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Symmetries, Large Leptonic Mixing and a Fourth Generation

Joaquim I. Silva-Marcos
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Abstract

We show that large leptonic mixing occurs most naturally in the framework of the Sandard Model just by adding a fourth generation. One can then construct a small $Z_4$ discrete symmetry, instead of the large $S_{4L}\times S_{4R}$, which requires that the neutrino as well as the charged lepton mass matrices be proportional to a $4\times 4$ democratic mass matrix, where all entries are equal to unity. Without considering the see-saw mechanism, or other more elaborate extensions of the SM, and contrary to the case with only 3 generations, large leptonic mixing is obtained when the symmetry is broken.

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Joaquim I. Silva-Marcos. 2002-06-19. Symmetries, Large Leptonic Mixing and a Fourth Generation. https://doi.org/10.1088/1126-6708%2F2002%2F12%2F036

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