Talk:Neutrino/Archive 1

Archive 1

Archive 2

Archive 3

Dry cleaning fluid

The text described a detector containg "dry cleaning fluid" (DCF) which is invisibly linked to "carbon tetrachloride". Is that the right compound? (I thought that DCF was ethylene N-chloride for some N.)
Jorge Stolfi 17:45, 20 Apr 2004 (UTC)

Years ago, when I wrote a paper on this, I claimed it was C₂Cl₄. However, I would need to track down the reference that told me that. Moreover, it's possible that several different compounds have been used over the years.

Old comments

This probably needs a refactoring. Also new chapters as "history", and also a theoretical description of the neutrino interactions in the Standard Model for the more advanced users that consult the wikipedia.

Many edits described here

I'm making several individual edits, and I'll describe them here as I make them. Here goes...

• Artificial neutrino beams are all in the energy range where the cross section increases linearly with energy. (The parabolic dependence holds near reactor/solar energies.) Further, the rate increase usually takes second billing to physics and detector issues when choosing an experiment's energy. (Consider the off-axis neutrino beams: the monoenergetic flux is chosen despite the much lower event rate.) However, the energy dependence of the cross section is worth mentioning. As I continue my edits, I'll try to find a place for it. Also, I'm not really satisfied with my "high intensity man-made neutrino beams" phrasing.
• The number of light neutrinos as measured by LEP is sensitive to any neutrinos which are kinematically available to the Z decay. Thus, "light" here means <46 GeV, or half the Z mass. The definition of "light" given previously (<1 MeV) is relevant for the astrophysical and cosmological constraints in the PDG reference. These constraints are unrelated to the LEP measurements.
• I made uniform the choice of "flavor" versus "flavour". Either way is fine by me, as long as it's consistent.
• Question -- What is meant by: "However, conclusive proof that there are only three kinds of neutrinos remains an elusive goal of particle physics."? I don't think anyone seriously thinks that three is the final number and that all it just needs is just some "conclusive proof". Sterile neutrinos, high-mass partners (such as those needed in the see-saw mechanism), etc., are all up for grabs. I'll delete this line soon if no one objects.
• "tauon" --> "tau" for consistency and modernity.
• removed some text that was redundant with the flavor oscillation section.
• "beamed" --> "magnetically focussed". Sounds less magical.

Arbe 00:29, 1 October 2005 (UTC)

Large changes to the detector section

• Retitled it "neutrino detection"
• Retooled the handling of what's sensitive to which neutrinos. The previous wording implied that the detectors themselves were intrinsically sensitive to this or that neutrino flavor. Flavor sensitivity is a kinematic threshold issue rather than a detector design issue.
• Generalized the Cherenkov detector stuff.
• Various rewordings.
• Added text on veto regions.

Arbe 22:05, 1 October 2005 (UTC)

Mistake in Neutrino Oscillation Discussion

I'm not quite confident enough to change this. However, as I understand the phenomena, and in contrary to the article, Neutrinos do start out in a well defined flavor eigenstate, however, the flavor is not an eigenstate of the prophgation Hamiltonian and thus as the particle moves through space, it picks up a probability of oscillations. I'm almost sure that the article's description that "[Neutrinos] acquire a particular flavor only after an interaction with another particle has taken place. Before this interaction occurs, the neutrino is considered to be in a superposition of the 3 individual (e, mu and tau) flavor eigenstates." is incorrect because it began in a flavor eigenstate and only later became a superposition of the three flavor eigenstates. If somebody else is more sure of this and can write this comprehensibly, I would appreciate it. Lyuokdea 10:21 July 25, 2005 (US Central)

I think this is correct. I will write it, eventually, if nobody else does. -- SCZenz 16:52, 25 July 2005 (UTC)

I went back through the literature and made the revision. Thanks for the confirmation. Lyuokdea 19:28 July 25, 2005 (UTC)

Redirects

Why do electron neutrino, muon neutrino and tau neutrino redirect to this article? Shouldn't they have their own articles? The problem is that we have a template (Template:Leptons) in this article which contains links to those articles (which redirect to neutrino), and links to the corresponding antiparticles, which, as you might expect, redirect to antineutrino. --Fibonacci 00:03, 15 Feb 2005 (UTC)

The reason there aren't different articles is that, as far as we can tell experimentally, all three types act the same except for being associated with a different lepton. Because of this, I am thinking of replacing the terribly redundant Template:Leptons with Template:Elementary, which I have expanded to include electrons, muons, tauons, and neutrinos anyway. -- SCZenz 18:59, 14 July 2005 (UTC)

In fact, I have done so. -- SCZenz 19:28, 14 July 2005 (UTC)

On Petameters

Firstly, althought the petameter may be "SI", nobody uses such silly units. In the context of astronomy, the use of non-SI units such as the AU, the ly, and the parsec are completely standard. Even if one did want to denote this distance in meters, one would never use the SI prefix instead of just the scientific notation. Secondly, the particular use here of light year is not a scientific measurement; it's merely a colorful rough size estimate, as when one says a rhinoceros weighs as much as a car, or that an asteroid is the size of Manhattan. In this case petameters should go, light years should stay. IMHO, that is. -- Xerxes 17:39, 2005 May 8 (UTC)

Wikipedia articles aren't written just for astronomers. The interdisciplinary nature of SI is just as important as its international nature. Gene Nygaard 19:53, 8 May 2005 (UTC)

They aren't just written for scientists either. Many more people know what a light-year is than a petameter. Nickptar 02:06, 9 May 2005 (UTC)

I agree with Xerxes314. The peta- prefix simply isn't commonly used or understood -- not among astronomers, and not among physicists, either. I'm going to get rid of the petameters again.--Bcrowell 01:16, 9 May 2005 (UTC)

Thickness of lead is not measured in light years, either, by anybody. Back to petameters. If only one unit, it needs to be the SI unit. Gene Nygaard 02:17, 9 May 2005 (UTC)

Nobody ever uses such a thickness of lead anyway except in this particular example. Many more people understand LY than Pm. I don't mind the Pm being there (or the 10¹⁶ m), but the light-year measure should be first. Nickptar 13:52, 9 May 2005 (UTC)

Good idea, Nickptar, I like your solution! --Bcrowell 22:46, 9 May 2005 (UTC)

On units

Nice article! Shouldn't the mass of the neutrinos have the units 1eV/c^2 instead of 1eV? According to E=mc^2, it seems that this should be the case, when we solve for m.

Technically, yes. But since everybody knows c=1, putting in the extra text seems pointless. -- Xerxes 2005 July 8 14:47 (UTC)

Just to amplify on that, it is normal for physicists to use energy units to specify masses of particles, and in fact, it would be considered weird to use grams. Another way of thinking about it is that when we say "the mass of the electron is 511 keV," we really mean "the mc^2 of the electron is..." --Bcrowell 8 July 2005 15:52 (UTC)

"hypothetical"

I see that an anon has been repeatedly inserting language in the article that claims neutrinos are only hypothetical. Awfully silly, IMO, since they're no more or less hypothetical than electrons, at this point. If the anon wants to try to make a reasoned case here on the talk page, that's great. Otherwise I'll be happy to help out with reverting the changes, so everyone can avoid breaking the 3RR.--Bcrowell 23:31, 16 July 2005 (UTC)

Looks like we're in for a bit of work, then. On the off chance the anti-neutrino (heh) party would like to discuss this, it seems we have the expertise here to explain the theoretical and experimental reasons we know neutrinos exist in some detail. -- SCZenz 00:38, 17 July 2005 (UTC)

Hey, lookee there, I got a communication from SCZenz via signals supposedly transmitted using hypothetical particles called electrons! --Bcrowell 02:22, 17 July 2005 (UTC)

Huh?

How can there be 2.984±0.008 types of neutrinos? That range doesn't include 3. Yes, I followed the link and the figure is in the linked paper, but it still seems strange. Ken Arromdee 02:20, 22 August 2005 (UTC)

The number of neutrinos is a free parameter in the shape they're fitting on the Z boson mass plot. Since the plus-minus range is one standard deviation, about a third of the time the measured number will fall further from the true value than that number (simply due to statistical fluctuations). The result means either there are almost certainly actually three neutrinos, or the assumption that a the Standard Model (with an arbitrary number of free neutrinos) describes the Z shape is wrong. If it was the number 2.5±0.008, it would be pretty clear it's the latter, but as it is it's pretty clear it's the former. -- SCZenz 06:54, 22 August 2005 (UTC)

Red Shift

If one accepts the Hubble interpretation of red-shift wouldn't the same thing happen to neutrinos?

