Non-vanishing U(e3) and cos 2 theta(23) from a broken Z(2) symmetry
Aug, 2004
26 pages
Published in:
- Nucl.Phys.B 713 (2005) 151-172
e-Print:
- hep-ph/0408123 [hep-ph]
Report number:
- UWTHPH-2004-19,
- OCHA-PP-244
View in:
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Abstract: (Elsevier)
It is shown that the neutrino mass matrices in the flavour basis yielding a vanishing U e 3 are characterized by invariance under a class of Z 2 symmetries. A specific Z 2 in this class also leads to a maximal atmospheric mixing angle θ 23 . The breaking of that Z 2 can be parameterized by two dimensionless quantities, ε and ε ′ ; the effects of ε , ε ′ ≠ 0 are studied perturbatively and numerically. The induced value of | U e 3 | strongly depends on the neutrino mass hierarchy. We find that | U e 3 | is less than 0.07 for a normal mass hierarchy, even when ε , ε ′ ∼ 30 % . For an inverted mass hierarchy | U e 3 | tends to be around 0.1 but can be as large as 0.17. In the case of quasi-degenerate neutrinos, | U e 3 | could be close to its experimental upper bound 0.2. In contrast, | cos 2 θ 23 | can always reach its experimental upper bound 0.28. We propose a specific model, based on electroweak radiative corrections in the MSSM, for ε and ε ′ . In that model, both | U e 3 | and | cos 2 θ 23 | , could be close to their respective experimental upper bounds if neutrinos are quasi-degenerate.Note:
- 28 pages, 12 figures, Some discussions are revised, references are corrected, Conclusions are unchanged
- 14.60.Pq
- symmetry breaking: Z(2)
- parametrization
- neutrino: mixing angle
- neutrino: mass
- mass: hierarchy
- electroweak interaction: radiative correction
- perturbation theory
- CP: violation
- neutrino: Majorana
References(91)
Figures(12)