Neutrino Majorana masses and mixings can be generated from a dimension-5 operator within the standard model particle content. After a review of the mechanism of radiative enhancement of the mixing angle in a two-neutrino case, we consider three-flavor mass matrices of two-zero texture generated from such an operator and investigate the possibility of implementing the mechanism here. We observe that radiative magnification of only the solar angle is consistent with oscillation data on masses and mixings, and that too for nearly degenerate neutrinos, with two of them having opposite $\mathrm{CP}$ parities, while for hierarchical masses the mechanism does not work. In supersymmetry or in an extra-dimensional scenario the above features are qualitatively unchanged.

• Received 11 November 2002

DOI:https://doi.org/10.1103/PhysRevD.67.073004