Prediction on Neutrino Dirac and Majorana Phases and Absolute Mass Scale from the CKM Matrix

TL;DR

This study investigates the potential connection between quark and neutrino mixing matrices within the Type-I seesaw model, predicting neutrino CP phases and mass scale consistent with experimental data.

Contribution

It demonstrates that a specific relation between the neutrino Dirac Yukawa coupling and the CKM matrix aligns with current observations, providing predictions for neutrino CP phases and mass hierarchy.

Findings

The relation $Y_D o { m diag}(y_d,y_s,y_b)V_{CKM}^T$ with normal hierarchy is consistent.

Predicted values for neutrino CP phases and lightest neutrino mass.

The relation with inverted hierarchy does not hold.

Abstract

In Type-I seesaw model, the lepton flavor mixing matrix (PMNS matrix) and the quark flavor mixing matrix (CKM matrix) may be connected implicitly through a relation between the neutrino Dirac Yukawa coupling $Y_D$ and the quark Yukawa couplings. In this paper, we study whether $Y_D$ can satisfy, in the flavor basis where the charged lepton Yukawa and right-handed neutrino Majorana mass matrices are diagonal, the relation $Y_D \propto {\rm diag}(y_d,y_s,y_b)V_{CKM}^T$ or $Y_D \propto {\rm diag}(y_u,y_c,y_t)V_{CKM}^*$ without contradicting the current experimental data on quarks and neutrino oscillations. We search for sets of values of the neutrino Dirac CP phase $\delta_{CP}$, Majorana phases $\alpha_2,\alpha_3$, and the lightest active neutrino mass that satisfy either of the above relations, with the normal or inverted hierarchy of neutrino mass. In performing the search, we consider renormalization group evolutions of the quark masses and CKM matrix and the propagation of their experimental errors along the evolutions. We find that only the former relation $Y_D \propto {\rm diag}(y_d,y_s,y_b)V_{CKM}^T$ with the normal neutrino mass hierarchy holds, based on which we make a prediction for $\delta_{CP},\,\alpha_2,\,\alpha_3$ and the lightest active neutrino mass.