Left-right symmetric model with $\mu \leftrightarrow \tau$ symmetry

Abstract

We analyze the leptonic sector in the left-right symmetric model dressed with a $(Z_2{)}^3$ discrete symmetry which realizes, after weak spontaneous breaking, a small broken $\mu \text{lra}\tau$ symmetry that is suggested to explain observable neutrino oscillation data. $\mu \text{lra}\tau$ symmetry is broken at tree level in the effective neutrino mass matrix due to the mass difference ${\tilde{m}}_{\tau }\ne {\tilde{m}}_{\mu }$ in the diagonal Dirac mass terms, whereas all lepton mixings arise from a Majorana mass matrix. In the limit of a small breaking we determined ${\theta }_{13}$, and the deviation from the maximal value of ${\theta }_{ATM}$, in terms of the light neutrino hierarchy scale, $m_3$, and a single free parameter $h_s$ of the model.

Comments: 9 pages, 4 figures. Title changed and we have added one new section: CP phase contribution. Minor corrections and references updated. Published version