General solutions for TM$_{1,2}$ mixing in the minimal type-I seesaw mechanism and phenomenological constraints to Yukawa matrix of neutrinos

Abstract

In this paper, we concisely represent the general solution for the TM$_{1,2}$ mixing in the type-I minimal seesaw mechanism and show phenomenological constraints of the Yukawa matrix of neutrinos $Y$. First, conditions of $Z_{2}$ symmetry associated with TM$_{1,2}$ restrict two complex parameters. In addition, three complex parameters are constrained from five phenomenological parameters (two neutrino masses $m_{i}$, the mixing angle $\theta_{13}$, the Dirac phase $\delta$, and the Majorana phase $\alpha$) and the overall phase. As a result, there is only one free complex parameter for $Y$, except for the right-handed neutrino masses $M_{1,2}$. For the TM$_{1}$ mixing with normal hierarchy, the symmetry condition is imposed only on $Y$, and the physical parameters depend on $M_{R}$. In other situations, the dimensionless parameters $(\theta_{13}, \delta$ and $\alpha)$ do not depend on $M_{R}$ but only on certain combinations of the components of $Y$.