Talk:Neutrino oscillation

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[edit] math typo

I changed

\left| \nu_{a} \right\rangle = \sum_{a} U_{ai}^{*} \left| \nu_{i} \right\rangle\,

to

\left| \nu_{a} \right\rangle = \sum_{i} U_{ai}^{*} \left| \nu_{i} \right\rangle\,

because the former was obviously wrong. Someone with more knowledge should check if this is now correct. 193.171.121.30 11:27, 7 February 2006 (UTC)

Thanks. That was the right fix. linas 01:54, 8 February 2006 (UTC)

[edit] Neutrino Parameters and Their Values

Can anybody define these parameters? I guess they correspond to the angles that the mass and flavor eigenvectors form but they are never mentioned in the text. Poszwa 02:48, 20 March 2006 (UTC)

They seem to be at least somewhat explained now. What do you think? Strait 22:35, 13 July 2006 (UTC)

[edit] Mixing Matrix Definition

I think the Mixing Matrix might be defined the wrong way round. U_{lk} is the co-efficient of mass state |v_{l}> in weak state |v_{k}>, not the other way round. Not so much wrong, as just different to the general convention I suppose.

I'm not sure how clearly I've put that, but hopefully it makes sense. Can an expert check this? (See, for instance, Author: Giunti, arXiv:hep-ph/0611125v1)

128.250.54.30 07:21, 3 July 2007 (UTC) Alex

[edit] Fermions are matterparticles?

The article states that fermions are "matter particles". I think this formulation is awkward, since combining two fermions creates a boson, which could still be a matter particle. I think that comment should be removed. Andersa 12:16, 11 April 2006 (UTC)

Then be bold and remove it! —Keenan Pepper 13:55, 11 April 2006 (UTC)

[edit] Neutrino interference compared to oscillation

I went through a long discussion on PhysicsForums with a student who was convinced that neutrino oscillation was incompatible with the rules of physics, specifically conservation of energy. His problem was that the flavor eigenstate neutrinos do not have well defined mass, so he concluded that the process could not have well defined energies.

I finally got him to at least agree that neutrino oscillation was compatible with the assumptions of QM by describing the situation from the point of view of the neutrino mass eigenstates. See post 47 in http://www.physicsforums.com/showthread.php?t=115360&page=4

When looked on in this way, while flavor eigenstate neutrinos oscillate, the mass eigenstate neutrinos interfere. That is, all three mass eigenstate neutrinos contribute to the combined process of decay (in the sun) and absorption (at the detector), and since the experiment cannot distinguish which of the neutrinos was involved (as their masses are so very small compared to the energies involved), the rules of QM say that one must add together the diagrams for all three masses before computing probabilities.

The result is that the three massive neutrinos interfere with each other in the same manner as a photon interferes with itself in the 2 slit experiment. It's a great illustration of how the rules of QM are used in QFT.

I think that this should be added to the discussion for two reasons. First, it illustrates a principle of QM and Feynman diagrams. Second, it resolves the confusion in the student as to where neutrinos that oscillate go. Unfortunately, while this is all very obvious, I can't find a reference that explains neutrino oscillation in this way. Does that make it incompatible with Wikipedia standards?

I'd type up a short description but I hate wasting my time. Any comments?

Carl

This is a good idea. I will eventually get around to writing it up if no one else does first. Strait 22:36, 13 July 2006 (UTC)
Ok, I have made a graphical guide to neutrino oscillations. I have not (yet?) attempted to tackle the subtle quantum mechanical points, though. Strait 02:59, 8 August 2006 (UTC)

[edit] Expert

I think that I have added enough to this page to warrant removing the expert tag. If you disagree, please put it back and say why you did so here. --Strait 18:26, 7 August 2006 (UTC)

[edit] Flavor and mass do not commute

How can we describe the mass of any neutrino flavor since they are not mass eigenstates? I ask because there is a flavor - mass table at neutrino, which would seem a contradiction in terms. --Michael C. Price talk 07:57, 23 August 2006 (UTC)