There ought to be a LOT of cold neutrinos floating around!

What limits, if any, can be set on neutrino velocity?

Cave Draco 01:59, 8 December 2005 (UTC)

Neutrinos freeze out of the Big Bang much earlier than photons do, since they are more weakly interacting than photons. Thus, they begin with much higher temperature; however, they also have longer to cool. Today the background is around 1.9K. See Hyperphysics on the Cosmic Neutrino Background. -- Xerxes 15:22, 8 December 2005 (UTC)

Its very nice that there is already an entry for neutrinos. Hopefully I'll be able to give a hand too. -- JBC

---

It says: 'In collapsing supernovae, the densities at the core become high enough (10^14 gram/cm3) that the produced neutrinos can be detected.' The last part doesn't make much sense. Perhaps it should say instead 'that matter-neutrino interactions become significant'? (IIRC, the neutrino flow from the core even has a mechanical effect, helping to push the matter outwards).Jorge Stolfi 02:41, 16 Mar 2004 (UTC)

---

Perhaps neutrino detector should be a separate page. It should include a complete list of them (it is not that big!) Also, does the section cover all neutrino detectors, or just the ones designed for extraterrestrial neutrinos? Aren't there detectors for artificial neutrinos, e.g. from accelerators and/or nuclear reactors? (IIRC, there is an anecdote about such a detector being the first "neutrino communication device")Jorge Stolfi 06:51, 16 Mar 2004 (UTC)

first detector

I added some information about the first detector (1953). It was actually an anti-neutrino detector. Does that matter? JWSchmidt 05:56, 21 Mar 2004 (UTC) Sure! Jorge Stolfi 18:41, 23 Mar 2004 (UTC)

• Nu pun intended? Wodan 21:56, Aug 27, 2004 (UTC)

Number of neutrinos generated from a nuclear power plant

The article says that a nuclear power plant may generate as many as 50000 neutrinos per second. Surely, this is wrong by a longshot? When I read about the first neutrino detector, it said that they carried out the experiment close to a nuclear reactor, since they could get as many as $10^{12}$ neutrinos per second and square centimeter. --Dolda2000 03:55, 8 Dec 2004 (UTC)

Detectors

We still need a separate article about neutrino detectors and neutrino observatories. MvR 18:18, 24 December 2005 (UTC)

[neutrino observatory]s should have a list of all of the major labs.--Dr.Worm 06:09, 25 April 2006 (UTC)

Merge with sterile neutrino

This is clearly a bad idea. Sterile neutrinos are obviously beyond-the-Standard Model physics and not the same as ordinary neutrinos. It makes no more sense to include them here than to include sneutrinos in this article. What's needed here is simply the addition of more material on sterile neutrino models. -- Xerxes 01:07, 1 March 2006 (UTC)

I agree; sterile neutrino should have its own article. I think the user who added the merge tags was just noting that there was very little material in sterile neutrino. I have removed the merge tags, and marked sterile neutrino for imprrovement. I think there could be a mention of the idea in the main neutrino article as well. -- SCZenz 01:15, 1 March 2006 (UTC)

It's not obvious to me that neutrino article should be limited to talking solely about Standard Model physics: so long as it's made obvious enough that sterile neutrinos aren't in the Standard Model, I wouldn't see a problem with its inclusion here. It just seems unnecessary to have an article on a kind of neutrino which is only a few paragraphs long, considering we don't have seperate articles for electron/muon/tau neutrinos. --Mayrel 22:26, 3 March 2006 (UTC)

chirality versus helicity. 2 possible spin states

so, helicity isn't a good quantum number if neutrinos are massive. Even if they aren't (they are), helicity is still not what is meant, it's chirality that is meant, only we can afford to be sloppy in the massless case, since they coincide. This is a very common confusion, and it would be awesome if wikipedia could be the place where this confusion is laid to rest.

Also, what's this stuff about the particle of fixed helicity realizing only one of it's two possible spin states? "(i.e., only one of the two possible spin states is realized)" I think I know what is meant, but I'm not sure how to make it correct (it's certainly not correct as it stands). I guess it's meant to be a one-sentence explanation of helicity, but it's a bad one. -lethe ^{talk +} 10:15, 5 March 2006 (UTC)

More confirmation that neutrinos have mass

http://news.bbc.co.uk/2/hi/science/nature/4862112.stm Can someone incorporate this new information into the article? I'm not sure how to do it myself. - Cold Water 21:07, 31 March 2006 (UTC)

As I read it, there is no new information that can be added from that article. It does not explain what was found with the MINOS experiment, it only gives an intro to the MINOS detector and the solar neutrino problem.

To my knowledge, they just opened the data on the neer and far detectors two months ago and they have not finished with the analysis. Although I hope that MINOS helps to prove that neutrinos have mass, I don't think that any results have been published yet.--Dr.Worm 06:57, 2 May 2006 (UTC)

This is incorrect; MINOS has already published results. See, for example, First Observations of Separated Atmospheric Muon Neutrino and Muon Anti-Neutrino Events in the MINOS Detector:

An extended maximum likelihood analysis of the observed L/E distributions excludes the null hypothesis of no neutrino oscillations at the 98% confidence level.

-- Xerxes 15:26, 2 May 2006 (UTC)

Thank you!----Dr.Worm 19:02, 16 May 2006 (UTC)

"Despite their massive nature"?

This sentence doesn't make any sense: "Despite their massive nature, it is still possible that the neutrino and antineutrino are in fact the same particle, a hypothesis first proposed by the Italian physicist Ettore Majorana." Also it doesn't seem to have much to do with the section, "Flavor oscillations". (Noting the possibility that the neutrino and antineutrino are the same makes sense, although possibly in a different section; but "their massive nature" has nothing to do with it.) Is this a mistranslation from Italian or something? Chronodm 10:27, 8 August 2006 (UTC)

"Massive" there means "has mass". The neutrinos having mass is a big part of flavour oscillation - it's impossible to have flavour oscillation without neutrinos having mass. (See Neutrino oscillation) Mike Peel 10:31, 8 August 2006 (UTC)

Okay, but what does that have to do with whether the neutrino and the antineutrino are the same particle? "Despite" implies that if neutrinos were massless, the neutrino and antineutrino would be the same particle. I'm confused. --Chronodm 10:41, 9 August 2006 (UTC)

Some concerns

The remark below about accelerator beams and the cross-section increasing linearly with energy is not quite right. The cross-section over a few hundred MeV (above the "resonances") has two relevant parts, the quasi-elastic, and the deep-inelastic, which grows linearly. The two are approximately equal in the 1GeV range. The quasi-elastic cross-section for neutrinos is close to 10^{-38} cm^2 at 1 GeV, and the deep-inelastic is 0.67 x 10^{-38} cm^2/GeV (multiply by the energy to get the number.) MiniBOONE's sample is 39% QE. The peak of the accepted nu_mu spectrum in MINOS is roughly 3.5 GeV so the QE contribution is still significant. The reason this is more than a pedantic aside is that detecting quasi-elastic charged current events is experimentally clean -- one sees nothing followed by an outgoing muon. It is also important because the quasi-elastic cross-section is not well measured and provides an important source of systematic errors in predicting the flux of neutrinos. You care about that because one wants to make a prediction of the unoscillated beam and get that right before claiming you've measured anything about the oscillation parameters. One gets around this with two-detector experiments, along the beam at two different distances, and measuring a change. The systematics of the absolute prediction then largely cancel, but still we like to get it right just for that warm and fuzzy feeling.

Old accelerator beams (like the one I designed and built) had energies anywhere from 20-400 GeV where indeed quasi-elastic contributions were small, and in fact were a background to delicate measurements of the properties of the cross-section. However, we have pretty much tapped out the physics to do with those, and none are extant.

And as long as one wants to be fussy the invisible width of the Z, which "counts" the number of light neutrino species, is a little off, and tends to point at the neutral current G_F being a little different from the charged-current G_F. But the electroweak fitting community has more things to worry about, like how come there's no Higgs yet... —The preceding unsigned comment was added by 75.21.220.219 (talk • contribs) 20:27, 5 August 2006.

