S 3 flavor symmetry and leptogenesis
Institute for Theoretical Physics, Kanazawa University, 920-1192, Kanazawa, Japan
2 Institut für Physik, Universität Dortmund, Otto-Hahn-Str.4, 44221, Dortmund, Germany
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Revised: 2 August 2005
Published online: 25 November 2005
We consider leptogenesis in a minimal S 3 extension of the standard model with an additional Z 2 symmetry in the leptonic sector. It is found that the CP phase appearing in the mass matrix of the left-handed neutrinos is the same as that for the CP asymmetries responsible for leptogenesis. Because of the discrete S 3 x Z 2 flavor symmetries, the CP asymmetries are strongly suppressed. To obtain a realistic size of the baryon number asymmetry in the universe, we therefore have to assume that resonant enhancement of the CP asymmetries takes place, and that three degenerate right-handed neutrino masses of O(10) TeV are present.
© Springer-Verlag, 2006