15 June 2010

Neutrino v. Anti-Neutrino Discrepencies?

Fermilab investigators working on the MINOS experiment have found a 40% difference between neutrino and anti-neutrino oscillations, with a two standard deviation significance, in a result announced yesterday (in a press release).

There are reasons for skepticism. A difference would seem to imply that neutrinos and anti-neutrinos of the same flavor have different masses. Yet, every other known particle has precisely the same weight as its anti-particle. In short, it is probably a fluke. While a 5% chance of a statistical fluke wouldn't bother a social scientist, physicists expect about four standard deviations of certainty, particularly when a result is at odds with empirically well established prior theory.

But, since every anomalous result starts out being statistically insignificant, it is worth noting. If true, it will be one of those "who ordered that?" moments in the history of science.

Most plausibly it would involve some sort of CP violation. This would allow for a scenario in which neutrinos and anti-neutrinos have the same mass, but their oscillation frequencies are not the same because anti-matter would be disfavored relative to matter in some way.

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