Neutrino Oscillation: Learn About the Experiment

[michealsmith]

cann anyone tell me about tghe neutrino oscillation experimtent

 

[jtbell]

"The" neutrino oscillation experiment? There are a whole bunch of them:

http://www.google.com/search?q=neutrino+oscillation+experiment

 

[michealsmith]

ok what do u know about the T2k

 

[Gluonium]

The outcome was that Neutrino's oscilate, which means that they must have mass. This shook the standard model a bit because it predicted that they did not have mass.

If i recall correctly, they experiment was just a beam of neutrinos and on a few occaisions some of the neutrinos oscillated.

 

[arivero]

Short history: Georgi told the proton was to decay at a measurable probability, Japanese did big inversion money to build the detectors but no proton was detected to disintegrate. Then they turned the detectors into neutrino detectors and oscillation of neutrinos was detected! Big success because nobody had taken upon his shoulders the work of neutrino detection. After this, laboratory experiments are done not to confirm it but to refine the measurements so we can get some hints on the value of the mass. The recent experiment if one of these.

If the USA had filled with water the SuperCollider it had been better inversion than just to bury it.

 

[SpaceTiger]

Short history: Georgi told the proton was to decay at a measurable probability, Japanese did big inversion money to build the detectors but no proton was detected to disintegrate. Then they turned the detectors into neutrino detectors and oscillation of neutrinos was detected! Big success because nobody had taken upon his shoulders the work of neutrino detection.

On the contrary, I think Ray Davis and John Bahcall had taken quite a lot on their shoulders.

 

[jtbell]

Then they turned the detectors into neutrino detectors and oscillation of neutrinos was detected! Big success because nobody had taken upon his shoulders the work of neutrino detection.

Lots of accelerator experiments involving neutrinos had tried to detect neutrino oscillations as a sideline to their main work, but none had found any. I did a search like that as my PhD dissertation project.

The experiments that finally observed neutrino oscillations explored different energy and distance ranges, where the effects are easier to detect.

 

[ZapperZ]

Lots of accelerator experiments involving neutrinos had tried to detect neutrino oscillations as a sideline to their main work, but none had found any. I did a search like that as my PhD dissertation project.

The experiments that finally observed neutrino oscillations explored different energy and distance ranges, where the effects are easier to detect.

Er.. the MINOS collaboration had just had their first results reported here just last week! In fact, if Fermilab doesn't get funding beyond 2009 for the Tevatron, it WILL become predominantly a neutrino factory for MINOS. So I don't think it is a side project any longer.

Zz.

 

[jtbell]

Right, MINOS is very much an accelerator-based experiment. I was referring to earlier generations of accelerator-based neutrino experiments, say from the 1970s up to the early to mid 1990s. A lot of them had their data analyzed in various ways to set limits on neutrino oscillation parameters, long before the first positive evidence came from Super-K etc.

There was a colloquium at the University of South Carolina last week about the recent results, but we're at the end of the semester here so things are crazy enough with tests and exams that I couldn't take the afternoon off to drive down to Columbia.

 

[Michael Mozina]

THE CLAIM
We claim the discovery of neutrino oscillations therefore mass. In short, we observe a deficit of muon neutrinos coming from greater distances and at lower energies, from their production by cosmic rays high in the atmosphere to the detector buried deep underground. The behaviour of this deficit as a function of energy and arrival angle tells us that muon neutrinos oscillate, which is to say that they alternatingly change from one type of neutrino to another as they travel at close to the speed of light.

I have a couple of layman's questions that perhaps someone could explain.

I can't quite grasp why the absense of atmospheric muon nutrinos from the far side of the Earth automatically equates into neutrino flavor changes. In other words, why couldn't the muon neutrinos simply be more apt to be absorbed or deflected by dense mass compared to the electron neutrino?

If the fact that there are three types of neutrinos means that at least some of them must have mass, aren't we assuming different masses for different kinds of neutrinos? If they are different masses to begin with, how does a neutrino "gain or lose mass" to change to a different type? Wouldn't a change of mass violate conservation of energy laws?

Pardon my naivate' on this issue, I just don't understand how evidence of a deficit of received neutrinos of one type automatically equates into evidence of a flavor change.

 

[jtbell]

In other words, why couldn't the muon neutrinos simply be more apt to be absorbed or deflected by dense mass compared to the electron neutrino?

I haven't seen the detailed analysis of these experiments, but I'm sure it must include estimating what fraction of neutrinos of each type are absorbed while traveling through the earth, using neutrino interaction cross-sections predicted by the standard model (and studied experimentally) and current models of the Earth's structure.

how does a neutrino "gain or lose mass" to change to a different type? Wouldn't a change of mass violate conservation of energy laws?

Neutrino oscillations are not "mass oscillations." They are "flavor oscillations." The basic idea is that neutrinos of a particular flavor (e, mu or tau) do not have a single definite mass, but rather have certain probabilities of being three different masses. For each flavor, the possible masses are the same, but the probabilities are different.

According to a quantum-mechanical treatment of this system, if you create a neutrino of a particular flavor in a way that does not give you knowledge of which mass it has, its wavefunction is a superposition of the wavefunctions for all three masses. As the neutrino travels, the three wavefunctions in the superposition interfere with each other, giving oscillating probabilities for each of the three flavors. So when we detect it, it might be anyone of the three flavors. However, it has the same mass at production and at detection, chosen at random from one of the three possible values.

 

[Michael Mozina]

I haven't seen the detailed analysis of these experiments, but I'm sure it must include estimating what fraction of neutrinos of each type are absorbed while traveling through the earth, using neutrino interaction cross-sections predicted by the standard model (and studied experimentally) and current models of the Earth's structure.

The fact that neutrinos actually posess mass seems pretty "new" from a particle physics standpoint. I guess I'm a bit skeptical that we can already rule out some sort of scattering/absortion affect this early in the process.

Neutrino oscillations are not "mass oscillations." They are "flavor oscillations." The basic idea is that neutrinos of a particular flavor (e, mu or tau) do not have a single definite mass, but rather have certain probabilities of being three different masses. For each flavor, the possible masses are the same, but the probabilities are different.

I guess this concept is just hard for me to "wrap my head around". In the realm of photons, the mass of a photon does not vary, but it's wavelength changes, thus we have "high" and "low" energy photons. A photon however does not typically change energy states unless there is some kind of interaction with something else. If the 'mass' of a neutrino particle varies, how does one determine the energy state of the three types of neutrinos?

According to a quantum-mechanical treatment of this system, if you create a neutrino of a particular flavor in a way that does not give you knowledge of which mass it has, its wavefunction is a superposition of the wavefunctions for all three masses. As the neutrino travels, the three wavefunctions in the superposition interfere with each other, giving oscillating probabilities for each of the three flavors. So when we detect it, it might be anyone of the three flavors. However, it has the same mass at production and at detection, chosen at random from one of the three possible values.

I suppose that is as comprehensive an answer as I'm likely to get based on my own lack of understanding of the mechanical models that are being used to describe a triple wave function for a single particle.

I suppose I'd feel a lot better if we could aim neutrinos at a detector and measure (detect) the fact that some of the neutrinos actually changed into another form of neutrino. As it stands, it seems like a lack of a "detection" of a single kind of neutrino is simply being "interpreted" as a change from one state to another without actually seeing/detecting such the actual transition into another form. At the moment we only detect a miss, rather than detecting a hit of a different kind of neutrino. Detecting a missing neutrino is not identical to detecting a hit of a different kind of neutrino, but that seems to be the way the data is "interpreted" at the moment.

Thank you for your clear explanation of the triple wave function that is currently attributed to a neutrino. I admit I remain skeptical, but that explanation does seem to help. Thanks. :)

 

[Michael Mozina]

A couple more layman type questions came to me at lunch.

Why does current theory favor an "intrinsic triple wavelength" rather than some kind of transition occurring along the way due to say a interaction at the nuclear level? In other words, at first I originally assumed that neutrinos might change "wavelength" since a photon is a close neighbor from a mass standpoint. I could grasp how the neutrino wavelength might be affected along the way, based upon a physical process inside an atom, but I don't really "grok" the whole three wavelengths at once concept.

Wouldn't it make more sense to believe the neutrino's wavelength was altertered by an interaction with an atomic nucleus, rather than believing it has three separate wavelengths at once?

 

[jtbell]

I guess this concept is just hard for me to "wrap my head around". In the realm of photons, the mass of a photon does not vary, but it's wavelength changes, thus we have "high" and "low" energy photons. A photon however does not typically change energy states unless there is some kind of interaction with something else. If the 'mass' of a neutrino particle varies, how does one determine the energy state of the three types of neutrinos?

Remember, the mass of a particular single neutrino doesn't vary with time. Some neutrinos turn out to have one mass, some have another mass, and the rest have a third mass. The mass of any particular individual neutrino is the same at production and at detection; but the flavor at detection may be different from the flavor at production.

I suppose I'd feel a lot better if we could aim neutrinos at a detector and measure (detect) the fact that some of the neutrinos actually changed into another form of neutrino.

