Neutrino masses and mixing in A4 models with three Higgs doublets

Understand

We study neutrino masses and mixing in the context of flavor models with A4 symmetry, three scalar doublets in the triplet representation, and three lepton families.

• We show that there is no representation assignment that yields a dimension-five mass operator consistent with experiment.
• We then consider a type-I seesaw with three heavy right-handed neutrinos, explaining in detail why it fails, and showing with a numerical example that agreement with the present neutrino oscillation data can be recovered with the inclusion of dimension-three heavy neutrino mass terms that break softly the A4 symmetry.