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Neutrino oscillation


Strange

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This is not something I understand well, so I'm not sure if these questions make much sense...

The Wikipedia page says:

Quote

Neutrino oscillation arises from a mixture between the flavor and mass eigenstates of neutrinos. 

But I don't fully understand the explanation. (https://en.wikipedia.org/wiki/Neutrino_oscillation#Theory)

Is the oscillation between different flavours of neutrino something that happens to a single neutrino, or is it a statistical thing that can only be observed among a number of neutrinos? 

I was made to think about this because of their different masses. So, if for example,  there was just one neutrino in the entire universe, would it still oscillate between flavours? But then its mass would change, which would seem to violate conservation laws. So does the oscillation depend on their being at least three neutrinos which share the masses and flavours, and we only see the change when we take a snapshot of the state by observing one of them?

Just got to this bit of the Wikipedia page: https://en.wikipedia.org/wiki/Neutrino_oscillation#Classical_analogue_of_neutrino_oscillation

Are the two pendulums here supposed to represent a pair of neutrinos that share the mass and flavour information?

Edited by Strange
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On 6/28/2018 at 12:22 PM, Strange said:

This is not something I understand well, so I'm not sure if these questions make much sense...

The Wikipedia page says:

But I don't fully understand the explanation. (https://en.wikipedia.org/wiki/Neutrino_oscillation#Theory)

Is the oscillation between different flavours of neutrino something that happens to a single neutrino, or is it a statistical thing that can only be observed among a number of neutrinos? 

I was made to think about this because of their different masses. So, if for example,  there was just one neutrino in the entire universe, would it still oscillate between flavours? But then its mass would change, which would seem to violate conservation laws. So does the oscillation depend on their being at least three neutrinos which share the masses and flavours, and we only see the change when we take a snapshot of the state by observing one of them?

Just got to this bit of the Wikipedia page: https://en.wikipedia.org/wiki/Neutrino_oscillation#Classical_analogue_of_neutrino_oscillation

Are the two pendulums here supposed to represent a pair of neutrinos that share the mass and flavour information?

I see lots of views, but no response... The two pendulums would exchange energy regardless their makeup, however the periods of oscillation would differ. If the spring were not connected to another pendulum there would be no interaction and nothing would change... Should be the same whether we are talking pendulums or neutrinos. As far as mass goes, do we separate mass and energy? The energy transfer between the pendulums could as easily be mass transfer between neutrinos.

Wow, Strange, you cannot help but assist me! This goes well with my last post in my latest topic!

Thx!

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A good question, Strange +1.

Butch I can't see anything objectionable in your post +1 to cancel the negative.

On 28/06/2018 at 5:22 PM, Strange said:

This is not something I understand well, so I'm not sure if these questions make much sense...

The Wikipedia page says:

Quote

Neutrino oscillation arises from a mixture between the flavor and mass eigenstates of neutrinos. 

But I don't fully understand the explanation

 

Strange, this is also beyond my knowledge of particle physics, but that Wiki article is self declared to be unfinished and in need of improvement.

Your quote starts with how it arises.

Stepping back a bit to finding out what it is

 

Quote

Wiki

Neutrino oscillation is a quantum mechanical phenomenon whereby a neutrino created with a specific lepton flavor (electron, muon, or tau) can later be measured to have a different flavor. The probability of measuring a particular flavor for a neutrino varies between 3 known states as it propagates through space.[1]

and

Quote

Wiki

In contrast, due to their larger masses, the charged leptons (electrons, muons, and tau leptons) have never been observed to oscillate.

As I understand things, the electron is (considered) an elementary particle so could not 'oscillate' in the proposed manner.
So although the statement is true why include it?

Equally the original statement of what is meant by oscillation does not include any reference to an essential requirement of oscillation, that of periodicity.

The maths presented has periodicity but not in time but over an energy range, which would be another one of these hilbert phase space oscillation (not waves) rather than a classical oscillator.

