Confronting four zero neutrino Yukawa textures with $N_2$-dominated leptogenesis

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 hierarchical pattern similar to that in the up-type quark Yukawa matrix. With such a hierarchy requirement, we find that leptogenesis, which would operate in an $N_2$-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 that it disfavors the scenario that three light neutrinos are quasidegenerate. Such a quasidegenerate scenario of light neutrinos may soon be tested in upcoming neutrino experiments.

Figure 1

Allowed parameter space for $m_{1,3}$, $\delta$, and $M_{ee}$ in class IA (red), class IB (green), class IIA (blue), and class IIB (black). The left and right panels give the parameter space in terms of ($m_{1,3}$ vs $\delta$) and ($m_{1,3}$ vs $M_{ee}$), respectively, while the top (NH) and bottom (IH) panels are distinguished by two different mass hierarchies of neutrinos. Note that the orange dashed contours on the right panels indicate the allowed regions for ($m_{1,3}$ vs $M_{ee}$), given the current $3\sigma$ data from neutrino oscillation experiments.

Figure 2

Allowed parameter space for $m_1$, $\delta$, and $M_{ee}$ in class IB with NH. The orange dashed contour labeled by “LE” is the same $3\sigma$ contour given in Fig. 1.

Figure 3

Allowed parameter space for $m_1$, $\delta$, and $M_{ee}$ in classes IIA and IIB with NH.

Figure 4

Allowed parameter space for $m_3$, $\delta$, and $M_{ee}$ in classes IB and IIB with IH.

Figure 5

Allowed parameter space for $m_3$, $\delta$, and $M_{ee}$ in class IB with IH. Note that there exists another branch of parameter space in the top panel with $\delta \to \delta +180°$.