Neutrino masses beyond the minimal seesaw

TL;DR

This paper reviews various mechanisms beyond the minimal seesaw for generating small neutrino masses, including higher-dimensional operators and radiative models, with a focus on classifying and understanding genuine loop diagrams.

Contribution

It provides a systematic classification of higher-dimensional and radiative neutrino mass models, highlighting special genuine loop diagrams with specific conditions.

Findings

Classification of higher-dimensional neutrino mass models

Identification of genuine loop diagrams and their conditions

Insights into alternative neutrino mass generation mechanisms

Abstract

The simplest possibility to generate small Majorana neutrino masses is the seesaw mechanism. However, the smallness of the observed neutrino masses can also be understood, if neutrino masses are generated by higher-dimensional operators and/or at higher loop level. In this talk recent work on systematic classifications of higher-dimensional and radiative neutrino mass models is summarized. Two particular classes of special genuine loop diagrams, i.e. diagrams which can lead to genuine neutrino mass models only under some specific, well-defined conditions, are also discussed.