 

 

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57 minutes ago, studiot said:

As I understand things, the electron is (considered) an elementary particle so could not 'oscillate' in the proposed manner.
So although the statement is true why include it?

Neutrinos are also elementary particles. My understanding of that section was that the larger mass (or, more accurately, mass difference) between the charged leptons means the oscillation is not observable. (But it isn't clear why.)

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24 minutes ago, Strange said:

Neutrinos are also elementary particles. My understanding of that section was that the larger mass (or, more accurately, mass difference) between the charged leptons means the oscillation is not observable. (But it isn't clear why.)

Do Physicists ask why?

:)

 

Anyway my first quick reading of the Wiki thought that as well, but if you read it carefully it does not actually say that mass is the cause, it could be taken to be implied, but Physics statements are preferably explicit rather than implicit.

But that is not the my main point, which is that elementary particles do not have quark type internal structure to support the kind of oscillation descibed, so it must be something else.

As I said, my knowledge is not good enough to say what. Perhaps Marcus or Mordred or the old reliable swansont.

And that is why I was not impressed by the article.

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1 hour ago, studiot said:

 The maths presented has periodicity but not in time but over an energy range, which would be another one of these hilbert phase space oscillation (not waves) rather than a classical oscillator.

There is a periodicity in time, they just didn't present it that way. They have shown the probability after traveling a length L, which depends on t and v, which of course means it depends on E.

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9 minutes ago, studiot said:

But that is not the my main point, which is that elementary particles do not have quark type internal structure to support the kind of oscillation descibed, so it must be something else.

 

Neutrinos do not have internal structure. 

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2 minutes ago, swansont said:

There is a periodicity in time, they just didn't present it that way. They have shown the probability after traveling a length L, which depends on t and v, which of course means it depends on E.

Thank you for the reply.

The explicit nature is in quark stark contrast with Wiki, which is why I asked for better information.

They also do not explain how that is an oscillation.

How is your t, v explanation different from the situation with my car which has a certain energy every t I fill the tank, but the t intervals may be variable and certainly do not constitute an oscillation, although I drive at a some speed v.

If you prefer consider a jet fighter with mid air refuelling to avoid the stopping and starting business.

1 minute ago, Strange said:

Neutrinos do not have internal structure. 

So it must be something else.

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2 minutes ago, studiot said:

Thank you for the reply.

The explicit nature is in quark stark contrast with Wiki, which is why I asked for better information.

They also do not explain how that is an oscillation.

The state changes. You have a time-varying probability of having a different neutrino.

2 minutes ago, studiot said:

How is your t, v explanation different from the situation with my car which has a certain energy every t I fill the tank, but the t intervals may be variable and certainly do not constitute an oscillation, although I drive at a some speed v.

If you prefer consider a jet fighter with mid air refuelling to avoid the stopping and starting business.

You fill your tank on occasion. It will depend on how far you have driven, and how fast you drive (which affects gas mileage). So you could graph the dependence. But I don't see how you can say that filling your tank does not have a t dependence. It's not an oscillation, because what is supposed to be oscillating?

 

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41 minutes ago, swansont said:

The state changes. You have a time-varying probability of having a different neutrino.

You fill your tank on occasion. It will depend on how far you have driven, and how fast you drive (which affects gas mileage). So you could graph the dependence. But I don't see how you can say that filling your tank does not have a t dependence. It's not an oscillation, because what is supposed to be oscillating?

 

Gosh I didn't say it does not have a t dependence, quite the reverse.

I said it was not periodic (although it could be) and therefore not an oscillation.

I am aware of the sin2 term in the Wiki, but not sure what the physical significance of the angle is, as it is a probability plot.

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Neutrino oscillations are oscillations of the mass term and the flavor eugenstates. In essence a neutrino can be emitted as one flavor but oscillate to another flavor eugenstate. This involves the neutrino mixing matrix MNS which I won't attempt to latex the form of lol. However in essence it is a series of phase changes involving the mass eugenstates and the flavor eugenstates.