There are experiments in progress or in the works that are going to test this. They produce neutrinos of a specific type at an accelerator, then detect them far enough away so that oscillation effects should be significant.

In the meantime, there are results from the Sudbury Neutrino Observatory in Canada that detects electron, muon and tau neutrinos from the sun. The sum of the three flavors agrees (within experimental statistical uncertainty) with predictions of the number of electron-neutrinos produced by the sun according to standard solar models.

Earlier solar-neutrino detectors detected only electron-neutrinos, and they found fewer neutrinos than the solar models predict. This was the long-standing "solar neutrino puzzle" which has now apparently been resolved.

 

[SpaceTiger]

The mass of any particular individual neutrino is the same at production and at detection;

Aren't the neutrinos generally in flavor eigenstates at production -- that is, not in a particular mass eigenstate?

 

[jtbell]

Aren't the neutrinos generally in flavor eigenstates at production -- that is, not in a particular mass eigenstate?

Yes. And when the neutrino interacts (is detected) it does so as one of the flavor eigenstates, which may or may not be the one that it was created in. But energy and momentum are conserved, so because E^2 = (pc)^2 + (mc^2)^2, the mass of a particular individual neutrino, whichever mass it turns out to be, must be conserved. We can't know which mass it is, without making extremely precise measurements of the energies and momenta of the other particles involved in the production and decay processes, which is impossible in practice. At best we can state the probablilites that the neutrino has each of those masses.

The mass eigenstates and the flavor eigenstates are related by a matrix of coefficients, something like this:

|\nu_e> = a_{11} |\nu_1> + a_{12} |\nu_2> + a_{13} |\nu_3>

|\nu_\mu> = a_{21} |\nu_1> + a_{22} |\nu_2> + a_{23} |\nu_3>

|\nu_\tau> = a_{31} |\nu_1> + a_{32} |\nu_2> + a_{33} |\nu_3>

One of the major goals of neutrino oscillation research is to narrow down the values of the coefficients.

 

[SpaceTiger]

We can't know which mass it is, without making extremely precise measurements of the energies and momenta of the other particles involved in the production and decay processes, which is impossible in practice.

But isn't that just reducing to another Schrodinger's cat question -- i.e. whether the particle had a "real" mass and we just didn't know what it was or whether it was in a superposition of states. I'm not particularly opinionated on the issue, but it seems to be a debatable point, at the least.

 

[jtbell]

You can make some interesting parallels between neutrinos and other QM situations. For example, suppose we produce a muon-neutrino from pion decay:

\pi^+ \rightarrow \mu^+ + \nu_\mu

Suppose (hypothetically) that the pion has a very precisely known energy and momentum. They get divided up among the muon and the neutrino, so at the moment of production, the neutrino's energy, momentum and mass are uncertain. But now suppose (hypothetically again) that we measure the energy and momentum of the outgoing muon very precisely. Together with our knowledge of the pion's energy and momentum, this determines the neutrino's energy and momentum. If we do this precisely enough, we can determine which mass the neutrino has. In this case there are no flavor oscillations! When the neutrino interacts, it can still do so as any of the three flavors, but the probabilities of the different flavors are constant. They don't oscillate with time or distance traveled.

Disclaimer: I haven't actually seen this written up anywhere. It's based on my understanding of the QM of neutrino oscillations. Nobody who knows the subject well has contradicted me on this yet, but I'm definitely open to corrections.

This is very much like the classic two-slit interference setup for photons or electrons or whatever. If you make measurements that allow you to determine which slit the particle went through, you destroy the two-slit interference pattern.

 

[SpaceTiger]

But now suppose (hypothetically again) that we measure the energy and momentum of the outgoing muon very precisely. Together with our knowledge of the pion's energy and momentum, this determines the neutrino's energy and momentum. If we do this precisely enough, we can determine which mass the neutrino has.

Isn't that why the existence of neutrino oscillations suggests flavor violation in the charged sector? If the flavor eigenstates of the charged leptons weren't exactly equal to their mass eigenstates, then the energy-momentum states of the muon would be tangled with those of the neutrino. Then the experiment you're describing would be analogous to EPR -- precise measurements of the energy and momentum of the muon would cause the neutrino mass wave function to "collapse".

 

[jtbell]

Isn't that why the existence of neutrino oscillations suggests flavor violation in the charged sector?

I don't remember reading about that. Do you have a reference?

As I recall (it's been a long time since I read about this), mixing of the charged leptons isn't independent of neutrino mixing. If you start out assuming that the charged leptons also mix, you can redefine the "flavor basis states" for the charged leptons or for the neutrinos (or both? I forgot which) so as to put all the mixing with one set of particles or the other. That is, you basically combine the two mixing matrices.

Hey, I'm on sabbatical as of Monday! I've got an excuse to start doing some serious reading about all this stuff again. I might as well start with this:

http://pdg.lbl.gov/2005/reviews/numixrpp.pdf

 

[Michael Mozina]

Remember, the mass of a particular single neutrino doesn't vary with time. Some neutrinos turn out to have one mass, some have another mass, and the rest have a third mass. The mass of any particular individual neutrino is the same at production and at detection; but the flavor at detection may be different from the flavor at production.

I guess my resistance is to the notion that it changes flavors in flight as something intrinsic to the neutrino itself. I can more easily relate to a "change" that occurred in the solar atmosphere to change it from one energy state to another (like a wavelength change) but I less easily relate to assigning different neutrinos different masses and believing that the neutrino just waffles inbetween energy states for purely internal reasons.

There are experiments in progress or in the works that are going to test this. They produce neutrinos of a specific type at an accelerator, then detect them far enough away so that oscillation effects should be significant.

If we can detect a changed neutrinos from a specific and known and controlled transmitter, or I see a physical model to explain this affect, then I'll have to rethink my objections. Until that time, I suppose I'm likely to remain a bit skeptical to the idea they change flavors as an intrinsic part of being a neutrino. Even when neutrons decay into hydrogen atoms, it's a one way trip.

In the meantime, there are results from the Sudbury Neutrino Observatory in Canada that detects electron, muon and tau neutrinos from the sun. The sum of the three flavors agrees (within experimental statistical uncertainty) with predictions of the number of electron-neutrinos produced by the sun according to standard solar models.

Of course I don't personally subscribe to the "standard" solar model so that particular argument is somewhat less convincing to me than to most. :)

Earlier solar-neutrino detectors detected only electron-neutrinos, and they found fewer neutrinos than the solar models predict. This was the long-standing "solar neutrino puzzle" which has now apparently been resolved.

I suppose I'll have to "wait and see". When they detect more than a "missing" neutrino of one type, and detect a neutrino change from a known source, then I'll feel a lot more comfortable with the idea. Even then I might may not be able to rule out a single "change" of state due to an external influence.

If I'm understand you correctly, "distance" of some sort does seem to matter, but not necessarily the medium it traverses? In other words, it is not a density of material issue, it would change "flavors" even in a pure vacuum (assuming such a thing existed)?

 

[SpaceTiger]

I don't remember reading about that. Do you have a reference?

Nothing that discusses our thought experiment explicitly. There is some discussion of charged LFV here:

http://lanl.arxiv.org/abs/hep-ph?papernum=0202054"

 

[Michael Mozina]

I have another rather basic question about the current neutrino experiments.

No matter how I try to rationalize the method, I cannot logically understand how a "missing" neutrino can be considered evidence of a "changed" neutrino.

In other words, the very methods we use to detect and observe neutrinos are based upon the QM principles of scattering and absortion of neutrinos. It therefore seems very probable that a "missing" neutrino may simply have been absorbed or scattered somewhere between the transmitter and the detector. Since we can't rule out scattering/absortion proceess, I fail to understand how a "missing" neutrino can logically be equated to evidence of "flavor changing" neutrinos. Can someone explain the logic of how and why missing neturinos are interpreted to have changed flavor rather than simply being absorbed or scattered along the way? Try as I might, I just cannot understand how absorbtion and scattering were ruled out as a cause of these missing neutrinos, or why a "flavor change" is considered to be a superior explanation for these missing neutrinos.

 

[selfAdjoint]

I have another rather basic question about the current neutrino experiments.

No matter how I try to rationalize the method, I cannot logically understand how a "missing" neutrino can be considered evidence of a "changed" neutrino.

In other words, the very methods we use to detect and observe neutrinos are based upon the QM principles of scattering and absortion of neutrinos. It therefore seems very probable that a "missing" neutrino may simply have been absorbed or scattered somewhere between the transmitter and the detector. Since we can't rule out scattering/absortion proceess, I fail to understand how a "missing" neutrino can logically be equated to evidence of "flavor changing" neutrinos. Can someone explain the logic of how and why missing neturinos are interpreted to have changed flavor rather than simply being absorbed or scattered along the way? Try as I might, I just cannot understand how absorbtion and scattering were ruled out as a cause of these missing neutrinos, or why a "flavor change" is considered to be a superior explanation for these missing neutrinos.

