  The extension of the Standard Model with two gauge-singlet Majorana fermions
can simultaneously explain two beyond-the-Standard-model phenomena: neutrino
masses and oscillations, as well as the origin of the matter-antimatter
asymmetry in the Universe. The parameters of such a model are constrained by
the neutrino oscillation data, direct accelerator searches, big bang
nucleosynthesis, and requirement of successful baryogenesis. We show that the
combination of all these constraints still leaves an allowed region in the
parameter space below the kaon mass. This region can be probed by the further
searches of NA62, DUNE, or SHiP experiments.
