during beta particle emissions, when a neutron turns into a proton"), but not neutrinos. Do protons turn into neutrons? Can someone who knows more about this add a section on this? Richard75 (talk) 23:14, 29 May 2014 (UTC)

In the introduction there is "Neutrinos are created as a result of certain types of radioactive decay, or nuclear reactions such as those that take place in the Sun, in nuclear reactors, or when cosmic rays hit atoms. There are three types, or "flavors", of neutrinos: electron neutrinos, muon neutrinos and tau neutrinos. Each type is associated with an antiparticle, called an "antineutrino", which also has neutral electric charge and half-integer spin. Whether or not the neutrino and its corresponding antineutrino are identical particles has not yet been resolved, even though the antineutrino has an opposite chirality to the neutrino." Does this not satisfy your point? To answer you question "Do protons turn into neutrons" the answer is yes. It depends on the nuclei. Beta decay#Nuclear transmutation probable explains it better than I can here.Dja1979 (talk) 00:14, 30 May 2014 (UTC)
The paragraph you quoted does not say how they are made, apart from saying it's "types of radioactive decay," which is too vague. It should not be necessary to refer to another article to find out: it should be here. Richard75 (talk) 10:56, 1 June 2014 (UTC)

65 billion neutrinos[edit]

How is "6.5×1010" an improvement on "65 billion"? It's gobbledygook to many people. Richard75 (talk) 10:53, 1 June 2014 (UTC)

PS:- There is nothing in Wikipedia:Manual of Style/Dates and numbers#Numbers to say there is anything wrong with saying 85 billion. Richard75 (talk) 18:01, 1 June 2014 (UTC)
Hello Richard75. I reverted your change. The definition of billion has some ambiguity in English-speaking countries. Outside of the US, amongst some older people “billion” means “million million” rather than “thousand million”. Anyway, later in the article it says, “65 billion (6.5×1010)”, and I think that’s the best solution. Strebe (talk) 23:17, 1 June 2014 (UTC)
Thanks. I've done it that way in the first place it appears too. Richard75 (talk) 14:17, 2 June 2014 (UTC)

Do we need to change article details about electromagnetic force?[edit]

The neutrino has spin, so it does respond magnetically to electromagnetic fields. There are some places in the article and sidebars that say it does not.

Those should be changed to say it does not respond to electric fields.67.101.139.55 (talk) 19:07, 13 November 2014 (UTC)Fred Bortz

I don't see how "spin" proves a response to electromagnetic fields. Spin causes "magnetism" only of a particle has intrinsic change, which neutrinos do not (neutrons have an internal charge distribution that takes care of this). There is no charge or dipole moment in a neutrino. I have no reason to think neutrinos respond to electric fields in any way. SBHarris 21:55, 13 November 2014 (UTC)

A neutrino has a non-zero (but really small) magnetic moment because: 1. Neutrinos have non-zero masses and three types of charged leptons (electron, muon, tauon) have different masses. 2. Neutrino spin is non-zero. On 1-loop level, a photon couples with a neutrino indirectly through a W boson or a charged lepton.2401:DE00:1:6:DC7E:4730:4652:B136 (talk) 01:29, 19 November 2014 (UTC)

Neutrino Size[edit]

The 'Size' section contains two seemingly contradictory statements: "Standard-model neutrinos are fundamental point-like particles, so they have zero volume", and "Since the neutrino does not interact electromagnetically, and is defined quantum mechanically by a wavefunction instead of a single point in space, it does not have a size in the same sense as everyday objects."

I would argue for removing the first sentence and replacing it with the second. Phuhem (talk) 09:28, 9 January 2015 (UTC)

Both these statements are problematic. I've trimmed both, but they are still not ideal. —Quondum 15:08, 9 February 2015 (UTC)

Neutrino oscillation and speed[edit]

User Phr en keeps trying to replace “Before neutrinos were found to oscillate, they were generally assumed to be massless,” with “From early on, after their prediction by Fermi, neutrinos were generally assumed to be practically massless…”. I cannot find a single improvement in this attempted replacement.

  • The statement as-is is historically factual;
  • “Practically massless” means nothing; the mass they are now known to have could be called “practically massless”;
  • User Phr en states that the section is about speed, not oscillations, but perhaps is unaware that oscillation is what requires the neutrino to have mass, and having mass is what requires neutrinos to travel at subluminal speeds;
  • The replacement yields no information about why neutrinos were assumed to be massless;
  • The replacement yields no information about why the assumption changed.

Strebe (talk) 09:58, 9 February 2015 (UTC)

