Eur. Phys. J. C (2006) 45: 465-475
https://doi.org/10.1140/epjc/s2005-02434-3

Theoretical Physics

S ₃ flavor symmetry and leptogenesis

¹ Institute for Theoretical Physics, Kanazawa University, 920-1192, Kanazawa, Japan
² Institut für Physik, Universität Dortmund, Otto-Hahn-Str.4, 44221, Dortmund, Germany

^* e-mail: araki@hep.s.kanazawa-u.ac.jp

Received: 28 April 2005
Revised: 2 August 2005
Published online: 25 November 2005

Abstract

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.