Flavor and mass do not commute

How can we describe the mass of any neutrino flavor since they are not mass eigenstates? --Michael C. Price ^talk 23:39, 21 August 2006 (UTC)

For the moment I have described, in the neutrino table, the flavor mass as an "average mass". If anyone has any better suggestions (e.g. "weighted average of the mass eigenstates") please discuss/update accordingly. --Michael C. Price ^talk 18:13, 19 September 2006 (UTC)

I think that it's fine to refer to "the mass of the electron neutrino" even though it is not a mass eigenstate. It has a well defined mass in the sense that this mass provides a cutoff to the energy of the electron produced in beta decay. I think that a footnote with a bit of discussion of this distinction is the best solution. We can't explain much in the table itself without making the table really ugly. What do you think? --Strait 18:29, 19 September 2006 (UTC)

The problem with the statement "It has a well defined mass in the sense that this mass provides a cutoff to the energy of the electron produced in beta decay." is that energy cutoff would be the same with muon decay or (presumably) tau decay, as with electron (beta) decay. Using "flavor mass" = "energy cutoff" in this sense is meaningless since it is the same for all flavors. However I agree with your footnote solution -- so please go ahead with it. --Michael C. Price ^talk 21:40, 19 September 2006 (UTC)

I don't agree that the cutoff would be the same for all flavors. Or rather, let me clarify what I mean by "cutoff", since that's a sloppy way to talk about it. For beta decay, I mean that the difference in the maximum electron energy in reality and the maximum electron energy assuming zero neutrino mass. This difference should not be the same for beta decay (³H → ³He e ν_e) and π → μ ν_μ, and it should be again different for D → τ ν_τ. --Strait 22:17, 19 September 2006 (UTC)

Non-sloppy use of language also requires that we don't talk about flavor masses, any more than we would talk about any two non-commuting observables simultaneously. Since you reverted the "average mass" phrase I assume you have something better to replace it with? --Michael C. Price ^talk 00:56, 20 September 2006 (UTC)

I disagree that it is sloppy to talk about the mass of a flavor eigenstate if it is clarified what is meant by the mass. I simply don't think that "average mass" is a good clarification, because someone might think either (a) that this means that if you measure the masses of various electron neutrinos, you'll find a gaussian distribution around the given value or (b) that this means that electron neutrinos from different reactions have different mass expection values, rather than (c) that this means that every electron neutrino's mass has the same expectation value and that the possible measured values are the masses of ν_1,2,3. Since I think we have both agreed to using a footnote on the word "mass", I think that's what we should do. I will do that now. --Strait 01:32, 20 September 2006 (UTC)

Looks good. Do we need to include the possibility of four mass eigenstates? The sterile neutrino page says they may Dirac mix (=mass mix?) with the other neutrinos. Is that right? --Michael C. Price ^talk 09:00, 20 September 2006 (UTC)

My personal bias is to assume that sterile neutrinos do not exist at least until MiniBooNE publishes (reporting whether they confirm LSND). This has been "any day now" for several months. --Strait 12:59, 20 September 2006 (UTC)

I have no view on the sterile neutrino's existence, but if it existed could it mass mix with the others or not?--Michael C. Price ^talk 13:31, 20 September 2006 (UTC)

They could. --Strait 13:39, 20 September 2006 (UTC)

If the mixing angles are small (which I don't know—are they?), then the electron neutrino is mostly $\nu _{1}$ and claiming the former has the mass of the latter is reasonably accurate. -- SCZenz 21:44, 19 September 2006 (UTC)

Two out of three mixing angles are rather large. See Neutrino oscillation and [1] ( figure on page 12 ). --Itinerant1 22:01, 19 September 2006 (UTC)

Yeah, this doesn't make much sense (as it is). The PDG review linked above divides the mass eigenstates into "the solar pair" and the "isolated neutrino." It seems reasonable just to talk about the "average mass" or m₁, m₂ and m₃. –Joke 01:11, 20 September 2006 (UTC)

Detection

The article states the neutrinos can be detected via Cherenkov radiation. However, the wiki artcile states that Cherenkov radiation works with charged particles, and the neutrino carries no charge. Perhaps some addition of how neutrinos can be detected this way should be added to this article. Harley peters 01:27, 21 October 2006 (UTC)

Neutrino detectors like the one at SNO use a large amount of heavy water surrounded by photomultiplier detectors. As the neutrino's go through, a very very very small amount will interact with the electrons, protons, and neutrons via the electroweak mechanisms. the scattering causes the acceleration of these charged particles causing the Cherenkov radiation. The heavy water is used to create sensitivity to one flavor of the neutrino, the electron neutrino. Also the addition of chlorine will also provide another source of for detection of neutrinos. Althouh the underlying physics and calculations are a little daunting, the basic principle is pretty simple if you keep it in terms of scattering and ionization. you can look at the SNO webpage for some more info. i point to SNO because it was the first neutrino detector that was able to differentiate the electron neutrino flavor with the others. (and it was also the first research topic i had when i started grad school =) --Blckavnger 22:54, 15 November 2006 (UTC)

Redlinks

I'm gonna do a minor de-linking soon to get rid of some of the redlinks. It doesn't look like anyone will be making articles on those anytime soon. Freddie 02:43, 20 February 2006 (UTC)

I agree that excessive red links are bad, and visually unappealing, but I think you should leave some that you feel should have an accompanying article. In other words, keep links to pages that you think are essential to Wikipedia, even if they have not been made yet. This serves a dual purpose because it cleans up the page and it indicates to users which pages are wanted, and that it will not be a waste to invest time into them. I think these things bear in mind the overall coverage and quality. Syphondu 01:29, 31 January 2007 (UTC)

Contradiction in flavor paragraph?

Isn't there a contradiction in this paragraph:

The possibility of sterile neutrinos — neutrinos which do not participate in the weak interaction but which could be created through flavor oscillation (see below) — is unaffected by these Z-boson-based measurements, and the existence of such particles is in fact supported by experimental data from LSND. The correspondence between the six quarks in the Standard Model and the six leptons, among them the three neutrinos, provides additional evidence that there should be exactly three types.

The first sentence says there's evidence for a forth type of neutrino, the second sentence talks about "additional evidence" that there are only three. AxelBoldt 00:02, 29 December 2006 (UTC)

I agree that is a bit confusing. I had to read it twice before I got it. What is meant, I think, is the three leptons and their three antileptons correspond to the three neutrinos and their three antineutrinos. Does someone want to add this clarification? --Ctta0s 18:27, 9 March 2007 (UTC)

Typo?

"The energy of supernova neutrinos ranges from few to several 10 of MeV." What is that "10 of" doing in there? Typo? In fact, that whole sentence doesn't read right to me. Could anyone with the physical know-how be bothered to correct it? Thanks. --Ctta0s 18:34, 9 March 2007 (UTC)

Image of photo produced by neutrinos instead of photons

It'd be nice if we could have a photo produced by neutrinos and a neutrino detector instead of a typical photo using photons.

I saw a quite impressive shot here, of our Sun, with the neutrinos already having passed through Earth before reaching the detector (Super-Kamiokande)! It took the detector over 500 days to collect enough neutrinos to produce that image. I think with a description like that, some readers would more quickly gain an understanding of the unusual nature of neutrinos. I'm unsure of licensing to post that specific photo here though. -- Northgrove 12:23, 12 May 2007 (UTC)

Uses of Detection?

Are there enough artificially produced Neutrinos coming from Earth that a distant observer could notice a significant increase from naturally occurring ones to indicate our presence? If not, how much would it take? Example, if we consistently produced as much, example: our sun, making our system appear to have two 'sun sized' sources orbiting each other, but no equivalent gravitational wobble, could this second source still be dismissed as natural? And our our earth-based neutrino detector capable of such detection if the situation is reversed?

— Preceding unsigned comment added by Zerothis (talk • contribs) 14:46, 27 May 2007 (UTC)

Negative mass?

The following sentence, which I changed, implied that neutrinos are exotic matter:

Combined, these constraints imply that the heaviest neutrino must have an absolute mass at least 0.05 electronvolt, but no more than 0.3 electronvolt.

Note that the word "mass" is linked to negative matter.

This was changed in [[2]], with the comment "Mass - measuring squares does not preclude exotic matter." I can't find any preceding or following discussion on the talk page.

I'm going to assume that this is just User:Abb3w's personal crackpot theory, and revert his change, as follows:

Combined, these constraints imply that the heaviest neutrino must have a mass of at least 0.05 electronvolt, but no more than 0.3 electronvolt.

