[LEAPSECS] preprint about timekeeping for neutrino experiment

[Zefram]

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 

|uncertainties.

|

|best

|

|Carlo


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?

-zefram