I’ve been pouring through the neutrino paper from Archiv-x. It is an honest paper. They had their stuff right, as far as they could tell, before they released it. This is not hack work. That said, there are a lot of pieces to this measurement that invite (and in this case demand) very great scrutiny.

The short form of it is:

Neutrinos are produced by particle collisions at CERN in a way that points them in the direction of the OPERA facility some 730 km away. Those particle collisions produce more than just neutrinos. At the same instant the neutrinos are created, other are particles created with them. Ironically, this would not happen if relativity were not true. They smack into detectors at the CERN facility. This gives a time of birth for the neutrinos. Using GPS and atomic clocks time is synchronized with the neutrino detectors at OPERA. From looking at the clocks, there is a measurement of flight time.

A very careful program was undertaken to get as accurate as possible a measure of the detectors’ distance from CERN at OPERA.

If you have the distance and the time of flight, you divide and get the speed.

The neutrinos fly through the Earth’s crust. Since only interact through the weak force, they rarely interact at all. Vast numbers of them from the sun and astronomical sources are going through you right now. Since they don’t interact, they pass right through.

There are a number of places to look more closely.

1. Are these really the neutrinos they are looking for? A lot of neutrinos come out of CERN. This experiment demands knowing very well that a given neutrino born at CERN was the same one that came down range to OPERA and that OPERA was not looking at a neutrino born earlier. That is an issue to be explored by going into the bowels of OPERA’s detectors, computer code and electronics.

2. Are there any systematic delays in the electronics that the researchers missed? If the time measurement is off by even a little this result is off. The people at OPERA certainly looked very hard to find such errors and report a systematic errors that are small compared to their findings. It is perfectly possible for very good scientists to do very good work and still miss something honestly.

I personally think that the an error will be found in case one or case two.

3. How good really is the distance measurement? Again this is something that will have to be scrutinized.

4. Perversely, and I think that it is likely the GPS and distance measurement people accounted for it, but perversely, are their time measurements sufficiently accurately taking General Relativistic effects from the Earth’s gravitational fields into account? GR predicts that gravitational fields will effect time measurements. For a mass the size of the Earth the effect is very small, but these are very precision measurements. It would be charming if it was Einstein himself reaching from the grave to kill this.

There is going to be a very careful look of every aspect of the experiment by the larger particle experiment community.

Back in the day I worked particle theory. I was never a particle experiment guy, and there is an awful lot to know (as in an experimental particle Ph.D’s worth) before one can meaningfully comment in more detail about how to make sure the particle experiment guys did this right. I don’t know nearly enough about the intricate details of their detectors, their code or their methodology to really comment on what might have gone wrong in any more detail than in the broad strokes I have already written.

I am very confident from the overwhelming strength of relativity working everywhere else (and being part of how we know neutrinos are produced in the first place) that there will be a systematic error found in the experiment. Relativity is so strongly verified by so many other things that I believe the proper question is not “did relativity go wrong”, but rather, how can we make even better neutrino experiment?