If I'm wrong, the fact that neutrinos (likely, or even plausibly) have negative mass needs to be explicitly mentioned in the article--why scientists believe this, what implications it has, etc. The exotic matter page also needs to be rewritten extensively if there are really negative-mass particles all of the place. --76.200.100.179 13:50, 2 June 2007 (UTC)

Neutrinos don't have negative mass. The limit in the text is from cosmological observations which depend on cosmological models and a variety of quantities (such as the Hubble constant) not directly related to neutrino mass. The limits in the table are from direct flavor-specific kinematic tests (e.g., pion decay for the muon neutrino.) This is implied in the table's footnote, but perhaps it could be made more explicit. Arbe 04:04, 7 June 2007 (UTC)

Well, I was pretty sure of that (which is why I edited the article), but I wanted someone to confirm that I'm not crazy, or way out of the loop.... Thanks. --76.216.99.108 12:39, 15 June 2007 (UTC)

MiniBooNE Result

The article at the time I wrote this comment says

Recent results from Fermi Lab's MiniBooNE experiment have brought into question neutrino oscillation [1]and thus the assertion neutrinos have mass. Without mass, neutrinos, like photons, could travel at the speed of light.

This is a highly misleading interpretation of the result. MiniBooNE was built to either confirm or refute the findings of the Liquid Scintillator Neutrino Detector experiment. The MiniBooNE initial results contradict the findings of only the LSND experiment not neutrino oscillations as a whole. The results of LSND indicated a fourth $\Delta m^{2}$ oscillation parameter therefore requiring at least a fourth neutrino mass eigenstate. To explain this result without conflicting with other oscillation experiments requires a fourth neutrino flavor, a so called sterile neutrino which doesn't interact by via the weak force (hence why it isn't observed). The only thing the result put into doubt is possibly the necessity of a sterile neutrino. The LSND results were the ones that conflicted with other the neutrino oscillation experiments which all indicate only three values of the $\Delta m^{2}$ oscillation parameter. Yes, MiniBooNE didn't see any evidence of electron neutrino appearance (as a result of sterile to electron neutrino oscillation) in the parameter space it was searching, but this is expected under the three-flavor neutrino oscillation theories. So if anything the MiniBooNE result adds further support to the current neutrino oscillation model.

For some reason, my reference to a 2007 Phys. Rev. D article was replaced with a link to a 2007 Scientific American (that cannot even be read without a subscription). Furthermore, the article in the peer-reviewed link suggests something contrary to what the SciAm article is claimed to say. Since I can't read the SciAm article, I suggest that if there are more recent results that the appropriate peer-reviewed version be linked - preferably one that has an accessible article. Ben Hocking ^{(talk|contribs)} 15:12, 23 July 2007 (UTC)

The 2007 Phys. Rev. D article has a date of (Received 3 October 2006; published 29 January 2007). The Sci Am article has a date of August 2007 (although probably written June 2007?). I agree the latter is unpeer reviewed but it definitely is an update on the earlier null results, and SciAm is generally regarded as a reliable source. I agree it is frustrating not to have on-line access to the full article (I have a paper subscription to SciAm and the August07 issue arrived today). I will hunt around for more accessible links. Please be patient. --Michael C. Price ^talk 15:35, 23 July 2007 (UTC)

OK, thanks for looking into it. Ben Hocking ^{(talk|contribs)} 15:39, 23 July 2007 (UTC)

See the update at the MiniBooNE - includes kosher reference.--Michael C. Price ^talk 15:57, 23 July 2007 (UTC)

Why does it say "nearly"?

Experimental results show that (nearly) all produced and observed neutrinos have left-handed helicities (spins antiparallel to momenta), and all antineutrinos have right-handed helicities

Does this imply that a few results did produce with the wrong handedness?

— Preceding unsigned comment added by Długosz (talk • contribs) 18:49, 20 June 2007 (UTC)

Traveling at the speed of light?

It is pretty obvious that neutrino is believed to have non-zero mass (invariant). neutrino is then could not travel at the speed of light according the Special Relativity, isn't it?

Yes, if the neutrino has a non-zero rest mass it cannot travel at the speed of light. The fact that it has been observed to travel at very close to the speed of light (indistinguishable from the speed of light) led most to assume that it did have no rest mass. All theories involving oscillations (that I'm aware of), however, require a non-zero mass - which in turn requires the neutrino to be traveling at speeds strictly less than the speed of light. Ben Hocking ^{(talk|contribs)} 17:07, 24 July 2007 (UTC)

Please watch the mass section

An editor has pasted some crackpot text into the "mass" section and carefully edited and wikified it. The text is scientific-sounding but pure gibberish.

I presume he will try to put it back in the future.

To that editor: please provide references. 201.55.113.211 02:06, 18 October 2007 (UTC)

The references are the references of the global scientific data base existing and yet to be discovered. I had added the Torino-Dubna refererence as a comprehensive summary of the status quo, dated 2003. The formulation I added , I had derived in 1995, three years before the formula was verified or supported by the Super-K publication on June 4th 1998. (It was my birthday present, showing me that my model was at least valid in terms of neutrino masses). I have followed the developments in the standard models of theoretical physics since my graduation from Queensland University, St. Lucia in 1984. There was nothing in my edit, which in any way is not supported by the scientific data base. The 'gibberish' is simply a readdressing of certain labellings in the standard models, which support it, yet extend it also.
It are censors like yourself, which hold back the advances in theoretical physics in judging content without thoughtful preponderances. I know only too well (often arguing with them on obscure forums); that an unfortunate number of 'crackpots' obscure the true and meaningful advances and ideas, which can be obtained from private sectors not affiliated with the academic establishment.
This unfortunately also has prevented my models of cosmology and a derivation of the standard model of particle physics based on superbranes to have been allowed access to a proper assessment by the experts in the fields able to advance meaningful critique and extension.

Personally, I am a 50-year old disabled pensioner from Australia now, with sole motivation of 'extending' not challenging the standard models. That is why I tried to share some pertinent information in the neutrino post. I was hoping that other researchers and experts would be able to incorporate this information in their work and advance the progress in neutrino physics because of it. If it would have found support, I could have elucidated on many other avenues of cosmology, cosmogony and the 'particle zoo' in a say 'skeletal' manner.
Lastly, I accept your censorship and shall not attempt to reedit. One can only try to share.

Tony Bermanseder, BSc. —Preceding unsigned comment added by TonyBermanseder (talk • contribs) 03:44, 18 October 2007 (UTC)

Please read the Wikipedia policy on original research. We're not trying to present the "truth" here, but what reliable, verifiable sources report. Ben Hocking ^{(talk|contribs)} 12:09, 18 October 2007 (UTC)

P.S.: If you're interested in challenging the orthodoxy, consider pursuing an MS degree. That's what I did when I pursued my "black holes don't exist" unorthodoxy (granted, it's hidden in the details). Don't tell me you're "too old" or "too poor", either. In the US, you can get your MS in physics not only for free, but with a stipend to boot. I'd be surprised if Australia didn't have similar provisions. I earned mine while working full time at a software company, and there were several students older than 50 in my classes. Ben Hocking ^{(talk|contribs)} 12:14, 18 October 2007 (UTC)

Unfortunately my revision was lost to a bot: 201.55.113.211 02:09, 18 October 2007 (UTC)

Your recent edit to Neutrino (diff) was reverted by an automated bot. The edit was identified as adding either test edits, vandalism, or link spam to the page or having an inappropriate edit summary. If you want to experiment, please use the preview button while editing or consider using the sandbox. If this revert was in error, please contact the bot operator. If you made an edit that removed a large amount of content, try doing smaller edits instead. Thanks! // VoABot II 02:04, 18 October 2007 (UTC)

Yes, I've re-deleted it. Hopefully the bot will respect me more! Ben Hocking ^{(talk|contribs)} 02:13, 18 October 2007 (UTC)

Neutrino Mass vs Gravity Question

I'm sure I missed something somewhere but, how is it that neutrinos are virtually unaffected by gravitational fields--even though they have mass?

