Radiative type-I seesaw neutrino masses

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, at the one- and two-loop level, which we use to discuss neutrino masses and
lepton-flavor-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.