Abstract
We propose a model-independent framework to classify and study neutrino mass models and their phenomenology. The idea is to introduce one particle beyond the Standard Model which couples to leptons and carries lepton number together with an operator which violates lepton number by two units and contains this particle. This allows to study processes which do not violate lepton number, while still working with an effective field theory. The contribution to neutrino masses translates to a robust upper bound on the mass of the new particle. We compare it to the stronger but less robust upper bound from Higgs naturalness and discuss several lower bounds. Our framework allows to classify neutrino mass models in just 20 categories, further reduced to 14 once nucleon decay limits are taken into account, and possibly to 9 if also Higgs naturalness considerations and direct searches are considered.
Highlights
Neutrino oscillation experiments established the need for massive neutrinos and large mixings in the lepton sector
We have derived general robust upper bounds on the mass of new particles contributing to neutrino masses
Limits from nucleon decays imply that S1, S3, S1, R2, V2 and V2 can not be the dominant source for neutrino masses, unless baryon-number conservation is imposed
Summary
Neutrino oscillation experiments established the need for massive neutrinos and large mixings in the lepton sector. We propose a hybrid approach in order to use the best of both schemes It is based on the following premises: 1. In any model of Majorana neutrino masses there is at least one new particle of mass M which directly couples to leptons and carries lepton number (and in some cases baryon number B). We assume that this is the lightest beyond the Standard Model (SM) particle involved in the generation of neutrino masses. In contrast to approaches based on effective operators alone, the introduction of the new particle enables to study processes which do not violate lepton number and their constraints on neutrino mass generation without going to explicit models. A more detailed discussion of the latter is left for future work
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