The mass of a flavor eigenstate such as the electron neutrino can be defined as a weighted average of the masses of the mass eigenstates of which it is composed. For example, if the electron neutrino is 70% ν1, 20% ν2 and 10% ν3, then the mass of the electron neutrino is 0.7m1 + 0.2m2 + 0.1m3. I believe that this mass is the appropriate mass to consider when looking at direct measurements such as those gotten by observing the electron energy in beta decay. However, I think that for some phenomena such as neutrinoless double beta decay, the flavor eigenstate's mass must be defined somewhat differently. I will look into this and add information to the appropriate places when I get a chance. --Strait 21:00, 31 August 2006 (UTC)

[edit] Oscillations in matter

"I have added the probabilities of oscillations through solar matter. I used Runge Kutta method in maple to solve the coupled equations. I'll add the theoretical discussions soon. Please comment."

Since we know that there are three neutrinos that participate in oscillation, and we know fairly well what the relevant parameters are, I would prefer that the three neutrino model be used for specific real-life cases like propagation through the sun. The two neutrino framework is all well and good when the discussion is pure theory, but it's not actually what happens.

Once you're done writing the new section on solar oscillations, the section near the top called "Solar neutrino oscillation" should be edited to reflect the addition. --Strait 22:16, 27 November 2006 (UTC)

Oh, also, if you have a good understanding of the MSW effect, you might try to improve that page. (I only just barely understand it myself, so I don't want to try.) --Strait 22:18, 27 November 2006 (UTC)

[edit] Importance

This article has been rated as being of "low" importance. I think that a phenomenon which stems directly from the (apparently) fundamental parameters which define the universe, and is the only known way of measuring those parameters, should be rated at least "mid" if not "high". I think that this page is not well described by "Subject is mainly of specialist interest." --Strait 21:34, 11 December 2006 (UTC)

[edit] Article length

Adding all the graphs has started to make the article a bit long, in my opinion. Pictures help readers understand the content, so we should leave them. I would rather see something more technical move away. General readers might look at this article after the recent publicity including a NOVA episode devoted to the subject. We could consider reseparating the Maki-Nakagawa-Sakata matrix because it contains all the numerical details unappealing to general readers. This could also discuss experiments that attempt to measure the values. Notice how the Cabibbo-Kobayashi-Maskawa matrix has its own article. Teply 03:33, 19 December 2006 (UTC)

Agree, if it can be done elegantly. If you start the process, I will be around to help. --Strait 04:31, 19 December 2006 (UTC)

Indeed I did come to this page after viewing the Nova episode, "The Ghost Particle." The question in my mind--not resolved because I don't completely follow the math in the main article about mass and flavors not being congruent: since the masses of the three flavors of neutrino differ by more than six orders of magnitude (2.2 eV, ~170 KeV, ~15.5 MeV), oscillations among flavors, in order to conserve energy, must be accompanied by changes in velocity. Is this correct? At what fraction of the speed of light do solar neutrinos travel as electron neutrinos, and how much does this velocity decrease when they assume the other flavors? 21:08 PDT, 10 April 2008 —Preceding unsigned comment added by 67.161.40.124 (talk) 04:10, 11 April 2008 (UTC)

[edit] References

Reference 4 is a vaguely related nuclear/detector physics paper that really shouldn't be quoted here. Suggest replacing with the PDG reference: "Yao et al. J Phys G 33, (2006) p156", and the references therein. —Preceding unsigned comment added by 128.250.54.30 (talk) 07:31, 22 October 2007 (UTC)

[edit] Is the neutrino flavor a "hidden variable"?

This isn't my field, and likely I'm misunderstanding - but what confuses me is that the neutrino seems only to be observed as one of three quantized flavors; yet it seems to know, internally, precisely at what point in its oscillation it is at at any given time. Given the source of the neutrino and approximate momentum it seems like you could come up with a better model of the neutrino's internal state (how likely it was to be a certain flavor and when it would turn into another) than you could actually measure. Does that make its oscillation state a "hidden variable" in the deprecated quantum mechanical sense? 70.15.116.59 (talk) 23:17, 9 December 2007 (UTC)