  Extending the Standard Model with right-handed neutrinos provides a minimal
explanation for both light neutrino masses (through the type-I seesaw
mechanism) and the baryon asymmetry of our universe (through leptogenesis). We
map here for the first time the range of heavy neutrino mixing angle consistent
with both neutrino masses and leptogenesis in a scenario with 3 generations of
right-handed neutrinos with Majorana masses between 50 MeV and 70 TeV. Due to
the presence of a third degree of freedom that remains much more feebly coupled
to the Standard Model thermal bath, we observe that the parameter space is much
larger compared to the minimal scenario with 2 generations. This greatly
enhances the testability prospects for low-scale leptogenesis and, in the most
optimistic scenario, would allow experimentalists not only to discover
right-handed neutrinos but also to perform consistency checks of the model.
