Talk:Sterile neutrino

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why are we looking for them?
Which theories expanding the standard model predict a sterile neutrino? Does string theory? - Saibod 14:32, 18 April 2007 (UTC)
 * Yes, see also IceCube Neutrino Detector, under "Possible tests". -- Northgrove 16:40, 29 April 2007 (UTC)

I read about the experiment conducted by Fermilab and I wouldn't say they announced they had not found any evidence of the sterile neutrino. The article states that During their experiment an unexplained anomoly in the data left open a more exotic possibility that some scientist speculate was caused by a new kind of neutrino that can take shortcuts through the extra dimensions. Also, MiniBooNE's results closely tracked the predictions made by Heinrich Päs, Sandip Pakvasa, and Thomas J. Weiler. The prediction made by those three scientist was, if the brane that contains our universe is curved or microscopically deformed, then sterile neutrinos could take shortcuts through the bulk. These shortcuts would influence the flavor oscillations, increasing the probability of a transition at certain energies. The article is in the August issue of Scientific American, page 26 if you are interested. NucPhy7 02:46, 25 July 2007 (UTC)

Handedness vs particle/anti-particle
The lead currently says that sterile neutrinos are right-handed, while sterile anti-neutrinos are left-handed. I would argue that this need not be true and that it has been written under the assumption that they are simply the right-handed singlet neutrino fields that are "missing" from the Standard Model (and also with some additional theoretical prejudice from the seesaw model). In fact, for active Majorana neutrinos, only the handedness defines it as a "neutrino" or "anti-neutrino" (through the weak charged current interaction with the corresponding charged lepton - the lepton couples to the left-handed part - thus the "neutrino" - while the anti-lepton couples to the right-handed part - thus "anti-neutrino"). For a sterile neutrino, no such distinction is possible by definition, since they do not interact with charged leptons. In fact, had the LSND results been correct, the left-handed field would most likely be called the "neutrino" since it would be the state mixing with the active neutrinos (and the right-handed field would mix with the anti-neutrinos). Unless someone strongly opposes, I would remove the mentioned statement. --Blennow (talk) 00:17, 3 March 2009 (UTC)
 * But I believe they do interact with other particles -- albeit very very weakly. --Michael C. Price talk 23:14, 19 November 2009 (UTC)
 * The left and right handed neutrino do interact, for non-zero mass eigenmodes -- via the Higgs. Also: one additional force is permitted by the Standard Model (i.e. one which satisfies the restrictions posed by the triangle anomaly): namely, that coupled to the difference (Baryon Number - Lepton Number). For such a force, ordinary matter would provide a large positive source, while right-neutrinos would be negatively charged. Such a force would show up (if at all) by a slight difference in the weights of different isotopes and by the gravitational signature of an unseen cloud of right neutrinos around large masses, like galactic cores or black holes. Of course, if the neutrino has a Majorana mass (or a mixing of Dirac and Majorana modes) then things get more complicated. There is room for an additional Majorana term to be inserted into the Yang-Mills-Higgs Lagrangian provided by the Standard Model without inconsistency. So, it's not so much a question of *if*, but "how much, if so?"

All sterile neutrinos are right handed. But are all right handed neutrinos sterile? It seems to me that they are. Am I right?

Also, left- and right-handed neutrinos have different quantum numbers. How, therefore, can they mix? --Michael C. Price talk 14:19, 20 November 2009 (UTC)

The discussion concerning handedness needs to be revised. Here is the run-down: the charge for the weak force is proportional to left-helicity. Therefore, since the charge is an invariant, only particles of the type for which helicity is invariant (i.e. "helical luxons", or luxons or light-speed particles for which the 3-space component of the Pauli-Lubanski vector is parallel to the momentum) can interact with that force. The Higgs mechanism is to explain how these light-speed particles can have the *appearance* of slower-than-light particles -- they key point of this being that they are *not*! They only look like they are. The appearance comes by way of the interaction between the left and right helical modes ... intuitively, a kind of zig-zagging reminiscent of "zitterbegegung". Likewise, the appearance of mass arises by these means, as well. The explanation given on the page has it all backwards. The "mass" described for neutrinos (or other fundamental leptons or baryons) is actually the coupling to the Higgs for fundamental particles that are fundamentally massless. Thus, for instance, when people state (as was done formerly) that the left-neutrino is "massless" [sic], what that meant was that it did not interact with the Higgs. What the discovery of neutrino oscillation actually showed was that the left-neutrino interacts with the Higgs. And, again, following up on my brief comment above, this can take place either by an ordinary Dirac "mass" term (which would have left and right helical modes coupling through the Higgs), Majorana "mass" term (which would have left helical models self-coupling through the Higgs; ditto even for right-helical modes) or even a combination of the these. — Preceding unsigned comment added by 204.128.235.10 (talk) 20:16, 5 June 2018 (UTC)