Their mass is extremely small. -lethe ^{talk +} 07:17, 13 June 2006 (UTC)

To clarify, they are affected by gravitation as much as any other particle. However, because their mass is so small, their (relativistic) kinetic energy in most cases will be larger than their mass by a fair amount, so they will travel at nearly the speed of light. As a result, their trajectories through space will be little affected by gravitation. -- SCZenz 07:42, 13 June 2006 (UTC)

It doesn't say in the article that they're virtually unaffected by gravity. They're affected just as much as any other particle: their trajectories must be geodesics of curved spacetime. -- Xerxes 17:05, 13 June 2006 (UTC)

What evidence do we have that the Principle of Equivalence applies to neutrinos? Granting neutrino inertial mass, no problem... Gravitational mass? Show me.--Cave Draco 00:02, 23 June 2006 (UTC)

There is no evidence other than parsimony. Neutrino masses are far far too small to measure their gravitational effect, except in the great bulk of the cosmic neutrino background. Even there, you can only see hints of their presence in the rate and density of galaxy formation. Still, why would one kind of particle out of the many kinds not obey the Equivalence Principle? It doesn't make much sense. -- Xerxes 19:12, 23 June 2006 (UTC)

I wasn't actually suggesting that only neutrinos are immune to the Equivalence Principle, perhaps all leptons are immune... However, this talk section is about neutrinos and, as the only uncharged lepton, an example of neutrinos showing gravitational effects would be interesting.--Cave Draco 15:00, 24 June 2006 (UTC)

There is strong evidence that electron beams obey the ordinary law of gravitation, so it would have to be just some kinds of leptons. -- Xerxes 19:00, 24 June 2006 (UTC)

There is more than strong evidence that electrons obey the ordinary law of gravitation. If they didn't then there would be a measurable difference between inertial mass and gravitational mass; by 1 part in ~1840. 86.138.247.104 (talk) 20:25, 12 February 2008 (UTC)

SN 1987A is probably the only experimental evidence on neutrinos and gravity. The neutrinos emitted by a supernova 168,000 light years away arrived a mere 3 hours before the photons. This restricts how differently neutrinos could react to gravity. Intangir 17:28, 20 March 2007 (UTC)

---

I think it should be noted that the African American superhero Captain Marvel (of the Avengers) can transform into Neutrinos... Maybe a section on Neutrinos in pop (although comics are hardly peopular) culture is called for.

hu:User:SzDóri/Neutrínódetektorok listája

Clarification?

"Neutrinos do not exist. They are only in your mind." Does someone mind explaining this? --blarg 4/12/07 (US format)

Yes, looks like WP:Vandalism. Said: Rursus (☻) 14:47, 23 September 2008 (UTC)

Mass (text vs. chart)

According to the Mass section in the text, the sum of neutrino masses must be <0.3eV, and the heaviest neutrino must be between 0.05 and 0.3eV. The chart, meanwhile, shows upper-bound mass values for each of the three flavors as 2.2eV, 170keV, and 15.5MeV--all three of these are significantly larger than 0.3eV, and the sum is obviously outside the range as well. I think I know what this means, but it's still confusing, and needs to be explained. --76.200.100.179 13:50, 2 June 2007 (UTC)

Masses less then 2.2eV, 170keV, and 15.5MeV are from the direct mesaurements of neutrino's masses while the conclusion thet the sum of neutrino's masses must be <0.3eV is based on observation of Universe.

PS: Actually the mass of the haviest neutrino must be betwenn 45 and 110 meV - if haviest neutrino mass >100meV then other two are only few millielectronvolts lighter (the differences of the mass squares betweem the neutrinos are known to be 80meV^2, 2400meV^2, 2400meV^2) —Preceding unsigned comment added by 86.63.119.3 (talk) 01:07, 1 January 2008 (UTC)

Traveling close to the speed of light?

The opening sentence says that "Neutrinos...travel close to the speed of light." However, if a neutrino has mass and therefore doesn't travel at the speed of light, its speed depends on the observer. In particular, there is a local inertial frame in which the neutrino is at rest.

—Preceding unsigned comment added by 66.65.45.157 (talk) 00:47, 25 January 2008 (UTC)

Discovery of the neutrino

I believe that Frederick Reines and Clyde Cowan discovered the antineutrino in 1953; Sandor Szalay discovered the neutrino in 1955.[3] — RJH (talk) 17:41, 28 November 2007 (UTC)

That's a tough one, that deserves some sources lookup. It would be desirable that WP be correct in this matter. Said: Rursus (☻) 14:53, 23 September 2008 (UTC)

Solar Neutrino Power

The article states "more than 50 trillion solar electron neutrinos pass through the human body every second". What is the power equivalent of this amount of energy expressed in watts (ie, multiply the rate by the average solar neutrino energy) -- This would be a very interesting figure to quote, but I couldn't find a reference for this. If anybody has a reference, I would like to see this information added to the top of the main article. Thanks. Boardhead (talk) 18:46, 5 December 2007 (UTC)

Wait. I just realized this says "electron neutrinos". What about the other 2/3 of the solar neutrinos? Boardhead (talk) 18:57, 5 December 2007 (UTC)

Figuring the most common neutrinos are the pp variety of a maybe 200 kev, that's only a couple of watts. Three orders of magnitude below the solar constant. If you stopped them all you'd never feel it. If the Earth's atmosphere stopped them all, I'm not even sure it would cause any climate change. Of course, I could have screwed up the math a bit and it's really two orders below the solar constant, and then the extra 1% probably WOULD affect climate enough to notice. Of course, not even the entire Earth stops but a miniscule fraction of them. SBHarris 02:41, 20 January 2008 (UTC)

Shift of content

Neutrino#Neutrino detection is substantially longer than Neutrino detector.

I'd like to propose moving all but a summary of Neutrino#Neutrino detection to Neutrino detector, and additionally splitting off the detector list to List of neutrino detectors.

--Pjacobi (talk) 11:57, 15 January 2008 (UTC)

Done this. The Neutrino detector page would benefit from syncing with one of the newer review articles available. --Pjacobi (talk) 22:21, 19 January 2008 (UTC)

Neutrino lasers?

There's a known sort of "neutrino laser" from the early universe, in which (from a quick skimming it sounds like) high energy neutrinos "oscillate" into lower mass forms, releasing cold bosons in the process. It would be nice to see this detailed in the article.

The other way to interpret the "neutrino laser" phrase is as some device ("naser", as Stanislaw Lem called it in His Master's Voice (novel)) that generates a coherent beam of neutrinos by stimulated emission. This seems a bit dodgier, as there's no obvious way to reflect the beam. Still, I was lately daydreaming the great retro 1940's film New York to the Universe (2473), where Old New York was defended by mighty guns of short-lived isotopes that projected beams of neutrinos up through the ground matching the decay energies to explode any nuclear detonator that some foolish person might hope to use to damage the city's space elevators. ;) I wonder whether there is any basis in reality for nasers in any time frame. 70.15.114.2 (talk) 00:18, 13 February 2008 (UTC)

Neutrinos are fermions. There is no stimulated emission for fermions. Icek (talk) 16:46, 14 April 2008 (UTC)

Neutrinophobia

What would you call the irrational fear of being struck by a slow moving neutrino? If we're getting 4,320,000,000,000,000,000 of these pass through our bodies every day, some of them have got to be moving slowly enough to kill. --Btdonovan (talk) 17:26, 14 March 2008 (UTC)

Why would a slow-moving neutrino kill someone? Neutrino masses are extremely small (see the article) so even when one does strike an atom of my body by chance it's carrying a tiny amount of energy, certainly nowhere near enough to kill me! Olaf Davis | Talk 15:47, 31 March 2008 (UTC)

—Olaf, related to this question, if a neutrino smacked right into a proton or electron, would it be energetic enough to cause atomic ionization? Manueluribe (talk) 02:55, 21 May 2008 (UTC)

Answering the original question, I think neutrinophobia would be nice, and accepted by psychiatrists, if such a phobia would occur. Said: Rursus (☻) 14:59, 23 September 2008 (UTC)

How Energetic Are Neutrinos?

Sorry if this question is answered in the page; my knowledge of Physics terminology is limited. I am wondering how neutrinos measure up to other forms of radiation, and if this has been experimentaly measured yet or if estimates are still conjectural and theoretical. Can they be produced in mass acceleratior collisions? And if so, detected?. I'd appreciate someone in the know posting into this question. Also, if anyone knows of web pages maintained by both detection facilities I know of (the huge rock cube filled with deuterium and the polar ice detector) or any others, please post it to this question. Manueluribe (talk) 02:47, 21 May 2008 (UTC)

Non-zero Neutrino Mass and Neutrino Oscillations

The article reads as follows: "The Standard Model of particle physics assumes massless neutrinos that don't change flavor. However, nonzero neutrino mass and accompanying flavor oscillation remained a possibility." This paragraph would be more meaningful if it explained that the missing solar neutrinos were theorized to be accounted for by oscillations in flavor as neutrinos travel from the Sun to the Earth. Were neutrinos to travel at the speed of light then their individual masses would be zero. Were neutrinos to oscillate then they must be travelling at less than the speed of light, because time stands still for objects at the speed of light. Since time stands still, nothing inherent in them can change as they travel.--72.75.115.102 (talk) 23:52, 23 May 2008 (UTC)

Popular Misconceptions

well then, how much lead would a neutrino have to pass through before directly interacting with one of it's particles?

