MAJORANA DARK MATTER

摘要

In this letter in the framework of a simple see-saw scenario with three quasidegenerate Majorana neutrinos we propose~* that one of these neutrinos canbe very weakly coupled, yet there is a mechanism of the generation of theabundance of such "dark" neutrino in the early universe. The mechanism ofproduction is due to oscillations between "dark" Majorana neutrino and oneof the Majorana's which has relatively large Yukawa couplings ("bright" Ma-jorana neutrino). The transition of "bright" Majorana into a "dark" one isnonadiabatic. We point out on the similarity with the Landau-Zener transitionregime. In our model one can explain the observed dark matter density, presentmatter-antimatter asymmetry and active neutrino data all at the same time.