The original Homestake detector could only respond to neutrinos of the electron type. The Solar models predicted a certain flux of electron neutrinos. Homestake only detected a third as many neutrinos as predicted. This is the "missing neurinos". The modern explanations is that the predicted flux of electron neutrinos leaves the Sun but along the way to Earth they oscillate between electron, mu, and tau types and by the time they reach the detector they are in a steady state of equal numbers in each type, so only a third of the original number in the electron type that the detector saw.

 

[SpaceTiger]

In other words, the very methods we use to detect and observe neutrinos are based upon the QM principles of scattering and absortion of neutrinos. It therefore seems very probable that a "missing" neutrino may simply have been absorbed or scattered somewhere between the transmitter and the detector. Since we can't rule out scattering/absortion proceess, I fail to understand how a "missing" neutrino can logically be equated to evidence of "flavor changing" neutrinos.

I think you're misunderstanding the measurements. It used to be about "missing" neutrinos because we only made detectors that looked for electron neutrinos. Doing so, we found fluxes that were lower than predicted by the solar model. Since then, we have observed muon and tau neutrinos that, when added with the incoming electron neutrinos, give a total flux consistent with that predicted by the standard solar model. If you wanted to explain this result in some way other than oscillations, I would think the real challenge would be finding a natural source of muon and tau neutrinos that gives a flux on the same order of magnitude as the nuclear reactions in the sun.

As for your question about neutrinos "scattering" away, we have both measurements and a well-established theory that give neutrino cross sections that are extremely low, much too low to produce significant scattering between us and the sun.

 

[CarlB]

I guess my resistance is to the notion that it changes flavors in flight as something intrinsic to the neutrino itself. I can more easily relate to a "change" that occurred in the solar atmosphere to change it from one energy state to another (like a wavelength change) but I less easily relate to assigning different neutrinos different masses and believing that the neutrino just waffles inbetween energy states for purely internal reasons.

In QM, one always has the option of analyzing the problem in whatever set of orthogonal wave functions one prefers. For the case of the neutrinos, one can analyze them in the electron, muon and tau neutrino basis, or one can analyze them in the m1, m2 and m3 basis.

Whichever way you choose, the calculation will get the same result and that will (according to current theory) match experimental results. But analyzing neutrinos in the flavor basis is a little strange. The result is just the same as what you would get if you tried to make an analysis of a particle that was partly an electron and partly a muon. The neutrinos are much more obvious and simple if you analyze them in their mass basis like you do all the other leptons and quarks.

If we analyze the problem from the point of view of the electron, muon and tau basis, then we find that the wave function starts out as a pure electron (anti) neutrino. However, to propagate a wave function through space requires that we write the wave function in the mass basis and then figure out how the three mass waves propagate, and then put it back into the flavor basis. So the result is just like what you'd get if you did the problem in the mass basis.

If you want to think of the neutrinos as physical particles (and physical particles always have masses or zero mass), then you have to work the problem in the mass basis. In that basis, the original neutrino was a mixture of three mass eigenstates when it was emitted, and then its three portions propagated differently. So, as it moves, the different masses cause the three different parts to acquire different phases and this causes them to interfere with each other.

I recently saw a great lecture on the subject, one that will take you from the beginning to a pretty complete understanding of the solar and atmospheric neutrino oscillations here:

Recent Developments in Neutrino Physics
Alexei Smirnov
http://physics.ipm.ac.ir/conferences/lhp06/notes/smirnov1.pdf
http://physics.ipm.ac.ir/conferences/lhp06/notes/smirnov2.pdf
http://physics.ipm.ac.ir/conferences/lhp06/notes/smirnov3.pdf

There is an audio that goes along with the above that can eventually be accessed by clicking on "program" here:

IPM School and Conference on Lepton and Hadron Physics
http://physics.ipm.ac.ir/conferences/lhp06/

These files are coming to you from Tehran, Iran, and you should download them and access them from your own computer instead of trying to open them directly from the webpage, at least that is what I did. The above really does explain this at a very basic and easy to understand level, but also at a very complete and good academic introduction. It goes into parametric oscillation and all that, even effects such as the different density of the core of the earth. I should mention that my work on the neutrino masses is mentioned in the above, in the cells about "empirical relations". My paper is here:
http://brannenworks.com/MASSES2.pdf

Here, let me translate the problem into the charged leptons so you can see why it is that the neutrinos are "weird".

Suppose we have a particle emitted from the sun but we don't know whether it is a muon or an electron. Instead, the particle is emitted in a combined state, call it the "chtulu" state. For example, suppose that the chtulu state is a mixture of electron and muon like this:

|chtulu> = 0.8 |electron> + 0.6 x e^{2i\pi/5} |muon>

I've normalized the above as 0.8^2 + 0.6^2 = 1. And I've put in a phase difference of 2 pi/5. But you can suppose the chtulu state is whatever mixture of electron with muon you like. (Or more generally, electron, muon and tau.)

How do we account for this in QM? What we have to do is to write the particle as a combined wave function with two sets of wave functions, one for the electron, the other for the muon. Then we let these two wave functions propagate in the usual manner, separately. At the place where the particle is received, we want to know whether it arrives as a chtulu.

To make the calculation, we recombine the electron and muon wave functions. Since the electron and muon have different masses, their wave functions will not have had the same phase change in the propagation. That could cause them to beat against each other, so even though the particles were emitted in a "chtulu", they may not be received as a chtulu. Basically, the reason is that the chtulu is not a real particle in the sense that it has a mass. The real particles are the electron and muon. For the neutrinos, the real particles are the m1, m2 and m3.

Historically, the neutrinos were once thought to be massless, so for historical reasons they are called the electron, muon and tau neutrinos. In fact, this is a deviation from the way that particles are labelled in the rest of particle physics. The real particles are the m1, m2, and m3 neutrinos. which, unfortunately, don't have consistent names.

Carl

 

[Michael Mozina]

Thank you Carl. I will have to take some time to go through the references and papers you provided, and think a bit about these concepts before I can really ask "the right" questions. I really appreciate the time you took to carefully explain the theory. I "think" I at least understand where you are coming from from a theoretical perspective. My resistance I suppose comes from conservation of energy laws in the final analysis, based on the idea that each neutrino has it's own mass/energy state. I think I'm starting to understand the intrinsic flavor changing theory a bit better and how these conservation laws are being addressed.

I suppose I am still a bit "uncomfortable" with the assumption that the flavor change is primarly a function of "time" and "distance" (assuming that I'm following your logic properly), rather than being in some way related to the medium in which the neutrino travels. Even still, I think I at least have a better understanding of the theory that flavor change is internal to the neutrino. I very much appreciate your time and effort to educate me a bit.

Would it be fair then to suggest that we should expect X amount of every type of neutrino based solely on "distance" and "time", or are you suggesting there is also an external influence involved in the transition process? In other words, if the neutrinos passed through a pure vacuum (assuming such a thing existed), would they be received as three different flavors after traveling a specific distance and length of time with no external interactions until reaching the detector?

 

[Michael Mozina]

The original Homestake detector could only respond to neutrinos of the electron type. The Solar models predicted a certain flux of electron neutrinos. Homestake only detected a third as many neutrinos as predicted. This is the "missing neurinos". The modern explanations is that the predicted flux of electron neutrinos leaves the Sun but along the way to Earth they oscillate between electron, mu, and tau types and by the time they reach the detector they are in a steady state of equal numbers in each type, so only a third of the original number in the electron type that the detector saw.

Ultimately my question and concern revolves around an internal, vs. external debate from a "causality" point of view. Let us assume for the time being that the solar neutrinos do "change" somehow between the sun and the earth. My concern is the "cause" of this change, and the "change" of energy state/mass state. Is this "change" a one time interaction, or a true "oscillation" that happens again and again? In other words, I can more easily accept that the "cause" of a one time change is somehow associated with a specific interaction with some particle between the source and the reciever. I have been less inclined to believe that neutrinos "oscillate" and change mass/energy states simply as an "internal" function.

The three wave function that Carl and others have been helping me to understand is very interesting, but I still don't see any direct evidence that would suggest that an internal "oscillation" explanation is better than an external "single change" explanation as it relates to "flavor changing".

Do you understand my concern about the difference between a one time change vs. an internal "oscillation" that happens repeatedly?

 

[selfAdjoint]

BTW, I don't know if anybody has posted on this but I just saw in the paper that Raymond Davis, who won the 2002 (I think) Nobel Prize for the original Homestake experiment that first showed the neutrino shortfall, has died. Ave atque vale frater.

 

[CarlB]

I suppose I am still a bit "uncomfortable" with the assumption that the flavor change is primarly a function of "time" and "distance" (assuming that I'm following your logic properly), rather than being in some way related to the medium in which the neutrino travels. Even still, I think I at least have a better understanding of the theory that flavor change is internal to the neutrino. I very much appreciate your time and effort to educate me a bit.

Would it be fair then to suggest that we should expect X amount of every type of neutrino based solely on "distance" and "time", or are you suggesting there is also an external influence involved in the transition process? In other words, if the neutrinos passed through a pure vacuum (assuming such a thing existed), would they be received as three different flavors after traveling a specific distance and length of time with no external interactions until reaching the detector?

