[lutorm]

You didn't look at the webcast, did you? Someone asked this question and they said "no we took it into account in the sense that the clocks at CERN and Gran Sasso run at different speeds because they are at different elevations. However, that's only a 1e-18 effect and the signal is 1e-5.

[mrb]

I am talking about the presence of the gravitational field, not its difference between the 2 sites. Anyway, I calculated gravitational time dilation on Earth out of curiosity. It has an effect of only about 1e-9.