Extending two Higgs doublet models for two-loop neutrino mass generation and one-loop neutrinoless double beta decay

TL;DR

This paper proposes an extension to two Higgs doublet models by adding charged singlet scalars, enabling two-loop neutrino mass generation and one-loop neutrinoless double beta decay, with testable experimental predictions.

Contribution

It introduces a novel scalar extension to two Higgs doublet models that fully determines the neutrino mass matrix and predicts observable neutrinoless double beta decay at one-loop level.

Findings

Neutrino masses generated via two-loop diagrams involving new scalars.

Neutrinoless double beta decay can occur at one-loop level with testable signals.

Model constraints from rare processes and Higgs phenomenology are analyzed.

Abstract

We extend some two Higgs doublet models, where the Yukawa couplings for the charged fermion mass generation only involve one Higgs doublet, by two singlet scalars respectively carrying a singly electric charge and a doubly electric charge. The doublet and singlet scalars together can mediate a two-loop diagram to generate a tiny Majorana mass matrix of the standard model neutrinos. Remarkably, the structure of the neutrino mass matrix is fully determined by the symmetric Yukawa couplings of the doubly charged scalar to the right-handed leptons. Meanwhile, a one-loop induced neutrinoless double beta decay can arrive at a testable level even if the electron neutrino has an extremely small Majorana mass. We also study other experimental constraints and implications including some rare processes and Higgs phenomenology.