Even a pure vacuum would cause neutrinos to oscillate. The presence of other matter changes things. Those links will give a damned good education in this and it will be more clear. By the way, it may have to do with interplanetary space, but technically, it's not rocket science. So keep reading and you will understand.

What's going on with conservation of energy is kind of subtle. In QM, energy is only conserved when it is present in the initial conditions. That is, it is very natural to have initial conditions for which energy is conserved, that is, the system is in an eigenstate of energy. But it is also natural for a system to be initially in a state which is not an eigenstate of energy, and for these systems, energy is not conserved.

For example, suppose the initial state is a neutron sitting out in space somewhere. Such a neutron will eventually decay (20 minute half life, if I recall) and release a neutrino. Now suppose we want this neutron to be in an eigenstate of energy. Is this possible?

No it cannot be done. Energy has to do with a system being equivalent under translations in time. This is a property that is contrary to decaying. For example, a hydrogen atom in its lowest state cannot decay and therefore can be in an energy eigenstate.

This is confusing because people often talk about the excited states of a hydrogen atom as if they were "energy eigenstates". The truth is that they are only energy eigenstates if you turn off the interaction that allows them to decay (i.e. turn off the interaction with photons).

When you analyze particles that decay along with the interaction that decays them, you will find that the energy eigenvalues are complex. The imaginary part gives the decay rate.

So you see that the problem of defining a neutron for which you know its energy precisely is a problem. Its energy is complex.

To get a neutron with a perfectly known real energy, you would have to turn the decay interaction off first and that's not a thing that is physically possible. So I'm not sure how to answer your question. In addition, when you put a particle into a perfect eigenstate of momentum, its position becomes entirely undetermined. The universe is a big place, so this is not very physical. Similarly, to get into an exact energy eigenstate, the neutron would have to live forever.

Hey, it's been 30 years since I started studying QM. It's not unlikely that I've screwed up something here. You're asking questions that are very basic, and this is stuff that one doesn't pay attention to when one gets involved in understanding the details. So please pay attention if the locals correct my interpretation.

Well at least this guy agrees with me:

"Thus the energy of a decaying state is not an eigenvalue of the system nor a constant: in particular, the energy of the state is distributed over a region with a width determined by the decay constant."
http://www.phy.uct.ac.za/courses/phy300w/np/ch1/node31.html

Carl

 

[Michael Mozina]

http://hyperphysics.phy-astr.gsu.edu/hbase/particles/neutrino.html#c1
http://hyperphysics.phy-astr.gsu.edu/hbase/particles/lepton.html#c1
http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/beta.html#c3
http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/fermi2.html#c1
http://hyperphysics.phy-astr.gsu.edu/hbase/particles/parint.html#c3

I have some more beginners questions I'm afraid. :) I did provide some of the reference materials that I have been reading tonight so that you can see where I misread something, or at least get a handle on where I'm missing or misunderstanding something I've read.

As I understand these arguements, Fermi's primary reasons for introducing the concept of a neutrino was to explain the apparent conservation of energy violation that had been observed in beta decays. By adding a third particle to "take away" some of the kinetic energy and momentum released in the Beta decay process, the energy conservation laws are again satisfied. So far, so good.

This resource also seems to suggest that reason we assume that there three different kinds of neutrinos is based on Lepton conservation laws, and the relative (three different) sizes of the various Leptons that release the different neutrinos, the Tau Lepton being 3490 times the mass of the electron.

http://hyperphysics.phy-astr.gsu.edu/hbase/particles/neutrino.html#c6

New experimental evidence from the Super-Kamiokande neutrino detector in Japan represents the strongest evidence to date that the mass of the neutrino is non-zero. Models of atmospheric cosmic ray interactions suggest twice as many muon neutrinos as electron neutrinos, but the measured ratio was only 1.3:1. The interpretation of the data suggested a mass difference between electron and muon neutrinos of 0.03 to 0.1 eV. Presuming that the muon neutrino would be much more massive than the electron neutrino, then this implies a muon neutrino mass upper bound of about 0.1 eV.

If the Leptons are different scales in size, and there is a presumed mass difference between the various neutrinos, aren't we back to violating the conservation of energy laws by claiming they change mid flight from one rest mass state to another, but also aren't we violating the conservation of Leptons rule by having them "change" as well? It seems like we went out of the frying pan, and into the fire.

http://www.sno.phy.queensu.ca/sno/results_04_02/NC/sno_nc_results.pdf

As I understand it, this paper was one of the "turning points" for the neutrino flavor changing hypothesis. While I would argue that their data does show that the "total" number of neutrinos is within expected predicted range of "total" neutrinos from the standard solar model, there does not seem to be any direct evidence of flavor changing in this data set.

The detection methods used and the equipment that is used to derive these numbers is very impressive. Having said that however, there is no direct evidence in this paper that I can see that shows where a "controlled" source of neutrinos (say tau neutrinos) was directly observed to have changed to say an electron neutrino.

The only "evidence" that I can see from that data set to suggest that the there is any actual "flavor changing" occurring between the sun and the Earth is based primarily on the assumption that the current solar theory is accurate. Am I oversimplifying something here?

IMO, the fact that neutrinos of different flavors come from Leptons of different sizes, and the fact that conservation of Lepton laws also apply to these interactions, makes it hard for me to understand how this data can be considered "strong" evidence of neutrino oscillation, or even neutrino transformation (one time transition to a new type).

If the authors had used a known and controlled transmitter and witnessed an actual neutrino transformation take place at the reciever, then I would have more confidence in their claim of finding "direct evidence of neutrino flavor transformation". As it is, the data that is being used as evidence to support this claim is "indirect" evidence at best, and can only be considered evidence if you put faith in current solar theory, *and* also in flavor oscillation at the particle level. IMO, the conclusions they come to do not seem to be based on "direct" evidence of neutrino oscillation under controlled conditions, but only on an indirect assumption that current solar theory is accurate and that the hypothesis they are trying to prove is true. It seems like we have to take two things for granted here, not one, and one of the things we have to take for granted is the very hypothesis they are attempting to demonstrate.

 

[jtbell]

If the Leptons are different scales in size, and there is a presumed mass difference between the various neutrinos, aren't we back to violating the conservation of energy laws by claiming they change mid flight from one rest mass state to another,

A neutrino does not change its mass when it oscillates. It changes its flavor (lepton type, i.e. e, mu, or tau). A particular neutrino may be created as one flavor and later on interact (be detected) as a different flavor. However, if we could measure the production and detection processes accurately enough to determine the neutrino's mass by conservation of energy and momentum, we would find the same mass at production and at detection.

There are three flavors of neutrinos, and three masses. The masses are not associated one-to-one with the flavors. A \nu_e has a certain set of probabilities of having each of the three masses. This is not the same as saying that there are three kinds of \nu_e's, with different masses! Each \nu_e is a quantum-mechanical superposition of the three mass states.

A \nu_{\mu} has a different set of probabilities for the same three masses. A \nu_{\tau} has yet another set of probabilities for those masses.

In order to understand neutrino oscillations, you have to understand superposition of states in quantum mechanics.

but also aren't we violating the conservation of Leptons rule by having them "change" as well?

Yes, neutrino oscillations "break" the concept of separate conservation of the individual lepton numbers (electron number, muon number and tau number, if you like).

 

[Michael Mozina]

Yes, neutrino oscillations "break" the concept of separate conservation of the individual lepton numbers (electron number, muon number and tau number, if you like).

http://hyperphysics.phy-astr.gsu.edu/hbase/particles/parint.html#c3

This isn't simply a "concept" we are attempting to overturn however, rather this is a conservation "law" of particle physics. It would be one thing if we could demontrate where two "laws" came into direct conflict. This conflict would make one of these laws "questionable". In this case however, we have what amounts to faith in a solar "theory" being used to attempt to overturn a known conservation "law" of particle physics. In cases where laws come into conflict with theory, it is customary to abandon the theory, not abandon the law.

As I said earlier, it is not as through we have observed this transformation under controlled conditions. Instead this SNO paper is based upon faith in current solar theory, something that is far less understood than particle interections that have been studied up close and personal for many decades. I see no logical reason to believe that a theory should be used as evidence to overturn a law. That is putting the cart before the horse IMO.

 

[jtbell]

As I said earlier, it is not as through we have observed this transformation under controlled conditions.

Results from such experiments, using neutrino beams from accelerators, are starting to come in:

http://www-numi.fnal.gov/

 

[Michael Mozina]

http://www.fnal.gov/pub/presspass/press_releases/minos_3-30-06.html

Sending a high-intensity beam of muon neutrinos from the lab's site in Batavia, Illinois, to a particle detector in Soudan, Minnesota, scientists observed the disappearance of a significant fraction of these neutrinos. The observation is consistent with an effect known as neutrino oscillation, in which neutrinos change from one kind to another.

It will take me a while to read through and digest the material that has been presented, particularly the Minos data and the papers Carl presented. I want to be fair and thurough.

