Probing Models of Dirac Neutrino Masses via the Flavor Structure of the Mass Matrix

TL;DR

This paper classifies Dirac neutrino mass models based on flavor structures of the mass matrix, providing a framework to test these models through neutrino mass measurements, lepton universality tests, and collider searches.

Contribution

It introduces a model-independent classification of Dirac neutrino mass models based on Yukawa matrix products, facilitating experimental testing of different flavor structure groups.

Findings

Seven distinct flavor structure groups identified

Some groups testable via absolute neutrino mass measurements

Others accessible through collider searches and lepton universality tests

Abstract

We classify models of the Dirac neutrino mass by concentrating on flavor structures of the mass matrix. The advantage of our classification is that we do not need to specify detail of models except for Yukawa interactions because flavor structures can be given only by products of Yukawa matrices. All possible Yukawa interactions between leptons (including the right-handed neutrino) are taken into account by introducing appropriate scalar fields. We also take into account the case with Yukawa interactions of leptons with the dark matter candidate. Then, we see that flavor structures can be classified into seven groups. The result is useful for the efficient test of models of the neutrino mass. One of seven groups can be tested by measuring the absolute neutrino mass. Other two can be tested by probing the violation of the lepton universality in $\ell \to \ell^\prime \nu \overline{\nu}$. In order to test the other four groups, we can rely on searches for new scalar particles at collider experiments.