Minimal Realizations of Dirac Neutrino Mass from Generic One-loop and Two-loop Topologies at $d=5$

TL;DR

This paper systematically identifies minimal one-loop and two-loop models for Dirac neutrino masses arising from a $d=5$ operator, within a $U(1)_{B-L}$ framework, highlighting many new viable models and potential dark matter candidates.

Contribution

It provides a comprehensive classification of minimal Dirac neutrino mass models from generic loop topologies at $d=5$, including new models with colored particles and dark matter considerations.

Findings

Seventeen minimal one-loop Dirac neutrino models identified.

Twenty-three minimal two-loop Dirac neutrino models constructed.

Most proposed models are novel contributions to the field.

Abstract

We carry out a systematic investigation for the minimal Dirac neutrino mass models emerging from generic one-loop and two-loop topologies that arise from $d=5$ effective operator with a singlet scalar, $\sigma$. To ensure that the tree-level Dirac mass, as well as Majorana mass terms at all orders, are absent for the neutrinos, we work in the framework where the Standard Model is supplemented by the well-motivated $U(1)_{B-L}$ gauge symmetry. At the one-loop level, we analyze six possible topologies, out of which two of them have the potential to generate desired Dirac neutrino mass. Adopting a systematic approach to select minimal models, we construct seventeen viable one-loop Dirac neutrino mass models. By embracing a similar methodical approach at the two-loop, we work out twenty-three minimal candidates. Among the forty selected economical models, the majority of the models proposed in this work are new. In our search, we also include the scenarios where the particles in the loop carry charges under the color group. Furthermore, we discuss the possible dark matter candidates within a given model, if any, without extending the minimal particle content.