# Faster than light neutrinos conundrum solved?

Discussion in 'Physics & Math' started by prometheus, Feb 22, 2012.

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3. ### Farsight

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And here's a physicsworld report:

http://physicsworld.com/cws/article/news/48763

It mentions a CERN press release and two potential sources of error, one one way, the other the other. Can I mention that I wasn't impressed with The Einstein was wrong! headlines a few months back, so I'm not surprised by the latest developments. For reference see this old thread. I do think they were right to make the announcement though, and lay out the results of the experiment right or wrong rather than just sit on it because it didn't seem to fit with expectations. The paper itself played a straight bat, even if there was considerable media hype.

5. ### brucepValued Senior Member

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Measuring Time of Flight Using Satellite-Based Clocks
http://arxiv.org/abs/1110.2685

.... but they didn't acknowledge the mistake with the GPS. Now they had a loose connection over the course of all the runs? There's a huge list of authors on the CERN teams paper. Really 'Big Claim' including 10 nanosecond error bar.

7. ### Aqueous Idflat Earth skepticValued Senior Member

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For what it's worth, anyone who's worked with fiber optics will remember once or twice when the connector appeared to be properly polished and seated, yet somehow it turned out to misbehave. Also, for all the gadgets that are used to test the lines and calibrate the line delay, it can give a false sense of security just to get green light on a receiver.

It is a little odd though, that they let the cat out of the bag before confirming that it had claws. Especially for such a remarkable result.

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9. ### OnlyMeValued Senior Member

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I took a quick look at the linked article and the ArXiv paper it references? The ArXiv paper can be found here, Measurement of the neutrino velocity with the ICARUS detector at the CNGS bea. I am not sure the last word has been said on this issue. There are at least two issues I could not find a "direct" reference to.

The MINOS results mentioned were at far lower initial proton energy levels than those in the OPERA results late last year and the recent new test does not, at least directly state the initial proton energies of the new test.

It would seem that to put the issue to rest initial proton energies, is an issue that needs to be addressed. I have no idea why a clear statement of the new beam's energy level was not included in the paper. It is the kind of information that is generally included. Especially, while both the lower energies of the MINOS results and the high energies of the earlier OPERA results were, included in the new paper. It is difficult to believe this is nothing more than oversight, sice this is at least one of the potential issues for the earlier variation in the MINOS/OPERA results and conclusions.

Another issue is that since neutrinos are still considered to have a rest mass, even moving at the speed of light, which is the conclusion of the new test, should be an issue requiring some explanation. Though the 1987a supernova data suggests and supports, speed of light neutrinos, also. There is no way to know the initial energies resulting in neutrino emmision in the supernova case or how high initial enter energy levels may affect the final neutrino velocity...

I think it is still too soon to say the issue is settled. It is likely best to wait for the experiment to be rerun, by the OPERA group, where the conditions can be as close to the original experiment as possible and for MINOS to reproduce the experiment, at an entirely different accelerator/detector... Or for a more complete description of the initial conditions in the newer experiment.

10. ### rpennerFully WiredValued Senior Member

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If they measured the neutrinos to be consistent with the speed of light within 4 parts per million, this would put a lower bound on gamma to be 350.
If they measured the neutrinos to be consistent with the speed of light within 3 parts per million, this would put a lower bound on gamma to be 400.
If they measured the neutrinos to be consistent with the speed of light within 2 parts per million, this would put a lower bound on gamma to be 500.
If they measured the neutrinos to be consistent with the speed of light within 1 part per million, this would put a lower bound on gamma to be 700.
If they measured the neutrinos to be consistent with the speed of light within 1 part per 8 million, this would put a lower bound on gamma to be 2000.

Since it takes about 2.4 million nanoseconds for light to travel 731 km, I don't think this experiment says anything new about neutrino mass. I thought the detectors needed neutrinos good deal more energetic than 1 keV .

11. ### Pincho PaxtonBannedBanned

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Well I agree that I wrote solved too soon as well.

12. ### OnlyMeValued Senior Member

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I don't think it says anything about neutrino mass either. That reference in my post was almost a side question, that has been bugging me. (A particle with a rest mass and a velocity of c.)

What bothers me, is that while the paper does describe the initial energies involved for both the OPERA and MINOS experiments, I did not find any mention of the energies involved in this new experiment. It may have been assumed to be equivalent to the earlier CERN/OPERA experiment since CERN was the source, of the proton beam. This paper seemed to me to just present data and conclusions without the in depth, description of the experimental set up and control, seen for the other two.

Granted, these papers are difficult for me to work through. If in your reading you find that they did cover these issues and I just missed it or did not understand, perhaps you could translate or point out what I missed?

Even should that wind up not being an issue with only seven detected events, it would seem only to suggest that additional tests are needed.

By the way, while there is some romantic desire that FTL neutrinos be confirmed, as it would result in some exciting new times in theoretical physics, I have no personal investment either way.

13. ### rpennerFully WiredValued Senior Member

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With 7 events I don't think they can say very much about the energy of the detected neutrino events. (It's not a number, it's a distribution.) Neutrino beams exhibit wide spreads in energy because of the nature of electroweak interactions. But something in the range 3GeV to 30GeV is likely the answer based on past CERN-SPS to Icarus events.
http://arxiv.org/abs/1110.3763

Since a 3 GeV electron has a gamma factor of about 6000, and outside of the timing sensitivity of this experiment to detect as different than light, it's not meaningful to discuss the energies of the neutrinos when the energy-velocity relationship is essentially flat over the experimental range to experimental sensitivity.

Last edited: Mar 16, 2012
14. ### GustavBannedBanned

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wow
thats a lot of "associated crackpots"

15. ### OnlyMeValued Senior Member

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Thank you for the quick response. After reading the above and re-reading the recent paper, I realized that while I was talking about the initial proton beam energy levels, the paper was talking only about the neutrino energies.

I am assuming at this point the recent or new test is generating neutrinos with essentially the same initial proton energies as the eralier CERN/OPERA experiment. A tighter beem duration being the difference.

It is not infrequent that I have to read these papers several times to even get a reasonable glimpse of what they intend to present.

16. ### XoticaEveryday I’m ShufflinRegistered Senior Member

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From what I hear, independent experiments are being prepared at Fermilab (US) and at KEK (Japan).

17. ### CptBorkValued Senior Member

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On a slightly different topic, I've been thinking about the neutrino conundrum for a while and was curious about something:

If neutrino masses are responsible for their flavour oscillations, then Relativity would forbid them from travelling at lightspeed, correct? And if they couldn't travel precisely at $c$, that would in theory permit an observer to catch up to them and reverse their observed helicity, right? So in summary, if the Standard Model were extended to incorporate neutrino masses, wouldn't it also be forced to include right-handed neutrinos and left-handed antineutrinos?

18. ### rpennerFully WiredValued Senior Member

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That was my understanding: neutrino mass eigenstates are Dirac fermions. Neutrino flavor eigenstates are superpositions of the mass eigenstates.

19. ### discusfish99Registered Member

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Not to burst everybody's bubble who wants ftl travel like in star trek, i remember seeing these articles about it.