A minimal extension of the Standard Model is proposed, where the observed
left-handed neutrinos obtain naturally small Majorana masses from a one-loop
radiative seesaw mechanism. This model has two candidates (one bosonic and one
fermionic) for the dark matter of the Universe. It has a very simple structure
and should be verifiable in forthcoming experiments at the Large Hadron
Collider.Comment: 8 pages, 1 figur
