Needless to say, I've had a lot of questions coming my way regarding the recent neutrino results from OPERA. You'll notice that I've tried to refrain from making any kind of analysis and commentary on this thing. But it appears that my lack of response to it seems to be causing even more questions and prodding for me to say something.
Actually, I intend to. However, I need to know quite a bit more of what is going on beyond just what they had put down on their preprint. And being at a place where I have access to people who work at CERN (through the ATLAS collaboration), and people working on MINOS, provides me some advantage of talking to them and getting their feedback. But that takes time, because these people themselves are inundated with similar questions.
I'm saving more of my comments till later next week. That's when the MINOS people here will have a chance to make their presentation and comments on this result. However, just to wet your appetite, I will describe the common theme that has been running through many of the people I've spoken to.
A very important factor here is the pulse length. The proton beam that hits the target as about, what, microsecond pulse length. This beam collision with the target creates muons, etc. that will eventually decay and create the neutrino beam in that same direction. Now, it is assumed (with good reason), that the neutrino beam will ALSO have that same pulse length. So when the neutrinos are detected, one expect the same pulse length. It is from such observation that they deduce the speed of the neutrino, very much like measuring the group velocity.
The problem here is that, the proton beam itself is quite long. If one studies the beam dynamics, one can easily envision that the tail end of the proton beam might get affected by the kicker, and that can lead to the beam not having the exact pulse length as expected when it hits the target. This affect is a bit more difficult to find and detect, unlike, say, the electronics and timing, where one can change things to double check if one gets the same thing.
There's plenty of reasons to be skeptical of the result, as one should be, as of now. We just need to let the process work itself out. I'm pretty sure the folks at MINOS and T2K will be looking at this more closely. They hold the key to the independent verification/falsification of this observation, and they are the only ones that can do that. Jumping to conclusion right now and making speculative scenario of what would happen if this is true is highly and truly premature.
Zz.
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