I agree that the the discovery of neutrino oscillations should remain as explaining the subliminal speed. —Quondum 15:10, 9 February 2015 (UTC)
The statement as-is implies the proven existence of neutrino oscillations (actually i wrote this as-is myself when starting this section of neutrino speed - at the time people really seemed to be sure of oscillations. in the meantime it's "strong evidence for ... oscillations" or even "under the hypothesis of oscillations".) It's not for sure, and that's why the "speed" section shouldn't make it sound as proven. Phr en (talk) 09:55, 13 February 2015 (UTC)
For example this https://en.wikipedia.org/wiki/K2K_experiment#Results The neutrino oscillations have been bouncing back and forth for decades. That's why I don't believe it's a good idea to put it here. And “From early on, after their prediction by Fermi, neutrinos were generally assumed to be practically massless…” is as close as you can get. Things really were like that. However I am not in the mood for edit wars. Phr en (talk) 14:05, 13 February 2015 (UTC)
I can’t tell what your agenda is, Phr en, so it’s hard to respond meaningfully, but I will note two things.
  • What caused the physics community to change its mind about neutrino mass was the discovery of oscillation. It does not matter if (by some miracle) oscillations end up disproved. That’s irrelevant to the historical account of why physicists began to believe neutrinos have mass.
  • Neutrino oscillation orthodoxy has not bounced back and forth (oscillated?) for decades. It went from “massless/without oscillation” (pre-Super-Kamiokande, 1998) to “probably massive/probably oscillates” (Super-kamiokande), to “massive/oscillates” (K2K, 2004). Each experiment since then (why have you not quoted any of those? —see Neutrino oscillation) has increased the certainty and tightened the constraints on neutrino mass. There is no significant dissent amongst physicists. Strebe (talk) 18:14, 13 February 2015 (UTC)
Point of View. The hype is with the oscillations and has been for decades. Experimenters are more careful, like the above link ("hypothesis"). And here, for example "Disappearance" http://kamland.lbl.gov/Dissertations/IwamotoToshiyuki-DoctorThesis.pdf (no oscillation in the title)- And even re-appearnce experiments have to be looked at really carefully for things that can appear in a neutrino beam. And if I want to be totally crazy I consider this as a very macabre neutrino experiment http://www.ippnw.eu/en/nuclear-energy-and-security/?expand=176&cHash=abf6cd63d1039982b6a4eb0573dc7beb&type=1 Phr en (talk) 22:55, 13 February 2015 (UTC)
The first reference you give here works within the framework of accepted neutrino oscillation, supporting it (or should I say, taking it for granted). The second doesn't appear to mention neutrinos at all. What are you trying to say? —Quondum 23:17, 13 February 2015 (UTC)
Exactly. It works within the framework of neutrinom oscillation (why "accepted"?), but neutrino oscillations can't be taken for granted. So far there is no proof for oscillations, however it "works with it". Hence n.o. could be mentioned in this section on "speed" as hypothesis, but not be taken for granted. Phr en (talk) 05:16, 14 February 2015 (UTC)
To put it more specifically: neutrino disappearance and appearance (of any given type) are phenomena that are direct evidence for neutrino oscillations (oscillation between the three types of neutrino). The measurements thereof are measuring the rate of this oscillation. You seem to be trying to suggest that there is doubt about the existence of the oscillation, yet have not produced anything that even hints at this doubt. You have produced references, and failed to show how they are relevant to the point you seem to be trying to make. You have not even used anything in any reference to substantiate your apparent point. —Quondum 15:01, 14 February 2015 (UTC)
What are you talking about? References? I said "n.o. ... not be taken for granted". If you take n.o. for granted, tell me why. And I say again that experimenters wouldn't agree with you, but be more careful about it (They are not really true believers. I gave some examples for that above.) ... And I know from experience that as late as in the early 80s, even some distinguished physicists would have gotten the fits if you asked them about measurements of the speed of neutrinos - they took it for granted that neutrinos travel at the speed of light, back then. - That, in fact, "inspired" me to start this section on neutrino speed. I repeat again that n.o. may appear in the section but as "hypothesis". Phr en (talk) 21:17, 14 February 2015 (UTC)
There’s no such thing as a proven physical theory. There are only degrees of confidence. The degree of confidence in neutrino oscillation has long passed the point where taking it for granted could be considered risky. What you say about the early 80s is true—and in fact you could say the same about mid 90s—but the world has long since moved on due to the overwhelming evidence accumulated over the past 16 years. Meanwhile the references you give are irrelevant or do not support your claims. (For the KamLAND thesis, the lack of “oscillation” in the title is irrelevant; the paper is an early work on the matter. The term appears throughout the thesis and page 117 states “the probability of no oscillation is found to 0.05%”. The “Childhood Leukemias Near Nuclear Power Stations” has nothing whatever to say about neutrino oscillation or even about neutrinos except by some wild flight of imagination. The K2K experiment#Results reference is phrased reasonably for 2004, when physicists were still cautious due to the 60 year history of assuming massless neutrinos. Meanwhile you quote nothing modern.) It’s clear this conversation won’t result in improving the article, so I will bow out until it can. Strebe (talk) 04:31, 15 February 2015 (UTC)
There is no experiment that clearly shows a neutrino oscillation, mostly they show some disappearance etc that are consistant with oscillations - that's not an "overwhelming evidence". That's why this section on speed should mention n.o. as hypothesis only.
The page 117 you mention states "For the first time, KamLAND has detected ... disappearance ..."
BTW KamLAND didn't even determine the source neutrino flux themselves but got it from TEPCO. Same true for Double Chooz in a way (from EDF and modells). ... Now, an oscillation means "back and forth" and so on , or "disappear and reappear", "disappear and reappear", and so on. But so far, the experiments show only disappearances from a predicted source strenght obtained from modells. Well if you want to call that a strong and overwhelming evidence for oscillations, go on believing that for your own pleasure.
BTW the KiKK has a better stastical evidence than other neutrino experiments. Phr en (talk) 08:47, 15 February 2015 (UTC)