Sunday, August 23, 2009

only 3 generations

Cottingham and Greenwood give a good presentation of the argument for why there are only 3 generations of neutrinos. The argument comes from the predicted rate of decays of Z to invisible (i.e., neutrinos), compared with the experimentally measured rate. The plot on p. 128 is pretty striking. It makes you think that there really shouldn't be another neutrino beyond the 3 we know of.

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