Here, watch this:
http://www.youtube.com/watch?v=FAivtXJOsiI
Light doesn't slow down, the more dense the medium the more light bends to make it through that medium...its speed is still the same
...and if the Earth is not as dense in an area as we think it is... that would cause the light to arrive faster than we planned on it getting there.
Again, If there are two particles of light traveling, and one goes through earth's gravity-well, to an outside observer, one particle is going slower than the other. If I look at them from the side, the one who's going through Earth's gravity appears to 'bend' `~._,~' vs ------. These particles of light are traveling the same distance, however to the outside observer one is 'slower' than the other. This has to do with a Mass' effect on Time, and speed is a function of time.
Therefor, if there is less mass than we believe, it's effect on time is going to be different than we think. Since speed is a function of time, and time is 'relative' (HEY THAT'S WHERE THAT THEORY'S NAME COMES FROM!!!), depending on where the observer/observation is taking place, your results could look 'interesting' especially if you're basing your numbers off of an educated guess, and not exact measurements.
...Also, since CERN is the only place capable of producing the energies needed to create this experiment, it cannot be peer reviewed, and thus would be a bogus claim scientifically.