Parallel seesaw mechanisms for neutrinos and freeze-in long-lived dark matter

If dark matter is light, it may be due to a seesaw mechanism just as neutrinos are. It is postulated that both originate from the same type of heavy fermion anchors, either singlets or triplets. In the latter case, a shift of the W mass is predicted, as suggested by the C D F precision measurement. A spontaneously broken dark U (1) gauge symmetry is assumed, resulting in freeze-in long-lived light dark matter.