Entropy production from decay of GeV scale right-handed neutrinos and the primordial gravitational wave

Abstract

Right-handed neutrinos are attractive particles beyond the standard model introduced in the seesaw mechanism [1] that can explain tiny neutrino masses. We revisit the entropy production from the decay of right-handed neutrinos with GeV scale masses. This additional entropy production dilutes the dark matter and baryon abundances. Furthermore, we point out that it gives the effect on the primordial gravitational wave spectrum. Primordial gravitational waves are closely related to the thermal history of the universe, and then the modified history by right-handed neutrino is imprinted in the gravitational wave spectrum12.