[time-nuts] Opera coordinator has resigned

Tom Van Baak tvb at LeapSecond.com
Fri Mar 30 16:57:29 UTC 2012


Hi Javier,

Thanks very much for posting the link to the presentations.

For those of you who just want a summary of the resolution of
the "neutrino faster than light" problem, here's what happened:

1) For several years an optical cable connector was loose. I have
attached photos from pages 7 and 8 of the G._Sirri.pptx where
you can see the actual connector and waveforms, before/after.

2) They used a Vectron OCXO to generate timestamps within each
0.6 second measurement cycle. This oscillator was found to be high
in frequency by 0.124 ppm. Thus, depending on where within this
0.6 s interval the timestamp was made a timing bias of 0 to 74 ns
would occur.

Javier -- if you have contacts there, it looks to me like they forgot
to include OCXO frequency drift effects into their analysis. What
they did was compensate for linear time drift (which assumes a
fixed frequency offset). They call the 124.1 ns/s time drift "stable"
since 2008. What evidence do they have for this? We know that
OCXO will drift in *frequency* over time; the time drift is quadratic.
The time drift rate may be 124e-9 today, but it probably wasn't last
month or last year, etc.

/tvb

> There was a meeting in Gran Sasso on Wednesday. You can see some of
> the slides at http://agenda.infn.it/materialDisplay.py?materialId=slides&confId=4896
> 
> I found particularly interesting the ones by Maximiliano Sioli, where
> he explained the two mistakes found in the OPERA data acquisition
> chain and how, after correcting for their best estimate of their
> effects, the time of flight is compatible with a speed of c.
> 
> I saw the webcast of the event. Some people did give the OPERA
> spokesman a hard time, and he admitted to not having fully checked
> everything they could have. Ah well, everyone makes mistakes. There
> will be another run with neutrinos spaced by 100 ns in May. If all
> four experiments in LNGS give the same result this time, I suppose the
> case will be closed. It will also be very interesting to see the MINOS
> results.
> 
> In any event, from a time-nut point of view this is quite exciting. It
> is the first time neutrino speed is measured with this precision. I
> think this will pave the way for future experiments using precision
> geodesy and time transfer.
> 
> Cheers,
> 
> Javier
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