The merge proposal
The merge proposal with Neutral heavy lepton I'll remove the proposal as being obsolete and ignored. Rursus dixit. ( m bork3 !) 18:23, 29 August 2011 (UTC)
 * 1) occurred in November 2009,
 * 2) the proposer didn't explain why, and
 * 3) the proposal haven't been discussed once.
 * He probably proposed it because the two articles are about the same thing, mostly. The only difference is that this one discusses the possibility of light sterile neutrinos while the other does not. They should be merged immediately. But, since it seems none of our physics articles have been updated since around June 2009, he probably gave up. I wonder what happened to all the physicists here. 99.146.122.70 (talk) 15:28, 15 September 2011 (UTC)
 * I merged them.

Oops! I didn't see it said "smaller eigenvalue"!

166.147.102.130 (talk) 12:05, 17 October 2011 (UTC) Collin237

Scientific American References
Scientific American (sa.com) has moved almost all of their historical content behind a paywall, and the references are now unreachable. Redwolfe (talk) 22:13, 14 February 2014 (UTC)


 * WP:PAYWALL Paradoctor (talk) 15:22, 27 February 2014 (UTC)

Mass formula
There is a problem with the mass matrix. The smaller mass eigenvalue is negative:
 * $$m_{\nu} = - \frac{m_D^2}{M_{NHL}}$$

Negative mass is physically unacceptable. Aoosten (talk) 22:53, 27 February 2014 (UTC)

Article translated into french
Thanks to all the éditor : this article has now been translated and merged into the previous french version. Thanks a lot. Regards and Hop ! Kikuyu3 (talk) 20:22, 2 September 2014 (UTC)

News
http://www.csmonitor.com/Science/2016/0809/Quest-for-sterile-neutrinos-ends.-What-does-it-mean-for-particle-physics

Haven't changed anything, a bit over my head. Farmer Brown (talk) 18:43, 9 August 2016 (UTC)

Higgs Fields and Sterile Neutrinos.
I'm seeing Higgs Fields everywhere, gravitational waves and large particles everywhere. I will continue to observe. FearlessFostic1111 (talk) 13:40, 20 December 2016 (UTC)

4.8 sigma
says miniBooNE report a 4.8 sigma result. - Rod57 (talk) 14:22, 7 June 2018 (UTC)

Planck result summarized inaccurately
Currently, the text of the article says:
 * The Planck Satellite 2013 data release is compatible with the existence of a sterile neutrino. The implied mass range is from 0 to 3 eV.[12]

But that's not what the cited paper actually says. Rather, "0 to 3 eV" were the bounds of their uniform Bayesian prior on the sterile neutrino's effective mass. In other words, this is just the starting point of their model (before considering their measured data), not the result. The results of their calculation in section 6.3.3 give a 95% confidence upper bound on the effective number of neutrino species as N_eff < 3.80, with a corresponding upper bound on the effective mass of the sterile neutrino as m_eff < 0.42 eV.

I could edit these numbers into the article, but I think it would be misleading without going into a whole tangent about what is meant by "effective" in the above. The text indicates that you could have non-relativistic sterile neutrinos with a large physical mass, while still having small m_eff and having N_eff close to 3 -- in this case the experiment can't distinguish the sterile neutrinos from cold dark matter. In fact, the upper bounds on N_eff and m_eff I referenced above are based on assuming the sterile neutrino has a physical mass no more than 10 eV (or 20 eV depending on the model they use). The motivation for this is that sterile neutrinos with mass of about 1 eV were proposed as a solution to the MiniBoone anomaly.

So I think a better summary would not imply that the cited Planck paper says anything definitive about the existence of sterile neutrinos in general, but would say that it is not compatible with the light sterile neutrinos suggested by the MiniBoone result. (The paper actually uses the term "marginally compatible", but subsequent analyses of the Planck data state this more strongly, like this one that describes the disagreement as a "strong tension". --Tim314 (talk) 03:06, 8 June 2018 (UTC)

Fundamental Force Interactions?
The opening sentence reads "Sterile neutrinos (or inert neutrinos) are a hypothetical particle[1] (neutral leptons – neutrinos) that interact only via gravity and do not interact via any of the fundamental interactions of the Standard Model."

Doesn't this contradict itself as gravitation is one of the fundamental interactions? 24.146.253.25 (talk) 02:14, 21 June 2018 (UTC)

The standard model currently does not include gravity, only the 3 other forces, so I don't believe there is a contradiction. If you believe the opening sentence is still confusing, we can rewrite it to be clearer. Kdmeaney (talk) 03:22, 27 December 2018 (UTC)