1. ## Neutrinos preceding radiation and the promise of exact measurements

(I did a cursory search for a discussion on the forum about the precise calibration of radiation and neutrinos over distance, but could not find such. Admins, please discard this post if it has already been discussed.)

Supernova SN1987A

The tantalizing evidence that the velocity of light is preceded by the greater speed of neutrinos is all over the news at the moment.

It would seem that we stand on the cusp of being able to precisely measure the distance of powerful bursts of energy, such as a nova.

I recall a few years ago that a burst of radiation from supernova SN1987A was preceded by a burst of neutrinos three hours before the radiation.

It follows that if we can produce a source of radiation emission such as that created by the OPERA international experiment, then we can calibrate the exact amount of time it takes light and neutrinos to get from point A to point B,
By calculating the time delay between light and neutrinos, we would know with considerable exactness the distance if a given emission.
Last edited by pzkpfw; 2011-Sep-29 at 03:52 AM. Reason: Image size

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If the 20ppm difference detected by CERN is true, then SN1987a was ~18ly away by this method.

First thing I did when I saw the first thread here was actually run the numbers. At 160000ly, the neutrino burst should have arrived 3 years beforehand.

3. Cool. Glad someone thought of it. I had a feeling some of the brighter members of the forum had. Your calculations create more puzzling questions than they solve, no?

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not really. Taking the CERN data as correct is very premature, and I doubt that anyone has checked to see if there was a neutrino burst from the that direction in 1984.

Even if the CERN data is correct, there is no telling if the velocity they calculated is a constant either. It is possible that the neutrino burst we think is the one from SN1987a and the CERN data is correct.

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Originally Posted by gfellow
Cool. Glad someone thought of it. I had a feeling some of the brighter members of the forum had. Your calculations create more puzzling questions than they solve, no?
Again, not really. You should also know that current models of supernova, combined with the properties of neutrinos, make a difference of several hours quite likely. Neutrinos escape immediately from the explosion near the center of the star. The explosion itself takes some time to break through and become visible. The exact time difference depends on the make up of the star, the radius of the star, the power of the explosion, etc.

6. Originally Posted by gfellow
Cool. Glad someone thought of it. I had a feeling some of the brighter members of the forum had. Your calculations create more puzzling questions than they solve, no?
It's the recent experiment that raises puzzling questions, but remember that the most likely answer is that there was a problem in the experiment somewhere.

7. Originally Posted by Van Rijn
It's the recent experiment that raises puzzling questions, but remember that the most likely answer is that there was a problem in the experiment somewhere.
Most likely. Still - the results could be confirmed, always a chance. IF this is the case, it ought to make for some considerable excitement.

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The phase velocity of electromagnetic radiation may – under certain circumstances (for example anomalous dispersion) – exceed the speed of light in a vacuum, but this does not indicate any superluminal information or energy transfer. It was theoretically described by physicists such as Arnold Sommerfeld and Léon Brillouin. See dispersion for a full discussion of wave velocities.
http://en.wikipedia.org/wiki/Phase_velocity

I don't know exactly the nature of the neutrino propagation. Neutrino doesn't contain a charge as other fermions built of quarks or leptons or photons (electromagnetic wave). Therefore its propagation is different in the vacuum containing the virtual particles and antiparticles.
What is a difference between the phase velocity of the photon and of the neutrino ?

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Photons are not charged either.

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Originally Posted by Shaula
Photons are not charged either.
Photons and neutrons are neutral but contain charged parts. You can create charged particles from neutron and photon (particle + antiparticle).
Neutrino is always neutral and it is not possible to create a charged particle from it. Therefore my question is: what is a difference between the distribution of the electromagnetic wave (photon) and weakly interacting neutrino ?
Both of them interact gravitationally.
A low energy photon of the 1 m wavelength has its uncertainty of the position about 1 meter. The absorber registers the information when the whole 1 m wave is absorbed.
What is the process of the absorption of the neutrino ? Does it has its wave ?

11. Originally Posted by czeslaw
Photons and neutrons are neutral but contain charged parts.
Neutrons are made up of charged components (quarks) but photons are not.

What is the process of the absorption of the neutrino ?
Neutrinos interact only via the weak force - this is why they are produced in beta decay.

Does it have its wave ?
All particles have a wave description.

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Originally Posted by Strange
Neutrinos interact only via the weak force - this is why they are produced in beta decay.
All particles have a wave description.
I repeat my question: what is a difference between the distribution of the electromagnetic wave (photon) and weakly interacting neutrino ?
The neutrino is a wave of what ?

13. Originally Posted by czeslaw
I repeat my question: what is a difference between the distribution of the electromagnetic wave (photon) and weakly interacting neutrino ?
I almost certainly can't answer but what do you mean by "distribution"?