Here is a simpler article than many I have read in the past covering this.

https://warwick.ac.uk/fac/sci/physics/staff/academic/boyd/stuff/lec_oscillations.pdf

Edited by Mordred
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31 minutes ago, studiot said:

Gosh I didn't say it does not have a t dependence, quite the reverse.

I said it was not periodic (although it could be) and therefore not an oscillation.

If you looked at the time dependence rather than energy dependence, it would be periodic. IOW, pick an energy and look at time dependence instead of length. L = vt. There's a sin term in the equation. The amplitude is going to look like sin(kt)

31 minutes ago, studiot said:

I am aware of the sin2 term in the Wiki, but not sure what the physical significance of the angle is, as it is a probability plot.

It's an amplitude for the superposition. They have to be 1 or smaller, and the sum of the squares must equal 1. 

If the superposition is a|A> + b|B>, where a is the amplitude for state A and b is the amplitude for B

 a^2 + b^2 = 1 i.e. the total probability of being in one of the states is 100%. So they use sin and cos (see the matrix U in the link), which automatically works, and refer to it in terms of the angle.

 

 

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Correct section 0.2 has a simplified explanation in the link above, see section 0.2. Section 0.4 has a more complete example of the mixing by giving an example of the two flavor oscillations under the mathematical treatment.

Edited by Mordred
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Well yes I understand that these are also leptons with very different mass, but similar dipole moments.

But I don't understand what bearing that has on electrons and whether or not electrons have flavors.

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1 hour ago, Strange said:

Some particles, such as protons and neutrons, are composite. 

 

1 hour ago, swansont said:

Having internal energy states, which implies a composite particle.

Thx!

Strange, you should note that the spring in the pendulum example is not needed. You can easily demonstrate this, suspend two pendulums from a rod and anchor the rod any way you wish. Start one pendulum swinging and it will transfer its energy to the other.

Moral of the story is, if there is any way for an oscillating entity to transfer its energy it will.

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1 hour ago, Butch said:

Moral of the story is, if there is any way for an oscillating entity to transfer its energy it will.

You are right about the pendulum example, the spring is only needed becasue the pendula are shown fixed to rigid foundations.

But have you given any thought to the chicken and egg situation?

That does the oscillating entity transfer its energy or the other system extract it?

5 hours ago, studiot said:

Well yes I understand that these are also leptons with very different mass, but similar dipole moments.

But I don't understand what bearing that has on electrons and whether or not electrons have flavors.

Looking up flavours on Wiki is even more confused than the neutrino article.

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1 hour ago, Butch said:

 Strange, you should note that the spring in the pendulum example is not needed. You can easily demonstrate this, suspend two pendulums from a rod and anchor the rod any way you wish. Start one pendulum swinging and it will transfer its energy to the other.

Moral of the story is, if there is any way for an oscillating entity to transfer its energy it will.

It will transfer the energy because something is acting like the spring. In the example, the spring represents all mechanisms for transferring energy. Physics example are often idealized like this.

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6 minutes ago, swansont said:

It will transfer the energy because something is acting like the spring. In the example, the spring represents all mechanisms for transferring energy. Physics example are often idealized like this.

Any elastic entity is a spring isn't it? Electrons, atoms, molecules, rubber bands?

Edited by Butch
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5 hours ago, studiot said:

Well yes I understand that these are also leptons with very different mass, but similar dipole moments.

But I don't understand what bearing that has on electrons and whether or not electrons have flavors.

Those are the flavors of the other leptons. It's just that with neutrinos we gave them all the same last name.

https://en.wikipedia.org/wiki/Flavour_(particle_physics)  

1 minute ago, Butch said:

Any elastic entity is a spring isn't it?

They can often be modeled that way. Many things in physics are modeled as harmonic oscillators or springs.

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