The quote above from the press release however is a good example of what I meant earlier when I expressed concern that "missing" neutrinos are equated with "oscillation", when scattering/absorbtion processes could also explain "missing" neutrinos.

We are at least on the right track with the MINOS data in controlling the transmission source in these experiments. That much is very encouraging.

 

[SpaceTiger]

In cases where laws come into conflict with theory, it is customary to abandon the theory, not abandon the law.

This is overwhelmingly silly. Conservation laws are themselves a part of theories. The only reason they get the title "law" is because they are used as simple guidelines for deciding the outcome of interactions (much like Newton's Laws are used to decide the outcome of mechanics problems). Conservation of lepton number is a prediction of the standard model of particle physics, a theory which has now been shown to be at least partially wrong.

 

[Michael Mozina]

This is overwhelmingly silly. Conservation laws are themselves a part of theories. The only reason they get the title "law" is because they are used as simple guidelines for deciding the outcome of interactions (much like Newton's Laws are used to decide the outcome of mechanics problems). Conservation of lepton number is a prediction of the standard model of particle physics, a theory which has now been shown to be at least partially wrong.

First of all, let me be clear about my position on this issue. Based on the papers that Carl and others have referenced for me, I am in fact "open" to the possibility that neutrinos "oscillate". Neutrinos however may not "oscillate" at all, but rather they may 'decay' along the way or "change" based on some specific interaction with a particle. Neutrinos may not change flavor all, but rather they may be deflected and absorbed between the transmitter and the reciever. I remain open minded toward all these possibilities.

It seems however that there is what I would call "undue enthusiasm" on the part of "some" astronomers to claim that neutrinos "oscillate" in spite of the seeming violation of known laws of particle physics. The onus of responsibility to prove neutrino oscillation occurs to the exclusion of all other options is on the researchers that make this claim. I am simply looking at this issue "skeptically" just as I would skeptically examine any scientific claim. If their data excluded all other possibilities and their interpretation violated no known "laws" of physics along the way, I'd have no problem with their "oscillation" hypothesis.

There is however a "standard" and accepted practice in science as it relates to the order of presidence between "laws" and "theories". The "accepted" practice is that when theories violate known "laws", the theory is thereby falsified by this conflict. That is typically they way all theories are falsified in fact.

In the case of the SNO paper however, the "laws" of particle physics were said to be falsified based on current solar "theory" and based on current neutrino mass and oscillation "theories". That is exactly backwards from typical and accepted scientific practice. This claim is therefore an "exceptional" claim, and as such, this claim requires "exceptional evidence". So far I've not seen any "exceptional" evidence to justify this claim, though admittedly I've not been through the Minos data thuroughly yet. What I have read suggests that this team has not "ruled out" other so called "exotic" possiblities like decay and scattering/absorbtion. Note that there is a distinct difference between a "missing" (as in scattered/absorbed) neutrino and a "changed" (decayed) neutrino and an "oscillating" neutrino. There are at least three ways to explain "missing" neutrinos.

At the moment, the Minos data does seems to provide evidence of "missing" neutrinos, but that is not even technically evidence of detecting a "changed" neutrino, let alone evidence of "oscillating" neutrinos. As I said, I remain open to the possibility that neutrino flavors "change" or even "oscillate". I'm personally more comfortable with the concept of "change" over "oscillation", but both options remain on the table. Where I have a problem is "assumption" that a "law" of physics is invalid because of a data conflict with a "theory". That is not standard scientific practice, and IMO, there simply isn't enough data (yet) to support such a position.

Normally under a circumstance where a theory violates a law, we then claim the theory is falsified. In this case we are trying to claim the "law" is falsified by a theory.

 

[SpaceTiger]

There is however a "standard" and accepted practice in science as it relates to the order of presidence between "laws" and "theories". The "accepted" practice is that when theories violate known "laws", the theory is thereby falsified by this conflict. That is typically they way all theories are falsified in fact.

Nope. Theories are falsified by observation/experiment, not other theories. If it turns out, after studying it more carefully, that a theory predicts something that has already been falsified by experiment (say, non-conservation of energy in the Newtonian limit), then one can usually dismiss it without making new observations. Neutrino oscillations had not been experimentally tested prior to the first solar neutrino detections, so it couldn't be ruled out that the standard model of particle physics (along with the predicted conservation of lepton number) was wrong.

 

[CarlB]

Dear Michael Mozina,

The experimental evidence shows that the probability of detecting an electron neutrino is a function of distance, and that the function is typically an oscillatory one with the intensity of detected neutrinos going up and down as a function of distance. That in itself should be pretty convincing.

Like I said before, the mystery disappears when you think of the neutrinos as \nu_1, \nu_2 and \nu_3, in their mass eigenstates. Instead, the mystery, such as it is, is why neutrinos are not emitted in mass eigenstates. But none of the other particles are emitted in mass eigenstates so it shouldn't be much of a surprise when the neutinos aren't emitted that way either. Neutrino oscillation is built on pretty much the same principles that "explain" interference between a photon and itself in the 2-slit experiment.

What I'm saying is that neutrino oscillation is a very fundamental part of quantum mechanics and trying to reinterpret the evidence for it is unlikely to work out, UNLESS you are willing to also reinterpret quantum mechanics in general.

The concept of particles being emitted not on their mass shell (so that momentum and energy are not conserved) is a very fundamental part of field theory. Field theory is said to be the most accurate theory ever implemented by man with measurements of the g-2 of the electron now matching theory to something like 20 decimal places of accuracy.

If you want to also throw that away, and you want someone to listen to your ideas, you're going to have to first find some other theory that makes the same predictions.

It's not that I'm at all unsympathetic to the possibility that quantum mechanics needs to be replaced. In fact, I've been saying the same thing for years. But without a theory to replace it, the fact that the theory we have is, well, a bit rough around the philosophical edges, is not interpreted (by very many physicists) as evidence that the theory is wrong.

I worked on this problem for 3 years, but got constant complaints that my mathematics (i.e. Clifford algebra) was too complicated. Eventually I got around to working out consequences for the lepton masses. I eliminated all the difficult to understand "adult mathematics" and the resulting paper got some small amount of attention. My paper:
http://www.brannenworks.com/MASSES2.pdf

extended an empirical relation by Yoshio Koide, who wrote a paper referencing mine here:

http://www.arxiv.org/abs/hep-ph/0605074

And now I'm busily working on the next paper, which will put the adult mathematics back in. If you think that modern physics is crazy, I agree with you completely. But the practitioners are stunningly arrogant, quite certain that they are in possession of the truth, quite certain that amateurs can provide no useful commentary on the subject and are deeply uninterested in our opinions on this. You will get nowhere by pointing any of this out to them.

What I'm trying to say here is that instead of complaining about the darkness, why don't you try to light a candle?

Carl

 

[Michael Mozina]

Dear Michael Mozina,

The experimental evidence shows that the probability of detecting an electron neutrino is a function of distance, and that the function is typically an oscillatory one with the intensity of detected neutrinos going up and down as a function of distance. That in itself should be pretty convincing.

That is convincing evidence that "something" is occurring as a function of distance. Whether that "something" is scattering, absortion, decay or oscillation remains an unknown to me at this time. I personally would lean toward scattering since I have no desire to go outside the confines of laws of particle physics or Quantum Mechanics.

Like I said before, the mystery disappears when you think of the neutrinos as \nu_1, \nu_2 and \nu_3, in their mass eigenstates. Instead, the mystery, such as it is, is why neutrinos are not emitted in mass eigenstates. But none of the other particles are emitted in mass eigenstates so it shouldn't be much of a surprise when the neutinos aren't emitted that way either.

Your links are slow reading but they are very insightful and helpful in understanding a mathematical model to explain the oscillation hypothesis. I still have a long way to go before I feel "comfortable" with the idea, but at least I grasp the basic ideas a bit. I'm willing to let go of the conservation of "mass" concerns I had about this change based on what I've read so far. That math seems to work out, provided we envision the neutrino as having multiple wave forms. I'm more concerned about lepton conservation laws.

Neutrino oscillation is built on pretty much the same principles that "explain" interference between a photon and itself in the 2-slit experiment.

Actually however, there is quite a big difference here since we are violating particle "laws" related to lepton conservation, whereas no such violation is required to explain interference patterns in photons.

What I'm saying is that neutrino oscillation is a very fundamental part of quantum mechanics and trying to reinterpret the evidence for it is unlikely to work out, UNLESS you are willing to also reinterpret quantum mechanics in general.

How exactly do you "know" that neutrino oscillation is a "very fundamental" part of QM? The way I see it, we're are still looking for a way to rule out scattering and decay from oscillation at this point. First you would need to demonstrate to me that we've done this much before you could claim that neutrino oscillation occur, let alone suggest that neutrino oscillation is fundamental to QM in any way. I think you are "assuming" this point, rather than demonstrating this point. Photons are massless. Neutrinos are not massless. There are greater limits on particles with mass, and lepton conservation is one of those limits. That is why we have 'forbidden' decay possibilites.