Inside the sun the electron density is very high as compared to lead. So how much less/more would the neutrino's trajectory be affected in response to the lower/higher electron densities of environments of lead vs. the interior of a star. 71.134.247.208 (talk) 02:03, 6 June 2008 (UTC)

The classical C&R reactor-neutrino experiment measured - approx -the cross section of reactor-neutrinos on hydrogen nuclei in water (just on the hydrogen nuclei - to make sure, not the oxygen nuclei in there). What's the point of comparing that to the electron density in stars? And by the way - the reactor neutrino source (spectrum) was only poorly understood. However, this cross section they derived is always around like the iron in spinach.

There are many more ways a reactor neutrino can interact with matter.Phr en (talk) 20:58, 3 July 2008 (UTC)

Energy Source?

Although neutrinos essentially do not interact with normal matter, if we could discover how to capture and convert them, we would have an inexhaustible supply of energy - we could construct neutrino collectors much as we build solar collectors today, only without many of the drawbacks. Are there any theories or research on this concept? If so, it might be an interesting subtopic to explore. —Preceding unsigned comment added by 199.117.8.254 (talk) 16:56, 1 July 2008 (UTC)

Neutrinos feel the gravity and the weak force only, and the weak force is weak and short-range. That's it. End of story. Since the weak force is all you have to catch them (the gravity intensity would require a black hole), you're stuck. If could just choose which basic laws of physics to defy, there are easier ways to get energy than that. If you could manipulate black holes or the weak force, there are easier ways to get energy. SBHarris 00:48, 2 July 2008 (UTC)

Trivia section

The Trivia section appears to have absolutely no basis in fact. Please cite references, or otherwise remove it. —Preceding unsigned comment added by Hyperdeath (talk • contribs) 19:04, 4 July 2008 (UTC)

I removed it. The section has little value, and what it tried to achieve is covered by beta decay anyway. Headbomb {ταλκ – WP Physics: PotW} 19:07, 4 July 2008 (UTC)

How do ridiculously cold neutrinos interact?

I was asking some blue-sky questions at future of an expanding universe about what happens if and when neutrinos get cold enough to coalesce under gravitation. Is there a theory of "neutrino chemistry" at ridiculously low energies?

Also, do very cold neutrinos still oscillate?

Wnt (talk) 17:27, 18 July 2008 (UTC)

Reaction cross sections

Phr en, also known as 217.229.191.206, is insisting on adding the following text under "properties":

It is often stated that "neutrinos can travel through a light year of lead unhindered". This is a popular misconception. The cross total cross section for neutrinos of any energy on lead is unknown for most reaction channels. A more correct statement would read: Neutrinos can pass through a lot of water before they can be detected by the experimental methods used in the first experiments.

It is dangerous to underestimate the interactions of (anti-)neutrinos with matter because a high (anti-)neutrino flux is generated by commercial reactors.

He is putting similar text in related articles, such as KamLAND, the effect of all of them being that we have no idea about neutrino cross sections in matter. I am a grad student studying neutrinos and I can say that there is no feeling in the community that we don't have a good idea of what these cross sections are, even if we have not measured every type of neutrino against every possible isotope. There is no doubt that we can give a good estimate for how much lead a neutrino can go through.

He does not provide any references to back up his claims. Moreover, his text is jarring and inappropriately placed. Can we come to a consensus that these paragraphs should not be here? --Strait (talk) 02:43, 15 September 2008 (UTC)

I don't know much about neutrinos, so I can't really contribute to that side of things, but it is ridiculous to replace a fairly precise quantifier such as 'a light year' with something as vague as 'a lot of'. Even gamma rays can pass through much more water than I'd care to drink.--Angelastic (talk) 12:32, 15 September 2008 (UTC)

Direct determination of the neutrino mass via kinematics

I think it might be a good idea to mention using the analysis of endpoint of the β's spectrum in the decay of tritium to find the neutrino mass. It's a fairly old idea (Fermi pointed it out in 1934) that's still being pursued.Besselfunctions (talk) 03:04, 18 September 2008 (UTC)

Neutrino size vs photon?

Are neutrinos smaller than photons? Brian Pearson (talk) 02:26, 21 September 2008 (UTC)

If these things have sizes they're too small to measure or give any indication experimentally. There's presently no indication of a "size" for any elementry particle-- either for quarks, leptons, or guage bosons. The only things that have measurable sizes are collections of particles like hadrons.SBHarris 02:30, 21 September 2008 (UTC)

Motivation?

In Motivation for scientific interest in the neutrino: is nobody interested in looking into the interior of stars, f.ex. a direct observation of what nuclei are fused, how and in what star layer? Said: Rursus (☻) 15:04, 23 September 2008 (UTC)

Add mass to infobox?

Do we want to add the estimated mass of the neutrino to the info box? (The text says est. < .3 eV) -Ravedave (talk) 05:57, 25 September 2008 (UTC)

The infobox probably needs some sort of statement about the neutrino mass. It should at least say its nonzero. The upper bound of .3 eV/c² is probably also safe to give. I would not give actually estimates as these are still subject of scientific debate, with the different estimates still spanning several orders of magnitude. (TimothyRias (talk) 08:20, 1 October 2008 (UTC))

Possibly identical to the antineutrino?

That's wrong, since otherwise reactor neutrinos would be detected in a detector for solar neutinos and vice versa. --88.68.104.4 (talk) 08:48, 30 September 2008 (UTC)

It seems like I can't find any good papers saying either way. I find "Majorana particles" mentioned, but I think that means that in some cases the neutrino and anti-neutrino can behave the same, not that they are the same particle. I dunno. IANAP, I'll see if WP:PHY can help. -Ravedave (talk) 03:30, 1 October 2008 (UTC)

I don't follow your argument, 86.68.104.4; which detectors see what has nothing to do with the difference between neutrinos and antineutrinos, but more to do with source intensity, detector placement and material, and the difference between electron, muon, and tau neutrinos. However, it is now known that neutrinos oscillate, which proves they're not purely Majorana... so "possibly identical to the antineutrino" isn't true. -- SCZenz (talk) 05:06, 1 October 2008 (UTC)

Sorry, I'm up very early in the morning, and I don't think the struck-through part of what I said is right at all. -- SCZenz (talk) 05:11, 1 October 2008 (UTC)

It is currently unknown if neutrinos are majorana particles (which would mean that they are their own antiparticle). Part of the goal for the neutrinoless double beta decay experiments (such as GERDA) is to determine whether this is the case. (certain double beta decay processes are only possible if the neutrino is a majorana particle.) (TimothyRias (talk) 08:08, 1 October 2008 (UTC))

If neutrinos are Majorana particles, then they will interact according to their chirality, i.e., a left-handed Majorana neutrino is a "neutrino" and a right-handed is an "antineutrino". The chirality flip transforming the "neutrino" into an "antineutrino" is suppressed by the small neutrino mass - just as any process which could solve the Dirac vs. Majorana issue (e.g., neutrinoless double beta decay). Therefore, "antineutrinos" would not show up in an experiment designed to measure only "neutrinos" and vice versa. --Blennow (talk) 23:49, 18 October 2008 (UTC)

Can we complete the Infobox?

I think we almost have all of the items that can be filled in except:

• Generation
• Decay particle
• Decay Time

See here for full list: Template:Infobox_Particle -Ravedave (talk) 15:29, 1 October 2008 (UTC)

Lower limit on mass?

The article only contains upper limits on mass, which normally would imply that the measured mass is consistent with zero.

