1111.6262 (Adrian Palcu)

Dimension-five effective operators in electro-weak SU(4)xU(1) gauge
models    [PDF]

Adrian Palcu

We prove in this letter that the electro-weak SU(4) x U(1) gauge models with
spontaneous symmetry breaking can offer a natural framework for generating
neutrino masses by simply exploiting the tree level realization of
dimension-five effective operators. The novelty of our approach resides in the
fact that the scalar sector needs not to be enlarged, since these operators are
constructed as direct products among scalar multiplets already existing in the
model. As an advantage, this procedure does not require additional Yukawa
coefficients in the lepton sector besides the ones coming from Standard Model.
The predictions in the most favorable case of our analysis are: no CP-phase
violation in the neutrino sector, \sin theta_13 = -0.1985 and the absolute mass
spectrum for left-handed neutrinos m1 = m2 = 0.03eV and m3 = 0.05eV .
Right-handed neutrino masses lie in the sub-keV region, independently of the
cut-off lambda. The latter introduces in the theory an intermediate scale
(however, more close to GUT than to SM) at about 10^12 GeV which is a crucial
ingredient for the left-handed neutrino phenomenology.

View original: http://arxiv.org/abs/1111.6262