The concept of particles being emitted not on their mass shell (so that momentum and energy are not conserved) is a very fundamental part of field theory.

But this is in the realm of "particle theory" where particles are assigned specific resting masses. Electrons have a specific resting mass compared to the mass of a proton. Evidently neutrinos have mass as well. Even if we allow for "flavor changing", we must conserve total energy, since that was the basis for suggesting that a neutrino exists in the first place.

Field theory is said to be the most accurate theory ever implemented by man with measurements of the g-2 of the electron now matching theory to something like 20 decimal places of accuracy.

Ok, but how does field theory explain the lepton conservation law violation?

If you want to also throw that away, and you want someone to listen to your ideas, you're going to have to first find some other theory that makes the same predictions.

It's not that I'm at all unsympathetic to the possibility that quantum mechanics needs to be replaced. In fact, I've been saying the same thing for years. But without a theory to replace it, the fact that the theory we have is, well, a bit rough around the philosophical edges, is not interpreted (by very many physicists) as evidence that the theory is wrong.

I think we're talking past one another here just a bit. I'm not suggesting we toss out QM, or conservation laws, or any laws of physics, including particle physics. I'd rather work *inside* these laws and theories rather than outside of them. As I see things "flavor transformation" are a violation of lepton conservation laws. Although I am very confident in the data sets in both the SNO experiements and the Minos experiments, I'm willing to look for "other ways" to explain the data sets that do not violate any known laws of particle physics. I have no need to fixate or concentrate on any explanation for these data sets that does violate any known laws of physics. Since oscillation is the only explanation that requires that lepton laws are invalid, I would be less inclined to consider that explanation over "scattering" or decay processes.

I worked on this problem for 3 years, but got constant complaints that my mathematics (i.e. Clifford algebra) was too complicated. Eventually I got around to working out consequences for the lepton masses. I eliminated all the difficult to understand "adult mathematics" and the resulting paper got some small amount of attention. My paper:
http://www.brannenworks.com/MASSES2.pdf

extended an empirical relation by Yoshio Koide, who wrote a paper referencing mine here:

http://www.arxiv.org/abs/hep-ph/0605074

And now I'm busily working on the next paper, which will put the adult mathematics back in. If you think that modern physics is crazy, I agree with you completely. But the practitioners are stunningly arrogant, quite certain that they are in possession of the truth, quite certain that amateurs can provide no useful commentary on the subject and are deeply uninterested in our opinions on this. You will get nowhere by pointing any of this out to them.

I'm convinced from the "dumbed down" versions I've read that the math works out as it relates to mass. I do not see how it conserves conservation of lepton orientation laws. I think that's my only beef to date with any of the math I've seen.

What I'm trying to say here is that instead of complaining about the darkness, why don't you try to light a candle?

Carl

I hear you on this point. I would say there probably is a way to explain the Minos data in terms of scattering related to energy states. I'd say that math is bit over my head at the moment, but I think that would be a more productive avenue than debating interpretations of data sets at a theoretical level only.

 

[CarlB]

That is convincing evidence that "something" is occurring as a function of distance. Whether that "something" is scattering, absortion, decay or oscillation remains an unknown to me at this time. I personally would lean toward scattering since I have no desire to go outside the confines of laws of particle physics or Quantum Mechanics.

When you look for the number of neutrinos of a given flavor as a function of distance from the source you find that as the distance increases, the number you detect goes down (which is compatible with scattering absorption, decay and oscillation) and goes up (which I think is compatible only with oscillation), depending on just how far you are from the source.

If neutrino oscillation were outside the confines of the laws of particle physics or quantum mechanics, believe me, someone would have noticed it by now.

The fact that neutrinos have a flavor basis and a mass basis that are distinct is an old idea but one that didn't have to be explored until it became known that neutrinos do, in fact, have mass. But the same concept was present in the standard model dating back to the Cabibbo angle.

In addition to neutrinos having a different flavor basis from mass basis, the same can be said of the quarks. In the literature, the flavor basis for quarks is denoted by a prime, as in d', s' and b' or u', c', t'.

You see, which type of quark you choose to have two different bases, the up quarks (u,c,t) or the down quarks, depends on your preference only. For a good explanation of this, see the book by Chen, "Quarks, Leptons and Gauge Fields", which was the text I learned from so many years ago. The usual preference you see is to keep the up quarks with a single basis and let the down quarks have two different bases. With that choice, the quarks are written {u,c,t,d,s,b,d',s',b'}. The conversion from {d,s,b} to {d',s',b'} is by the CKM matrix, which dates to 1963:
http://en.wikipedia.org/wiki/CKM_matrix

The same thing can be said about the leptons. Instead of treating the charged leptons as having a flavor basis identical to their mass basis, and the neutrinos as having two bases, we could just as easily reverse the situation and let the charged leptons have two bases and keep the neutrinos as described with a flavor basis equal to their mass basis.

The current situation is that the leptons are \{e,\mu,\tau,\nu_1,\nu_2,\nu_3,\nu_e,\nu_\mu,\nu_\tau\}, with the MNS matrix showing how to convert between the two bases for the neutrinos, but one could just as easily keep only one set of neutrinos and split the charged leptons into a mass basis and a flavor basis.

These choices were made for historical reasons and there is no reason whatsoever in the math to choose one over the other. Also what I'm saying here is that the violation of flavor conservation was already present in the quarks (and was known to great accuracy for decades) so it wasn't too much of a surprise to see it also present in the leptons. If anything, the addition of neutrino mass (and therefore neutrino oscillations) has made the standard model more simple. The particles are more consistent now.

The only law which is getting violated is lepton family conservation, which is a pretty small law. The equivalent conservation law for baryons was already known to be violated. Here is an easy to read explanation:
http://en.wikipedia.org/wiki/Flavour_(particle_physics)

Carl

 

[Michael Mozina]

When you look for the number of neutrinos of a given flavor as a function of distance from the source you find that as the distance increases, the number you detect goes down (which is compatible with scattering absorption, decay and oscillation) and goes up (which I think is compatible only with oscillation), depending on just how far you are from the source.

Which data specifically are you referring to where flavors "increase" over distance? Do you mean they increase in terms or raw numbers of hits or simply percentages relative to other types of neutrinos? We might have different energy states of neutrinos being scattered/absorbed at different rates, which may change "percentages" over a distance but it should result in fewer actually numbers of neutrinos received as we increase the distance.

On the other hand, some neutrinos may be more sensitive to the matierals they pass through than others. Increases in terms of percentages of relative neutrinos isn't necessarily a problem as it relates to scattering rates, whereas an increase in raw detections would be a different issue. I'm not sure which you are suggesting is the case here.

Even in this case an absorption/emission process that involves a one time change in "flavor" could not be eliminated as the "cause" for this change.

If neutrino oscillation were outside the confines of the laws of particle physics or quantum mechanics, believe me, someone would have noticed it by now.

Well, I'm sure that others have "noticed" that there is a lepton conservation particle physics law that is being violated. Like all debates, I'm sure I'm not the only one to notice this apparent problem. Here is the way I see things:

If we are going to throw lepton conservation laws of particle physics out the window, then wouldn't we expect to see this violation from the very start? We should be able to see and measure change over distance in any of the possible senarios that we are considering. Shouldn't we expect to see "forbidden" reactions violated immediately if lepton conservation laws are not actually applicable to these interactions?

If there are forbidden emissions from the outset, then what "causes" this violation to occur once the emission enters the quantum streams? Is it an internal decay process, an internal oscillation process, or something related to absorption and/or scattering?

Even in particle physics, there are laws and specifically conservation laws that are used to guide particle "theory", and used to determine which particles emissions are possible and which are not. This is one such "law". If the "guideline" is wrong, then why don't we see this violation immediately? If we don't see this violation immediately, how do we determine if this is purely an "internal" conversion process as opposed to a QM 'interaction' with the outside world?

The fact that neutrinos have a flavor basis and a mass basis that are distinct is an old idea but one that didn't have to be explored until it became known that neutrinos do, in fact, have mass. But the same concept was present in the standard model dating back to the Cabibbo angle.

The early "excitement" about neutrinos having mass came about through early experiments that provided evidence to suggest that muon neutrinos are more "massive" than electron neutrinos. Based on the various lepton sizes, that does logically makes sense. Since a Tau lepton is nearly 3500 times the size of an electron, I can understand how a Tau Neutrino could also contain more mass than both of the other flavors of neutrinos.

In any scenario we might use to explain the neutrino data sets, we *must* obey at least the laws of conservation of total energy, since that was the point of adding neutrinos in the first place. Creating a single "maga-multiple-wave particle" out of a single neutrino has it's own set of problems related to explaining different masses for different neutrinos. In essense you are suggesting that they do *NOT* have different masses afterall, but a "total mass" that is based on three different masses and contains all three masses! Now an electron neutrino has to carry the mass of three masses/waves, not just one! In essense we're now suggesting that there really isn't a "single" resting mass for any neutrino, and this sort of throws the first evidence right out the window from my perspective.