However the section on Mass specifies that "Indeed, the experimentally established phenomenon of neutrino oscillation requires neutrinos to have nonzero masses." In that case, do the experiments which establish neutrino oscillation also permit the estimation of a lower limit for the electron neutrino mass, or perhaps for the sum of all three neutrino masses? If so, I think this limit would be of interest in the article. Dirac66 (talk) 03:58, 2 December 2008 (UTC)

Neutrino oscillation experiments are sensitive to the difference of the squared masses. Although those are required to be non-zero, the lightest neutrino mass is still unbounded from below. The lower bound on the second lightest neutrino depends on the neutrino mass hierarchy and is either m₂ > 0.009 eV (normal hierarchy) or m₁ > 0.05 eV (inverted hierarchy). --Blennow (talk) 22:48, 2 December 2008 (UTC)

Thanks. I put the 0.009 eV in the article to show that there is a lower bound, considering normal hierarchy for simplicity. Perhaps you could check that I have expressed it correctly. Dirac66 (talk) 03:28, 5 December 2008 (UTC)

I'll be reverting this if no source are provided.Headbomb {^ταλκ_{κοντριβς} – WP Physics} 05:16, 5 December 2008 (UTC)

Any review on neutrino oscillations should suffice for the mass squared differences, but I believe the best source would be the PDG Review of Particle physics (C. Amsler et al., Physics Letters B667, 1 (2008), see also http://pdg.lbl.gov/). Alternatively, one could use one of the papers on global fits to neutrino oscillations, but just using one of them would be entering into politics. Since masses are non-negative, going from there to a lower bound on the second lightest neutrino is simply a matter of writing two steps of arithmetics, in the normal hierarchy:

$m_{2}^{2}=m_{1}^{2}+m_{2}^{2}-m_{1}^{2}=m_{1}^{2}+\Delta m_{21}^{2}\Rightarrow m_{2}\geq {\sqrt {\Delta m_{21}^{2}}}$

The math is similar in the inverted hierarchy. By the way, the neutrino mass squared differences are referenced in the neutrino oscillation article (the reference given are the original experimental papers - although I believe that the Super Kamiokande article should be exchanged for the more recent MINOS paper, which has a more stringent bound). There is also a nice review on neutrino masses and mixings by Boris Kayser in the latest edition of the PDG Review of Particle Physics, although he is not considering the second lightest neutrino, he does remark that the heaviest neutrino cannot be lighter than ${\sqrt {\Delta m_{32}^{2}}}$, which is naturally based on the same argument. --Blennow (talk) 22:18, 5 December 2008 (UTC)

Although I see that the text may need some editing. The muon neurino does not have a definite mass, as explained in the article, and the charged lepton masses don't enter into the argument. The mass bound is on the second lightest neutrino mass eigenstate. I will see what I can do. --Blennow (talk) 22:25, 5 December 2008 (UTC)

Giving a lower limit that doesn't apply to all neutrino species runs the risk of confusion (especially since there's no lower limit for the lightest neutrino). If we're going to give a limit, I think the clearest will be the limit for the mass of the heaviest neutrino. --Amble (talk) 22:28, 5 December 2008 (UTC)

Well, no mass limit applies to any species if by "spiecies" you refer to the flavor states. This may be hard to explain in layman terms - it took me about a year to realize that what was actually going on was no different from what happens in the quark sector ... The only masses with real kinematic meaning are the masses of the mass eigenstates. If you want to put lower bounds on the effective flavor state masses, it is a question of whether you consider the effective mass in neutrinoless double beta decay or the effective mass of beta decay endpoint spectra. The three options are: 1. Clarifying that there has to be at least one neutrino mass eigenstate which has at least the mass given by the square root of the atmospheric mass squared splitting. 2. Clarifying that there hast to be at least two neutrino mass eigenstates which are at least as massive as the square root of the solar mass squared splitting. 3. Not including the lower bound at all.

Again, looking at the effective masses poses additional problems such as: Mixing implies that the effective masses can be lighter than what is quoted (consider for example the setup of the two neutrino case with maximal mixing, one zero mass neutrino mass eigenstate and one with the mass m, then both flavor states will have an effective mass of m/2). I am not really sure what is the best way to handle things. I'd be more than happy to make suggestions and check the final result though ... --Blennow (talk) 23:02, 5 December 2008 (UTC)

Thanks, but I understand the distinction. Of course, I mean that there's no lower limit to the mass of the lightest mass eigenstate. I certainly agree that it's difficult to give a lower limit in the infobox while remaining technically correct and not overwhelming or confusing the reader. I mainly meant to suggest that (1) is slightly easier to express than (2), with a note like (highest-mass state). --Amble (talk) 23:16, 5 December 2008 (UTC)

My main problem with (1) is the sad fact that the sign of the atmospheric mass squared splitting is not yet determined, which makes it difficult to be technically correct at the same time as being illuminating if one wants to give a hint on how to obtain this bound (which is what started this discussion). If you can find a good way of putting it down rigorously but still relatively non-technical, then that would be great. I cannot come up with one at the moment. --Blennow (talk) 23:36, 5 December 2008 (UTC)

What about the limit you noted above, that the heaviest state must be at least sqrt(m₃₂²)? --Amble (talk) 00:02, 6 December 2008 (UTC)

Yes, that holds. The problem is to show it in a transparent way without making reference to the mass hierarchy, since the heaviest neutrino is m₃ in the normal hierarchy and m₂ in the inverted. It is less messy to derive the lower bound on m₂ from the solar splitting since the sign is known. Anyway, I will make a try. Feel free to edit it for clarity. --Blennow (talk) 00:15, 6 December 2008 (UTC)

I seem to have had the mistaken idea that this was to go in the infobox (where the problem of clarity vs. correctness would be even worse). For the article section on neutrino mass, I like your current version but I think the previous versions are also fine. Thanks. --Amble (talk) 00:51, 6 December 2008 (UTC)

The section is much clearer now, thank you. One tiny arithmetic error: we now have sqrt(0.0027) = 0.04. Should it be sqrt(0.0027) = 0.05, or sqrt(0.0017) = 0.04? Dirac66 (talk) 01:58, 6 December 2008 (UTC)

Ah, yes. I had real problems choosing here. The point is that 0.0027 eV² is the best-fit value (although the best-fit usually changes whenever there is a new experiment), but the lower bound is 0.002 eV² (give or take, it depends on the confidence level and which global-fit paper you are looking in - but it is usually in this vicinity), which is of course also what then corresponds to the lower limit on the neutrino mass. The reasonable thing to do would probably be to quote the upper and lower bounds on the mass squared splittings, since experiments are still not accurate enough to claim that they really have the values given in the article. --Blennow (talk) 10:31, 6 December 2008 (UTC)

Reference overhaul

I updated the mass section as discussed above. However, it occurs to me that the references of this article are in need of a significant overhaul. There are now three or four citations of different versions and parts of the PDG Review of Particle physics. Different parts of the article cite different sources for parameter measurements (in some cases citing compilations of global fits, in some cases citing the original experimental reference). I am certainly not in a state (almost falling asleep is not good for getting references straight) to start digging into references at the moment. But if nobody objects, I might get around to do it when I have time. --Blennow (talk) 00:38, 6 December 2008 (UTC)

oscillations and mass

Neutrino oscillation shows that something is wrong with the standard model. However, it isn't right to take the stance that neutrinos have mass. Not until someone measures it, at least. In this case, its not so hard to describe both what physicists expect and what physicists have(or haven't) measured. The phenomena of mass is most simply an inertial effect. Physicists strongly expect neutrino mass, but have definitely never measured any inertial phenomena. Heh, have you ever tried pushing a neutrino? Anyways, it is easy and important to present the difference between theory and experiment here. Doing otherwise misinforms our readers about our state of knowledge. --Intangir 14:08, 3 January 2006 (UTC)

I'm afraid that your edits actually propagate misunderstanding of how physics is done. There are very very few measurements that are theory-independent. Overemphasizing the dependence of one particular measurement on its theoretical underpinnings makes no more sense than railing against evolution for being "just a theory". If there are other serious models of neutrino oscillation that do not imply neutrino mass, they should be mentioned in the article. Otherwise, these weasel-words serve only to distract from what is a major discovery in particle physics. -- Xerxes 17:38, 3 January 2006 (UTC)

It doesn't distract from the discovery of neutrino oscillations, it only emphasizes it. Why should we emphasize that neutrinos were 'found to have mass' when the true discovery that has been made is these oscillations. As I see it, any distraction from the real discovery here is actually caused by the lack of weasel-words.

