Consequences of minimal seesaw with complex $\mu\tau$ antisymmetry of neutrinos

TL;DR

This paper explores a complex extension of $$ permutation antisymmetry in neutrino mass matrices, analyzing its phenomenological implications for neutrino mixing, neutrinoless double beta decay, and baryogenesis via leptogenesis.

Contribution

It introduces a novel complex $$ antisymmetry in neutrino mass matrices and studies its phenomenological consequences in the minimal seesaw framework.

Findings

Maximal Dirac CP phase predicted

Majorana phases are 0 or 

Bounds on right-chiral neutrino mass derived

Abstract

We propose a complex extension of $\mu\tau$ permutation antisymmetry in the neutrino Majorana matrix $M_\nu$. The latter can be realized for the Lagrangian by appropriate CP transformations on the neutrino fields. The resultant form of $M_\nu$ is shown to be simply related to that with a complex (CP) extension of $\mu\tau$ permutation symmetry, with identical phenomenological consequences, though their group theoretic origins are quite different. We investigate those consequences in detail for the minimal seesaw induced by two strongly hierarchical right-chiral neutrinos $N_1$ and $N_2$ with the result that the Dirac phase is maximal while the two Majorana phases are either 0 or $\pi$. We further provide an uptodate discussion of the $\beta\beta0\nu$ process vis-a-vis ongoing and forthcoming experiments. Finally, a thorough treatment is given of baryogenesis via leptogenesis in this scenario, primarily with the assumption that the lepton asymmetry produced by the decays of $N_1$ only matters here with the asymmetry produced by $N_2$ being washed out. Tight upper and lower bounds on the mass of $N_1$ are obtained from the constraint of obtaining the correct observed range of the baryon asymmetry parameter and the role played by $N_2$ is elucidated thereafter. The mildly hierarchical right-chiral neutrino case (including the quasidegenerate possibility) is discussed in an Appendix.