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A What was the explanation of OPERA superluminal neutrinos?

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  1. Dec 27, 2015 #1
    When I first heard about the OPERA apparent superluminal results on the measurement of neutrinos speed, I tried to locate an explanation using all the possible relativistic effects. All were too small to account for a difference of 18 meters of virtual distance among photons and neutrinos.
    Then I realized that the effect could be non-relativistic. I called it «The Sagnac satellite effect». They were using GPS satellites to track times. If one assumes that somehow in the calculations they didn't take into account the time it takes for a light ray to reach the lab from the satellite, it turns out that there is a difference which is not only of the same order of magnitude than expected, but also close to the 18 meters figure.
    A back-of-the-envelope calculation uses this:

    d = v_e * h / c * cos (theta)

    where v_e is the Earth rotation speed (almost linear if only a few nanoseconds are taken into accout), h is the height of GPS satellite and theta is the mean latitude of the center of the segment connecting Gran Sasso and CERN.
    v_e = 464 m/s
    h = 20.000 km
    theta = 44°

    Thus d ~ 23 meters.


    Is it possible that a loosely tied switch could have turned off the correction needed for accounting this Sagnac effect when computing arrival times?
    I am a little puzzled because relativistic effect were orders of magnitude different, and however this effect is not of the same order but close to the value. Is it just a big coincidence?
     
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  3. Dec 27, 2015 #2

    mfb

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    They took this into account (and the effect is much smaller, keep in mind that both CERN and Gran Sasso are rotating in a similar way, and the effect depends on the satellite position so it is not a constant distance difference). The loose cable just prevented a proper clock synchronization, so different clocks recorded different things.
     
  4. Dec 27, 2015 #3
    Yes, the calculation uses only a single satellite and a mean position, also rectilinear movement instead of spherical coordinates and circular motion. It was just that I thought that the correction for the combined effect could have been masked due to the faulty wire. As for both locations rotating, the effect has just to do with time signals take to tragel each satellite-ground path. If you do not take Earth rotation into account you get a 20 meters difference or 90 nanoseconds time shift, which was the difference among neutrinos and light. Even I thought of a computer bug which did not calculate properly this part. The faulty wire is much more embarrasing, in my opinion.
     
  5. Dec 27, 2015 #4

    mfb

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    You don't get 20 meters. If the satellite is at 90 degrees to the rotation direction, the effect is zero (to first order). If the satellite is roughly at the horizon in the right direction, the travel time to Gran Sasso increases or decreases by 20 meters, and the travel time to CERN increases or decreases by nearly 20 meters as well, so clock synchronization is still better than 20 meters. Also, different satellite positions lead to different effect sizes (and directions), this would have been noted easily.
    Satellites at the horizon enhance uncertainties coming from atmospheric effects, so they were not used anyway.
     
  6. Dec 27, 2015 #5
    You are right, I had doubts about the diifferent positions of the satellites, number of them, etc. The consistency of the data troubled me with this plausible hypothesis. In any case, I don't see how a faulty wire could not lead to stronger and irregular perturbations, easily identified as noise.
     
  7. Dec 27, 2015 #6

    Jonathan Scott

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    The main problem wasn't a loose wire but rather a loose optical fibre connector. I think that meant that a pulse signal was much weaker than intended, causing triggering to be delayed well past the leading edge and resulting in the clock at the transmitting end being a few nanoseconds behind the GPS time being used for reference. There's a Wikipedia page on the subject (which I haven't read in full but appears to support this explanation): Faster-than-light neutrino anomaly
     
  8. Dec 27, 2015 #7
    Thanks for the reference, I read it but still cannot understand the details. It is my suspect that I may be somehow right at the end: if the time corrections are of the same order than the Sagnac satellite effect because there are contributions of several satellites, it is plausible that a faulty optical fiber could distort results in a magnitude similar to that exposed, with the close value just being a mere coincidencem However, if we were talking of other relativistic effects not being,corrected, many orders of magnitude different, it would be a very big coincidence to be of the similar value than the results. Summariziing, I am bold fo claim that the failure in synchro was related, even if indirectly, with synchro somehow related to GPS satellites and thus with contribution to several Sagnac satellite effects.
     
  9. Dec 27, 2015 #8

    PeterDonis

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    These two statements do not go well together. If you can't understand the details, why would you think you may be "somehow right"?
     
  10. Dec 28, 2015 #9
    Just before Cern discovered the error they repeated the experiment/calibration with a greatly reduced packet size and published the exact same sized errors as they obtained with their original published experiment/calibration. I always thought it was unusual that the errors stayed exactly the same for both tests despite the reasons given.

    http://www.theguardian.com/science/2011/nov/18/neutrinos-still-faster-than-light?newsfeed=true
    It is a pity that they didn't published something like the NASA "Hubble Space Telescope Optical Systems Failure Report" to eliminate any misconceptions.

    https://www.ssl.berkeley.edu/~mlampton/AllenReportHST.pdf
     
  11. Dec 28, 2015 #10
    Because the data to be corrected were precisely those satellite effects, so that would explain, if the correction fails by software bug, optical fiber defect or anything else, that the correction would fail to apply and if it is on the correct order of magnitude, then no strange that the value coincides so close.
     
  12. Dec 28, 2015 #11

    mfb

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    There are many signal propagation delays that had to be taken into account, some of them are about 20 meters, even if the loose fibre would have let to the measurement ignoring one of them there is no reason to expect a specific one.
    The sagnac-like effect, as shown above, is significantly below 20 meters, and varies from satellite to satellite, contrary to the observation of the OPERA collaboration. We can rule this out.

    From the wikipedia page:
    Reference 22 is the most interesting one, the original is in German but there is a translation available: the details of the fibre connection influenced the synchronization of two clocks, if the fibre was loose one clock was too late/early with respect to the other.

    "I don't understand it, therefore I'm convinced whatever I came up with is right" is never a good approach.
     
  13. Dec 28, 2015 #12

    Vanadium 50

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    I agree.

    MachPrinciple, is there any evidence whatsoever that could come from OPERA that would convince you that you are wrong? If so, what? If not, well, if not, can you really say you are doing science?
     
  14. Dec 28, 2015 #13
    Neutrinos they exhibit spontaneous chiral oscillations. This provides a temporal metric for the neutrino's reference frame. As such, time (relative to this frame) is not stretched to infinity, so neutrinos must travel at non-celerital speed. Certain interactions of neutrinos occur in a temprorally asymmetric way, therefore the neutrinos travel in negative time direction towards the future as all sub-luminal entities.
    This not only provides neutrinos with a sub-luminal speed, but also a non-zero rest mass.
     
  15. Dec 28, 2015 #14
    I am not doing science. It was speculation all the time. I could not pretend to peer-review an experiment which is outside my scope, knowledge and means. Simply I have always found the coincidence very curious. Nothing else. As for the effect, it must be rutinarily be taken into account, whatever its name if it has one (Sagnac effect would be a little different here). I will not suggest that they are masking the real error by anoth
     
  16. Dec 28, 2015 #15

    Vanadium 50

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    Well, since you have your answer, and refuse to believe it, maybe it's time for the thread to be closed.
     
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