The only law which is getting violated is lepton family conservation, which is a pretty small law. The equivalent conservation law for baryons was already known to be violated. Here is an easy to read explanation:
http://en.wikipedia.org/wiki/Flavour_(particle_physics)

If it's a "small" law that is getting violated, why are their forbidden decay possibilities, and why aren't we noticing this violation immediately, right at the transmitter?

 

[CarlB]

Which data specifically are you referring to where flavors "increase" over distance? Do you mean they increase in terms or raw numbers of hits or simply percentages relative to other types of neutrinos?

The number of hits increases in absolute number of "raw hits". What was not there at all at short distances, begins to appear. And then that flavor disappears again, and then it reappears again. Furthermore, this happens repeatedly.

Even in this case an absorption/emission process that involves a one time change in "flavor" could not be eliminated as the "cause" for this change.

Let's see... The neutrino detector experiments generally give good information on the direction of travel of the received neutrino. It would be rather difficult to explain how a scattered beam of flavor changed neutrinos managed to keep traveling in the same direction. Especially if you're going to ascribe a different mass to the different flavor neutrinos (which is not quite the way that the standard model is put together by the way).

If we are going to throw lepton conservation laws of particle physics out the window, then wouldn't we expect to see this violation from the very start? We should be able to see and measure change over distance in any of the possible senarios that we are considering. Shouldn't we expect to see "forbidden" reactions violated immediately if lepton conservation laws are not actually applicable to these interactions?

Lepton number is conserved in neutrino oscillation, what you meant to write was "lepton flavor conservation" sometimes called "LFC". Conservation laws appear when experiments seem to show that something is conserved, and then they disappear when experiments show otherwise. In the case of lepton flavor conservation, the effect is suppressed by the low masses of the neutrinos, so the effect is difficult to see.

An intuitive way of explaining this is to note that the neutrino masses are very very small. Thus they typically travel at extremely high speeds, very close to the speed of light. At such high speeds, their clocks (proper time) run very slow so they don't have a lot of time available to do interesting things.

The quarks are much heavier, and therefore slower, and so their mixing is much easier to see (and like I said, this dates back to 1963 in the theoretical literature, which was motivated by experimental observations).

Even in particle physics, there are laws and specifically conservation laws that are used to guide particle "theory", and used to determine which particles emissions are possible and which are not. This is one such "law". If the "guideline" is wrong, then why don't we see this violation immediately? If we don't see this violation immediately, how do we determine if this is purely an "internal" conversion process as opposed to a QM 'interaction' with the outside world?

Like I said before, if you have a clue on how to write down an alternative explanation that explains the data, write it down. But there is a heck of a lot of data and it is going to be kind of difficult to explain. I'm hardly the poster child for believing in the standard model of particle physics, but I have no doubt about these things.

In any alternatives to the standard model, the difficulty is in the details. My hope for redoing this stuff is based on deriving the standard model itself from a very small number of very simple (deeper) first principles. That way instead of having to redo all the calculations of the standard model (which is so successful), I can subsume them into the deeper theory.

The early "excitement" about neutrinos having mass came about through early experiments that provided evidence to suggest that muon neutrinos are more "massive" than electron neutrinos. Based on the various lepton sizes, that does logically makes sense. Since a Tau lepton is nearly 3500 times the size of an electron, I can understand how a Tau Neutrino could also contain more mass than both of the other flavors of neutrinos.

This really isn't the way that these things are described in the current literature. The flavor neutrinos: the electron neutrino, muon neutrino and tau neutrino do not have masses in the sense that a particle like an electron has a mass. The neutrinos that do have exact masses are mixed from combinations of the flavor neutrinos. And as I mentioned before, exactly the same situation has been present with the quarks for 43 years, slightly longer than half the time that quantum mechanics has been in existence.

In any scenario we might use to explain the neutrino data sets, we *must* obey at least the laws of conservation of total energy, since that was the point of adding neutrinos in the first place.

Quantum mechanics hasn't had conservation of energy for "virtual" particles since the early 1940s. The calculations for neutrino oscillation are done as virtual particles. In fact, if you'll read Alexei Smirnov's notes, you will see that they can sometimes treat neutrinos "as if" they were on their mass shell. But mass shells are approximate things. Neutrino masses are very small, so that's a very thin shell.

In essense you are suggesting that they do *NOT* have different masses afterall, but a "total mass" that is based on three different masses and contains all three masses! Now an electron neutrino has to carry the mass of three masses/waves, not just one! In essense we're now suggesting that there really isn't a "single" resting mass for any neutrino, and this sort of throws the first evidence right out the window from my perspective.

The three mass eigenstate neutrinos, \nu_1, \nu_2, \nu_3 have exact masses. The "electron neutrino" you're talking about is a mixture of these neutrinos. If you don't like thinking about particles that carry mixtures of masses, then you need simply conclude that there is no such thing as an "electron neutrino". In fact, this is the way I prefer to think about it, as it is compatible with Bohmian mechanics.

Thinking about it this way, the emission of an electron neutrino gets replaced by the emission of a set of three neutrinos with three different masses. Each of these propagates separately. Each of them has (more or less) some chance of interacting with an electron, some chance of interacting with a muon and some chance of interacting with a tau. (I'm ignoring the differences between particles and antiparticles here for simplicity.)

So when you see an electron knocked loose by the incoming neutrino, was the incoming neutrino of type 1, 2 or 3? The answer is that you cannot tell, unless you make an explicit measurement of the incoming neutrino's mass, because quantum mechanics requires that all possible ways of making an interaction be added up (i.e. sum the Feynman diagrams), and only then are probabilities computed.

This fact, that ALL the Feynman diagrams contribute to an amplitude before the amplitude is converted (squared absolute magnitude) is the essential mystery of quantum mechanics and is also present in things like the two slit experiment (recall that Feyman said that the complete mystery of QM lies in just the 2 slit experiment).

If it's a "small" law that is getting violated, why are their forbidden decay possibilities, and why aren't we noticing this violation immediately, right at the transmitter?

Neutrinos are very light, so they tend to fly off before you get a chance to anything odd with them.

I think you're gradually beginning to "see the elephant". Quantum mechanics is an ugly subject, but this long predates neutrino oscillations. What is going on here is the essential mystery of QM, how it is that the photon travels down two paths at the same time. In this case, it is three neutrinos that get emitted at the same time.

Instead of two paths taken by the same particle, the essential mystery of QM is here being expressed in three paths that are taken by three different particles, namely the three different mass neutrinos, and yet they interfere with each other (and therefore produce oscillations).

Now in Bohmian mechanics, one supposes that only one of those three neutrinos was actually emitted. However, the two that were not still contribute to the "guiding wave". In the Many-Worlds interpretation, I suppose the three neutrinos are emitted in three different universes, which somehow interfere with each other. The result is that in one universe, the interaction was by a type 1 neutrino, in another it was type 2, etc., and in some other universe there was no interaction at all.

I think that this example is a great way of explaining quantum mechanics. Yes, the elephant is strange.

Now I could put all this into a context where it would make sense (and is no longer a mystery at all), but to do this, I'd have to rewrite pretty much everything you know about physics. As a start, you might consider how you would go about designing a universe if you were God. If you allow only waves, then things tend to flatten out. To get sharp things, so that you can arrange for a universe populated by moral creatures, you need to have matter defined in some sort of point-like manner.

But to get point like objects to interact is very very hard. The classical solution is to postulate fields that act at a distance, but these require that one install a bit too much magic in your universe for me to understand. For example, you would have to have two different types of objects in your universe, matter and waves, which is an extra complication. What God did was figure out how to get the whole thing done with just (point like) matter. And to do it, he had to mess around with time a little.

Carl

 

[jtbell]

If it's a "small" law that is getting violated, why are their forbidden decay possibilities, and why aren't we noticing this violation immediately, right at the transmitter?

When you produce (say) a muon-neutrino, it takes time for the probabilities of it interacting as an electron-neutrino or a tau-neutrino to deviate from their initial values of zero. So if you were to detect a neutrino immediately after it was produced, you wouldn't observe any oscillation! In "ordinary" accelerator-based neutrino experiments, the distance between the production site and the detector is not zero, but nevertheless short enough that the neutrinos don't have enough time or distance to oscillate enough for the effects to be visible against the inevitable "background" of interactions that mimic the ones that you're looking for, but really aren't.

During the 1980s, many accelerator-based neutrino experiments analyzed their data to search for neutrino oscillations. I did one such analysis as my Ph.D. dissertation. Nobody found anything, but they were able to set limits on key parameters that determine the size of neutrino-oscillation effects. The parameters deduced from the current successful neutrino oscillation experiments are of course consistent with those limits.

 

[Michael Mozina]

The number of hits increases in absolute number of "raw hits". What was not there at all at short distances, begins to appear. And then that flavor disappears again, and then it reappears again. Furthermore, this happens repeatedly.

Well, that phenomenon also happens repeatedly with photons with only a single wave function, as interference patterns emerge. I'm not sure that phenomenon is an insurmountable hurdle for the the single wave (scattering) option, however it does seem to suggest that the particles are not simply decaying into another type. That phenomenon would seem to favor oscillation over a one time decay.

