Frédéric Grosshans links to a nice discussion by Matt Strassler The mumblings that begin a few months after the initial report, that a loose cable caused a timing chain error, have been accepted by the experimenters. In an edited press release (and probably in the peer-reviewed literature as well), all four of the neutrino experiments at Gran Sasso report results consistent with relativity. You have a few longer answers which were already updated, but here is a concise statement of the situation in mid-2014:Īn independent measurement by the ICARUS collaboration, also using neutrinos traveling from CERN to Gran Sasso but using independent detector and timing hardware, found detection times "compatible with the simultaneous arrival of all events with equal speed, the one of light." Update: This possibility excluded by a new experiment with 3 ns pulses. Furthermore, the pulses are quite long (10 μs), so an error in this analysis could easily be of the good order of magnitude. The timing itself is based on a quite elaborate statistical analysis. Errors in the statistical timing analysis I suppose an explanation along these lines would mean interesting new particle physics. However, the detectors were built to measure the oscillation, so I guess that the OPERA collaboration thought about it, and rejected it for whatever reason. Neutrino oscillation might, for example, then make early neutrino more detectable by the distant detector. It might be possible that the neutrino emitted early are not exactly the same as the one emitted late. The neutrinos are emitted on a 10.5 µs window, 175 times longer than the observed effect. Update: Rumors seems to tell that the boring explanation is the good one. If this would however end up to be the explanation, it would be quite boring. The distance seems to be known within 20 cm and the synchronisation seems to be within 15 ns (6.9 statistical and 7.4 systematic). The arXiv paper studied them, and seem to exclude it. Of course, the current list only contains biases which are unlikely, but less unlikely than a causality violation. As many physicists (including, I guess, many people from the OPERA collaboration), I think it will end like the Pioneer anomaly. I thought it might be a good idea to list the possible systematic biases which could lead xkcd's character to win his bet. A high level description of the problem is given here and a more detailed explanation of the investigation is here. Last (?) Edit: The "problem" is solved: it was mainly a problem in the timing chain, due to a badly screwed optical fibre.
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