I agree that all measurements are theory dependent to some degree. However, a direct measurement of the inertia mass of a particle is as theory-independant as it gets. Yes, 'theory-dependance' is a vague concept. So is the 'observability' of something. However, I think most would agree that inertia is definitely an observable. Heck, together with force, inertia is virtually a phenomenological definition! This is one of those cases when it is clear that there is a very high degree of theory-dependance to the claim. These physicists have discovered a phenomena consistant with the existance of positive neutrino mass. They deserve their proper kudos for this discovery. However, claiming that they have actually discovered neutrinos have mass is simply wrong. The latter statement can only mean that they have actually made some measurement of their mass, since mass(inertia) is clearly an observable! There simply isn't any such measurement to this discovery, so what exactly do you think I am 'railing against'?

I'll agree with you on a further point- Yes, this is how physics is done. Physicists regularly make hugely theory-dependant leaps. It's called induction, and its a great heuristic. None of this is motivated by a 'misunderstanding' of how physics is done. This is just run-of-the-mill scientific anti-realism. Your evolution analogy is silly and a little offensive. --Intangir 18:51, 3 January 2006 (UTC)

A simple calculation shows that the inertial mass of the neutrino has no prospect of ever being measurable using any imaginable future tech. But the more important point is that there is no observation that is ever theory-independent. If you think about it, the observation of the oscillations themselves is based on a vast theoretical framework used to generate and analyze a huge body of complicated experimental data. This is hardly different from the further analysis that leads to neutrino masses.

Specifying a bit more carefully the theoretical framework of neutrino mass calculations might be a good idea. If there were alternative frameworks (There aren't, that I know of.), it would definitely be a good idea. However, just inserting a "probably" in one particular conclusion of one particular measurement on the grounds that the measurement is somehow not direct enough, is (IMO) not good science. -- Xerxes 19:31, 3 January 2006 (UTC)

Could you show me this calculation? It seems that we have placed upper limits on neutrino masses via a couple different kinds of experiments, including those with fairly direct kinematics. If neutrino oscillations are the only observable consequence of neutrino mass, then I would have to agree that neutrino mass is rather unobservable(due to it needing to be incredibly tiny). However, this only aids my position. Why should we assert an unobservable which is only confirmed in one small way?

As for whether or not my phrasing is 'good science', the article for neutrino oscillations references this e-print. On page 4 it says, "In 1957, however, Bruno Pontecorvo realized that the existence of neutrino masses implies the possibility of neutrino oscillations." I assert that who ever wrote this is a good scientist who uses the same kind of weasely-words in precisely the same manner in regards to the same subject. While it is neat that neutrino mass is a plausible explanation, we shouldn't assert that it really is the explanation. The mainstream opinion about the nature of the evidence seems to me to be that neutrino mass is "probably" the correct explanation. Sweet. However, they certainly seem to accept the possibility that it might not be. This seems to be our state of knowledge. It would definitely be nice to describe any possible alternative frameworks, but it is absurd to suggest that not doing so is somehow some kind of "good science" excuse to misrepresent the mainstream opinion. --Intangir 20:31, 3 January 2006 (UTC)

I was talking to a retired physicist from CERN yesterday who was of the opinion that mass alone could not fully explain neutrino oscillations. He had a theory that CKM mixing could explain it. I'm afraid that I am far too dumb of a student to relay the converstaion here, but I hope you will all accept that there are opposing viewpoints out there. Although, I feel that if Intangir is insistant on presenting an alternate hypothesis, he should seek out articles to support his point.

The guy you were talking to "had a theory that CKM mixing could explain" neutrino oscillation? Neutrino oscillation isn't an observed phenomenon that requires a theoretical explanation. Rather, it's a theoretical model designed to explain certain observed phenomena (like the solar neutrino problem). But the theoretical model has been from the very start more or less identical to the CKM mixing of quarks, so this "theory" that you've heard is the standard neutrino oscillation theory, and has been since the beginning. -lethe ^{talk +} 15:31, 25 April 2006 (UTC)

Whether we've been able to quantify their mass or not is immaterial to the existence of that mass. One need not weigh a fish before one accurately reports that a fish does indeed have mass. Swamper777 (talk) 21:07, 29 May 2009 (UTC)

I have a much smaller complaint. The article implies that MINOS has detected neutrino mass, but I didn't think they even were at the data analysis point yet? If I'm wrong, please tell me! But if no one knows if they have presented any findings yet, then I feel the statement should be removed or toned down.--Dr.Worm 06:25, 25 April 2006 (UTC)

The Universe, a History Channel Show

I just learned that 60 billion neutrinos pass through our thumbnail every second. This is a quote from a professor at Berkley but I'm not sure how to properly annotate my source. It is in direct conflict with the information proposing that 50 billion of them fly through our bodies. If there is an expert who can verify this information I invite them to do so. 74.225.135.168 (talk) 05:25, 18 March 2009 (UTC)

The article states that 50 trillion of them pass through our body every second. Seems to me that both quotes might be in the right ball park. Dauto (talk) 22:36, 18 March 2009 (UTC)

Wu experiment

The article states "An experiment done by C. S. Wu at Columbia University showed that neutrinos always have left-handed chirality." Are you sure that her experiment proved the chirality of the neutrino? As far as I know it showed that the weak force is violating parity. —Preceding unsigned comment added by 137.138.170.202 (talk) 13:19, 2 April 2009 (UTC)

Etmyology

"The current name neutrino was coined by Enrico Fermi, who developed the first theory describing neutrino interactions, as a pun on neutrone, the Italian name of the neutron: neutrone seems to use the -one suffix (even though it is a complete word, not a compound), which in Italian indicates a large object, whereas -ino indicates a small one."

This is wierdly Anglo-centric. The author seems to think that Fermi took an existing English word, made a pun on the ending in Italian, and used that to generate "neutrino". The fact is that "neutrone" is not just "the Italian name of the neutron" but the original name, also coined by Fermi. The Italian scientist had two neutral particles to name and straightforwardly called them the "big neutral" one and the "small neutral" one. Appending suffixes to convey size (-one for bigness and -ino for smallness) is standard Italian word-formation. No pun involved, and no reason to say "seems". CharlesTheBold (talk) 04:23, 25 June 2009 (UTC)

The article is not quite right, but neither is your suggestion. The term "neutron" was coined by Pauli in 1930 (not by Fermi) and originally referred to what we now call the neutrino. What we now know as a neutron was discovered by Chadwick in 1932, and also called a "neutron." This left two particles with the same name, and Fermi coined the term "neutrino" as a clever way of distinguishing them. --Amble (talk) 04:46, 25 June 2009 (UTC)

Correct! SBHarris 00:06, 28 November 2009 (UTC)

Hi. I have a question. If what we now call the neutron was discovered and named in 1932, then how could one talk about the decay of a neutron into a proton/electron/antineutrino two years earlier, in 1930? —Preceding unsigned comment added by 118.6.235.15 (talk) 13:06, 29 November 2009 (UTC)

I have this question too! The article states this:

---

The neutrino[nb 1] was first postulated in 1930 by Wolfgang Pauli ... ... of a neutron into a proton, an electron and an antineutrino.[nb 2][2]

n0 → p⁺ + e⁻ + ν⁰

He theorized that an undetected particle ...

Pauli originally named his proposed light particle a neutron.

---

This paragraph suggest that Pauli was trying to explain energy difference in beta decay of Neutron into antineutrino and p⁺ + e⁻. So he named the new particle Neutron? And Fermi re-named it Neutrino?! Obviously when Pauli was explaining beta-decay, the particles involved had to have some names, but how could these names already be neutron and antineutrino! —Preceding unsigned comment added by 122.170.18.216 (talk) 09:10, 9 December 2009 (UTC)

Although neutrons hadn't been discovered yet, the atomic nucleus was known. Pauli knew that an unstable nucleus with a certain mass and charge could decay into another nucleus with different charge and a slightly different mass, emitting an electron. Later, when the neutron was discovered, beta decay could be explained in terms of the constituent parts of the nucleus. --Amble (talk) 20:05, 9 December 2009 (UTC)

Ginormous Neutrino

How does this fit into the article.

"We think of fundamental particles as being very small, but "relic" neutrinos left over from the big bang could be big. Really big. According to the 22 May Physical Review Letters, the quantum wave describing one could be billions of light-years across, a good fraction of the observable universe. Such a large wave raises questions about how a quantum particle interacts with gravity at the scale of galaxies and galaxy clusters--questions that remain unresolved."

from http://focus.aps.org/story/v23/st17 —Preceding unsigned comment added by 70.22.38.177 (talk) 18:48, 12 June 2009 (UTC)