I will try to respond to the rest of your post later today as things settle down here at work. I want to express my appreciation for the time and effort that you, jtbell, ST and others have put into this discussion. Even if we ultimately "agree to disagee", I certainly appreciate the time that has been spent to carefully answer all my questions. That has been extremely helpful and very much appreciated.

 

[Michael Mozina]

Let's see... The neutrino detector experiments generally give good information on the direction of travel of the received neutrino. It would be rather difficult to explain how a scattered beam of flavor changed neutrinos managed to keep traveling in the same direction.

I will break my response into a few parts since there are several issues being discussed here, and the posts are getting rather lengthy.

If is is "ok" to view the neutrino as one particle with three wave states of mass, then it would be equally approrpiate to treat all individualised neutrinos as individualized particles/waves that can be sensitive to "distance" as it relates to detection. I do not think we can use an apparent "oscillation" in detection rates with distance as an automatic guarantee that all waves are located inside the same particle. In otherwords the detection rate of a tau neutrino may be a function of the tau wave, and the muon detection rate determined by the muon wave in the muon neutrinos, etc. If the detection likelikehood changes with the individualized wave function of the neutrinos, then I think the results would still be consistent with observation. You seem to be suggesting that wavefunction observation can only be consistent with a "single" particle with three different states, instead of three particles with three different wave forms. I'm not sure we can make that leap of faith.

Especially if you're going to ascribe a different mass to the different flavor neutrinos (which is not quite the way that the standard model is put together by the way).

Well, the idea here is that neutrinos are the "leftover" bits of matter/energy that contain and conserve the "leftover" kinetic and momentum from various decay processes. When we talk about a muon decay, there is only so much total energy that can be "leftover" from such a decay. In a Tau decay however, being more massive particles to begin with, it's entirely possible that there is more "leftover" total energy from a decay process of a Tau particle. I'm open to these leftover masses being "close" but not the same or being quite different. There is some logic to believing that since their are various sizes associated with these different particles and decay processes, that the different neutrino masses relate directly to the different sizes of the parent particles.

In a "combined" neutrino view, you have one particle carrying *all* the mass from all three kinds of particles within the same "grouping", whereas I would simply separate the groups of waves into individual particles with separate wave functions (related to the size of the parent lepton. I would suggest that neutrinos are more prone to detection at different locations based on the arrangment the internal neutrino wave at the location of the detector. I would not think that much of the math would necessarily be all that different, but particles would have to be treated as separate waveforms with detection rates determined by the internal wave function of that flavor of neutrino.

 

[CarlB]

If is is "ok" to view the neutrino as one particle with three wave states of mass, ...

As far as I know, no one is doing this, so I don't know where you get the idea that it is "ok". When a neutron decays, it emits one neutrino. Our problem is that it is very difficult for us to determine the mass of that neutrino. We do know is that there could only be one neutrino emitted, but we cannot tell which mass it had (in general). For simplicity, instead of trying to keep track of this sort of detail, the usual method is to call this neutrino an "electron neutrino", but if you demand that particles have sharp masses, then there is no such particle.

Now there is a way that we could be sure which neutrino was emitted. If the amount of energy involved in the decay was so small that there was not enough to create either of the two heavier neutrinos, then, yes, you'd know exactly which neutrino was emitted (from energy considerations), and it would be the light one.

There is a physical situation where this effect is seen (or you might say, expected to be seen), and that is double beta decay. In double beta decay, a single beta decay is forbidden on energy conservation grounds, but two simultaneous decays is allowed. There is a possibility that such a decay could be neutrinoless. The experimental situation is currently a matter of a bit of a nasty academic debate. A good source of links is here:
http://www.nu.to.infn.it/Neutrinoless_Double_Beta_Decay/

My reason for being interested in this is that it is one of the few experiments where the absolute masses of the neutrinos (rather than differences between their squares) can be measured.

... then it would be equally approrpiate to treat all individualised neutrinos as individualized particles/waves that can be sensitive to "distance" as it relates to detection.

Yes, but you're going to have to explain why it is that distance just happens to cause one neutrino type to disappear exactly as much as the other neutrino types appear. In short, this is a tough row to hoe.

Well, the idea here is that neutrinos are the "leftover" bits of matter/energy that contain and conserve the "leftover" kinetic and momentum from various decay processes. When we talk about a muon decay, there is only so much total energy that can be "leftover" from such a decay. In a Tau decay however, being more massive particles to begin with, it's entirely possible that there is more "leftover" total energy from a decay process of a Tau particle. I'm open to these leftover masses being "close" but not the same or being quite different.

It's not the mass that is required to be conserved, it is the energy. Mass can be converted into energy according to Einstein. So a neutrino with mass 0.05 eV can take away any amount of energy so long as that amount is greater or equal to 0.05eV.

Let's look at it from the point of view of neutron decay. A neutron (in empty space) decays with a time constant of 20 minutes. The reason that the decay is energetically favored (or at least not forbidden) is that the mass of the neutron is greater than the total of the masses of the proton, electron plus the neutrino. Let us figure it out with the latest data from the Particle Data Group ( http://pdg.lbl.gov/2005/tables/bxxx.pdf http://pdg.lbl.gov/2005/tables/lxxx.pdf ).

\begin{array}{rcc}<br /> \textrm{Particle}&amp;\textrm{Mass (MeV)}&amp;\textrm{error}\\<br /> \textrm{neutron}&amp;939.56536 &amp;\pm 0.00008\\<br /> \textrm{proton} &amp; 938.27203 &amp;\pm 0.00008\\<br /> \textrm{electron}&amp;0.51099892&amp;\pm 0.00000004\\<br /> \textrm{neutrino}&amp;0.00000010&amp;\pm 0.00000010\end{array}<br />

In the above, I've put an arbitary neutrino mass of 0.1 eV. In reality, nobody knows the neutrino masses. Well, I do have my ideas (see http://www.brannenworks.com/MASSES2.pdf for my latest guess), but we do know that all three of the neutrino masses are somewhere around the number given, and probably considerably less.

Summing up the proton, electron and neutrino masses, we get 938.78302902 +- 0.00008 (notice that the neutrino masses get lost in the error bars of the proton mass which is also much larger than the error bars of the electron mass), which is smaller than the neutron mass by 0.78233098 +- 0.00016. Thus when a neutron decays, the amount of change in mass is so much larger than any of the neutrino masses that the concept that mass is conserved cannot place any restriction on which neutrino is emitted. (That is, any of the three neutrinos is possible).

Now, by the laws of QM, one must add together all the ways that a process can take place before computing absolute values and getting a probability. In the case of oscillations and the like, the way we tell that a (anti) neutrino was emitted was by absorbing it. Perhaps the absorbtion is by the conversion of a proton to a neutron. The same sorts of mass differences would apply to this process, so again, we would be unable to distinguish which mass neutrino was involved.

Since we cannot distinguish which mass neutrino was the one involved, we must add up all the possible ways for the reaction to proceed. In this case, the reaction is the conversion of a neutron to a proton and an electron and a "something" at the source, and the conversion of a proton to a neutron and a positron (or an electron is absorbed) at the other end. Such a reaction cannot specify which mass neutrino was exchanged. Accordingly, by the laws of QM, we must sum the complex numbers associated with all three ways it could happen, and then take the absolute value of that complex number.

Note that in this way of describing the situation there is no oscillation per se. Instead, what you have is an interference between the three different mass neutrinos that could have been emitted and absorbed.

Now the neutrino masses are so small that we can see that it is always going to be very difficult for us to tell which of them we are dealing with. Any process where a light neutrino is emitted and absorbed can also be thought of as a process where a midweight or a heavy neutrino was absorbed. Their masses are so very light.

So instead of talking about the three neutrinos with sharp masses, physicists talk about the three neutrinos characterized by the conversion of electron, muon and tau. In this basis, there is no longer sharp masses involved, but the loss in accuracy is so very small that it doesn't matter. And in this basis, the neutrinos oscillate (instead of interfering).

I think your questions have been very good at digging out exactly what is going on in this process. Thanks for making me go through it. I think my understanding of the neutrinos has increased in that I now appreciate that the flavor neutrinos are not the way that they should be looked at. It is the massive neutrinos that are fundamental.

Carl

 

[Michael Mozina]

Thank you Carl for a very interesting and informative discussion. I can't say that I agree at this point that neutrinos change flavor in mid flight, but I do at least see where you coming from and many of my original objections have been addressed. I still see no specific data that would lead me to believe that the three wave forms of mass are combined into one neutrino rather than just assuming that the position of the wave may affect our ability to detect them at different distances. I do at least however have a much better understanding of the concept, and I very much appreciate your time and effort and the efforts of everyone that participated in this discussion. Thanks.

 

[Michael Mozina]

http://www.yale.edu/opa/newsr/07-04-12-05.all.html

Hey Carl, I was wondering what you thought of the new MiniBooNE data, and whether or not you are still convinced that lepton conservation laws are being violated?

 

[moonstroller]

Is there a nutrino transmitter?