We study the mechanism of generation of 7 keV sterile neutrino Dark Matter ( DM ) in the model with light inflaton \chi , which serves as a messenger of scale invariance breaking .
In this model the inflaton , in addition to providing reheating to the Standard Model ( SM ) particles , decays directly into sterile neutrinos .
The latter are responsible for the active neutrino oscillations via seesaw type I mechanism .
While the two sterile neutrinos may also produce the lepton asymmetry in the primordial plasma and hence explain the baryon asymmetry of the Universe , the third one being the lightest may be of 7 keV and serve as DM .
For this mechanism to work , the mass of the inflaton is bound to be light ( 0.1 - 1 GeV ) and uniquely determines its properties , which allows to test the model .
For particle physics experiments these are : inflaton lifetime ( 10 ^ { -5 } -10 ^ { -12 } s ) , branching ratio of B-meson to kaon and inflaton ( 10 ^ { -6 } -10 ^ { -4 } ) and inflaton branching ratios into light SM particles like it would be for the SM Higgs boson of the same mass .
For cosmological experiments these are : spectral index of scalar perturbations ( n _ { s } \simeq 0.957 - 0.967 ) , and amount of tensor perturbations produced at inflation ( tensor-to-salar ratio r \simeq 0.15 - 0.005 ) .