[LEAPSECS] preprint about timekeeping for neutrino experiment

Zefram zefram at fysh.org
Tue Oct 4 07:04:03 EDT 2011

Fran?ois Meyer wrote:

>In my view the two clocks are just synced to each other as far as this experiment

>is concerned. That does not change the point about gravitation though.

I emailed Contaldi about the TTD, and I've just had this interesting
response from him:

Carlo Contaldi wrote:

|Dear Zefram


|thanks for the comments, I corresponded with the OPERA group and I agree

|that the TTD is not a moving clock as I interpreted. However it is used

|to calibrate a relative delay at both ends of the baseline using local

|reference frequency generators and these would be susceptible to time

|dilation effects as in the stationary part of my calculations.


|In addition the time scales over which they calculate the delays are

|vastly different from those used in the measurement and it is not clear

|at all that they have measured the noise on the relevant time scales.


|Effectively they are relying on the GPS signal at both ends being

|synchronised at < ns and this is what I find hard to believe,

|particularly on short time scales where atmospheric effects may induce a

|much larger uncertainty than they have accounted for.


|I also agree that their Euclidean analysis may also introduce further






So I think the state of play is: need more details from the OPERA team,
and there's a world of error budget haggling to come.

I couldn't figure out the operation of the time source system (local
caesium plus GPS plus other bits) from the diagram in the PTB tech note.
The details seem to matter quite a bit to the synchronisation. Does
someone here know the equipment, or recognise the configuration? TvB?


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