Radiative type-I seesaw neutrino masses

TL;DR

This paper explores a radiative type-I seesaw mechanism for neutrino mass generation, showing how loop processes can explain small neutrino masses with relatively light right-handed neutrinos, and discusses testable models at collider experiments.

Contribution

It introduces a general framework for radiative type-I seesaw models, estimating right-handed neutrino mass scales and providing explicit one- and two-loop examples with phenomenological implications.

Findings

Two-loop model predicts right-handed neutrino masses below 100 GeV.

Radiative mechanisms can generate small neutrino masses with lighter right-handed neutrinos.

Models are testable via heavy neutral lepton searches.

Abstract

We discuss a radiative type-I seesaw. In these models, the radiative generation of Dirac neutrino masses allows to explain the smallness of the observed neutrino mass scale for rather light right-handed neutrino masses in a type-I seesaw. We first present the general idea in a model independent way. This allows us to estimate the typical scale of right-handed neutrino mass as a function of the number of loops. We then present two example models, one at one-loop and another one at two-loop, in which we discuss neutrino masses and lepton flavour violating constraints in more detail. For the two-loop example, right-handed neutrino masses must lie below 100 GeV, thus making this class of models testable in heavy neutral lepton searches.