Flavor symmetry L{sub e}-L{sub {mu}}-L{sub {tau}}, atmospheric neutrino mixing, and CP violation in the lepton sector
- Scuola Internazionale Superiore di Studi Avanzati, Via Beirut 2-4, I-34014 Trieste, Italy and Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34014 Trieste (Italy)
The Pontecorvo-Maki-Nakagawa-Sakata neutrino mixing matrix is given, in general, by the product of two unitary matrices associated with the diagonalization of the charged lepton and neutrino mass matrices. Assuming that the active flavor neutrinos possess a Majorana mass matrix which is diagonalized by a bimaximal mixing matrix, we give the allowed forms of the charged lepton mixing matrix and the corresponding implied forms of the charged lepton mass matrix. We then assume that the origin of bimaximal mixing is a weakly broken flavor symmetry corresponding to the conservation of the nonstandard lepton charge L{sup '}=L{sub e}-L{sub {mu}}-L{sub {tau}}. The latter does not predict, in general, the atmospheric neutrino mixing to be maximal. We study the impact of this fact on the allowed forms of the charged lepton mixing matrix and on the neutrino mixing observables, analyzing the case of CP violation in detail. When compared with the case of exact bimaximal mixing, the deviations from zero U{sub e3} and from maximal atmospheric neutrino mixing are typically more sizable if one assumes just L{sup '} conservation. In fact, |U{sub e3}|{sup 2} can be as small as 0.007 and atmospheric neutrino mixing can take any value inside its currently allowed range. We discuss under which conditions the atmospheric neutrino mixing angle is larger or smaller than {pi}/4. We present also a simple seesaw realization of the implied light neutrino Majorana mass matrix and consider leptogenesis in this scenario.
- OSTI ID:
- 20708958
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 71, Issue 7; Other Information: DOI: 10.1103/PhysRevD.71.073002; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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