  The Standard Model of particle physics fails to explain the important pieces
in the standard cosmology, such as inflation, baryogenesis, and dark matter of
the Universe. We consider the possibility that the sector to generate small
neutrino masses is responsible for all of them; the inflation is driven by the
Higgs field to break $B-L$ gauge symmetry which provides the Majorana masses to
the right-handed neutrinos, and the reheating process by the decay of the $B-L$
Higgs boson supplies the second lightest right-handed neutrinos whose CP
violating decays produce $B-L$ asymmetry, a la, leptogenesis. The lightest
right-handed neutrinos are also produced by the reheating process, and remain
today as the dark matter of the Universe. In the minimal model of the inflaton
potential, one can set the parameter of the potential by the data from CMB
observations including the BICEP2 and the Planck experiments. In such a
scenario, the mass of the dark matter particle is predicted to be of the order
of PeV. We find that the decay of the PeV right-handed neutrinos can explain
the high-energy neutrino flux observed at the IceCube experiments if the
lifetime is of the order of $10^{28}$ s.
