Confronting Four Zero Neutrino Yukawa Textures with $N_2^{}$-dominated Leptogenesis

TL;DR

This paper investigates a specific neutrino mass model with four texture zeros and hierarchical Yukawa couplings, showing that leptogenesis constraints limit possible textures and challenge quasi-degenerate neutrino scenarios.

Contribution

It introduces a restricted Type-I seesaw model with four texture zeros and hierarchical Yukawa matrices, analyzing its implications for leptogenesis and neutrino mass patterns.

Findings

Leptogenesis constrains the allowed textures significantly.

Hierarchical Yukawa patterns disfavor quasi-degenerate neutrinos.

Upcoming experiments may test the quasi-degenerate neutrino scenario.

Abstract

We consider a restricted Type-I seesaw scenario with four texture zeros in the neutrino Yukawa matrix, in the weak basis where both the charged-lepton Yukawa matrix and the Majorana mass matrix for right-handed neutrinos are diagonal and real. Inspired by grand unified theories, we further require the neutrino Yukawa matrix to exhibit a similar hierarchical pattern to that in the up-type quark Yukawa matrix. With such a hierarchy requirement, we find that leptogenesis, which would operate in a $N_2^{}$-dominated scenario with the asymmetry generated by the next-to-lightest right-handed neutrino $N_2^{}$, can greatly reduce the number of allowed textures, and disfavors the scenario that three light neutrinos are quasi-degenerate. Such a quasi-degenerate scenario of light neutrinos may soon be tested in upcoming neutrino experiments.