The neutrino is a wave of what ?
My [limited] understanding is that in quantum field theory, every particle can be treated as a quantum of the associated field. The photon is the quantum of the electromagnetic field; the neutrino is the quantum of the "neutrino field".

That doesn't really seem to be much of an answer though; it just says that a neutrino is a neutrino. But on the other hand, I'm not sure we can say any more than that. A neutrino is just defined by the quantum numbers that a neutrino has....

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Originally Posted by czeslaw
I repeat my question: what is a difference between the distribution of the electromagnetic wave (photon) and weakly interacting neutrino ?
The neutrino is a wave of what ?
You are confusing bosons and fermions here as well. The neutrino is a fermion, the photon is a boson. The photon is therefore associated with a force. The neutrino is NOT the carrier particle associated with the weak force.

That is the major difference. Edit: Which means that the distribution of the fermionic neutrino is changed by a transform which exchanges a pair of particles while the bosonic photon wavefunction is not changed.

So the neutrino has no need to be 'associated' with any field other than the general neutrino field which is an alternative way of expressing the presence of a neutrino particle.

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Thank you Shaula. Indeed the photons are bosons and neutrinos are fermions and they obey the Pauli's exclusion principle.
It is a fundamental difference.
Since the 1980s, various experiments have verified that it is possible for the group velocity of laser light pulses sent through specially prepared materials to significantly exceed the speed of light in vacuum.
http://en.wikipedia.org/wiki/Group_velocity
May be the tiny particles like neutrinos may exceed the speed of light in a special condition of the group velocity ?
What do you think about it ?

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Any wave can have its group speed higher than its phase speed. And vice versa. Provided the conditions are right. You need an area of anomalous dispersion and a spread of frequencies in the input. The only obvious way to test your idea is to alter the energy spread of the injected neutrino pulse and see if it affects the measured speed. You would also, therefore, expect it to affect the different flavour neutrinos differently but I suspect that is a measurement way beyond our capabilities to perform.

I think they need to confirm the experimental results before we get too excited. Then they need to better explore variations of this effect. Then finally they need to rejig theory if there is a residua unexplained and repeatable effect.

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Yes. The distance between Geneva and Gran Sasso is 733 km. We don't know what the phase velocity or group velocity means exactly for the neutrino. We know how it works for photons which are bosons and it doesn't carry the information. There are performed many experiments which shows the non-locality of the entangled photons. How it works for neutrinos on a short distance ?
http://en.wikipedia.org/wiki/OPERA_experiment
The long distances observation of the Supernovae outburst shows almost the same velocity as the speed of light.
What exactly means a process of the oscillation of muon neutrinos to tau neutrinos in a local space of the 733 km ?

18. Originally Posted by czeslaw
Yes. The distance between Geneva and Gran Sasso is 733 km. We don't know what the phase velocity or group velocity means exactly for the neutrino.
I'm not sure of the relevance of this. Group and phase velocity only apply to classical wave propagation, not to individual particles. But they were not measuring individual particles anyway. It could apply to the bunches of neutrinos. But I think this is ruled out by the fact that, you would expect a dramatic change in amplitude and pulse shape neither of which were seen. Also, I believe it requires a variation in velocity with energy which was specifically looked for and not found.

There are performed many experiments which shows the non-locality of the entangled photons. How it works for neutrinos on a short distance ?
I don't see how entanglement could be relevant.

The long distances observation of the Supernovae outburst shows almost the same velocity as the speed of light.
Yes. (Although, the OPERA experiments also shows "almost the same velocity as the speed of light" ) If the neutrinos from the supernova had behaved the same way, they would have arrived about 4 years before the light.

What exactly means a process of the oscillation of muon neutrinos to tau neutrinos in a local space of the 733 km ?
I'm not sure what you are asking. However, the main objective of the OPERA experiment was to look at mu-tau neutrino oscillation.

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Current interpretation of the group velocity for a neutrino wavepacket is the particle speed. Maybe that needs to be modified to a front speed as has been done for light. That would allow the information transfer condition for relativity to still be met.

You seem to be posing a lot of questions without advocating anything - maybe you should take them to Q&A where people better qualified than me can answer more completely.

20. Originally Posted by Shaula
You seem to be posing a lot of questions without advocating anything - maybe you should take them to Q&A where people better qualified than me can answer more completely.
I'll make that official.

I would also appreciate no more responses to czeslaw's questions in this thread.

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Yes. It is not my thread and therefore I am posing the questions without advocating anything. I am sorry gfellow didn't answer these questions. Thank you Strange and Shaula for discussion. We have to wait for gfellow.