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The neutrino matrix: why are there three of everything?

The SuperKamiokande detectorOctober 1, 2012 The Guardian UK

Last week’s results from the Daya Bay neutrino experiment were the first real measurement of the third neutrino mixing angle, θ13 (theta one-three). There have been previous experiments which set limits on the angle, but this is the first time it has been shown to be significantly different from zero.

Since θ13 is a fundamental parameter in the Standard Model of particle physics1, this would be an important measurement anyway. But there’s a bit more to it than that.

Neutrinos – whatever else they might be doing – mix up amongst themselves as they travel through space. This is a quantum mechanical effect, and comes from the fact that there are two ways of defining the three types of neutrino.

 

Continue reading The neutrino matrix: why are there three of everything?

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