# Loop neutrino masses from d=7 operator

## TL;DR

This paper systematically analyzes all possible one-loop topologies for generating small neutrino masses via dimension-7 operators, identifying genuine models where the dimension-7 contribution is dominant and classifying them by particle content.

## Contribution

It provides a comprehensive classification of all genuine d=7 one-loop neutrino mass models, including their particle content and minimal examples.

## Key findings

- Only 8 of 48 topologies lead to genuine d=7 neutrino masses.
- One diagram involves no representation larger than triplet, 22 involve quadruplets.
- Three minimal example models are briefly discussed.

## Abstract

We discuss the generation of small neutrino masses from d=7 1-loop diagrams. We first systematically analyze all possible d=7 1-loop topologies. There is a total of 48 topologies, but only 8 of these can lead to "genuine" d=7 neutrino masses. Here, we define genuine models to be models in which neither d=5 nor d=7 tree-level masses nor a d=5 1-loop mass appear, such that the d=7 1-loop is the leading order contribution to the neutrino masses. All genuine models can then be organized w.r.t. their particle content. We find there is only one diagram with no representation larger than triplet, while there are 22 diagrams with quadruplets. We briefly discuss three minimal example models of this kind.