It seems not so long ago I was writing an article on this blog about a new result from the OPERA experiment in which neutrinos were observed to travel faster than the speed of light. At the time I commented about how it could still be an error in the data.

Today the same group of experimentalists released an updated report in which they reduce one source of error and still see FTL neutrinos. One criticism of the first result was that the different in flight time of the neutrinos was approximately 60 nanoseconds, while the production of the neutrinos took longer than that to produce, and as such it was possible that the neutrinos were just produced a little earlier than expected and hadn't traveled faster than light.

The team has now reduced the production time to only 3 ns, and yet they still see the neutrinos arriving 60ns earlier than expected.However it still is controversial.

For example, since the original report was released last month, physicists have done related calculations as a method of checking the results: 
  • One of particular note is the time lapse between neutrinos and light arriving from the famous 1987 supernova. The two types of particles arrived a few hours apart, which was expected since supernovae release neutrinos a few hours or days ahead the photons of light. If neutrinos could travel as fast as this team suggests, then the neutrinos would have arrived several years earlier - and that did not happen.
  • On a slightly more technical note, it has also been noted that the Standard Model predicts the electrons will travel faster than light if neutrinos do, as a result of symmetry properties and the production of virtual particles. But electron speeds have been very carefully studied for decades and this is not the case.
  • And finally the result that I find most interesting is a measurement of the distance between the source of neutrinos and the detectors. It is a complicated calculation, but the end result is that a calculation of the distance using GPS satellites and including the effects of special relativity indicate that the neutrinos travel a shorter distance than claimed, and coincidentally should arrive 64ns earlier than originally claimed. So the OPERA team is proudly announcing a 60ns early arrival but others have argued that the neutrinos are expected to arrive 64ns early if the correct distance is used.
Obviously this is still a very exciting result, and one that will be studied in great detail. It has already inspired almost 100 papers to be submitted on possible exotic and mundane explanations. And so even if the result is eventually discredited, it will still impose some strict new constraints on new theories of exotic physics. And that is always a good thing for the scientific community!