PeV scale right-handed neutrino dark matter in an $S_4$ flavor-symmetric extra U(1) model

Recent observations of high-energy neutrinos in the IceCube experiment suggests the existence of superheavy dark matter beyond the PeV scale. We identify the parent particles of neutrinos as two degenerated right-handed neutrinos, assuming the dark matter is the heaviest right-handed neutrino. The $O(V_{cb})\sim O({10}^{-2})$ flavor symmetry breaking accounts for the $O({10}^{-4})$ mass degeneracy of right-handed neutrinos, which is a sizable scale to explain the successful resonant leptogenesis at the PeV scale. At the same time, nonthermal production of the heaviest right-handed neutrino gives the right amount of dark matter for $T_{\mathrm{RH}}\sim 10\mathrm{PeV}$. The footprint of flavor symmetry is left in the degenerated mass spectra of the extra Higgs multiplet and colored Higgs multiplet, which may be testable at the LHC or future colliders.