$1/(M_{R})_{33}$ expansion of the type-I seesaw mechanism and partial $Z_{2}$ symmetry for TM$_{1,2}$ mixing

Masaki J. S. Yang

paper

$1/ (M_{R})_{33}$ expansion of the type-I seesaw mechanism and partial $Z_{2}$ symmetry for TM $_{1, 2}$ mixing

arXiv:2208.10000

Abstract

We consider an expansion of the type-I seesaw mechanism by the inverse of the 3-3 matrix element $1/ (M_{R})_{33}$ of the mass matrix of right-handed neutrinos $M_{R}$ . Conditions of such a situation are obtained for $M_{R}$ and the Dirac mass matrix $m_{D}$ . In this case, a partial $Z_{2}$ symmetry such as $S m_{D} P = \pm m_{D} P$ with a projection matrix $P = diag (1, 1, 0)$ leads to an approximate $Z_{2}$ symmetry by $S$ for the neutrino mass matrix $m_{ν}$ . Such a partial $Z_{2}$ symmetry is desirable in the context of unified theories because it allows hierarchical $m_{D}$ and the large mixing of $m_{ν}$ simultaneously.

9 pages

1/(MR​)33​ expansion of the type-I seesaw mechanism and partial Z2​ symmetry for TM1,2​ mixing

Abstract

$1/ (M_{R})_{33}$ expansion of the type-I seesaw mechanism and partial $Z_{2}$ symmetry for TM $_{1, 2}$ mixing