IceCube Events from Heavy DM decays through the Right-handed Neutrino Portal

The recently observed IceCube PeV events could be due to heavy dark matter (DM) decay. In this paper, we propose a simple DM model with extra $U(1)_X$ gauge symmetry and bridge it with standard model particles through heavy right-handed neutrino. The Dirac fermion DM $\chi$ with mass ~5 PeV can dominantly decay into a dark Higgs ($\phi$), the SM Higgs ($h$) and a neutrino ($\nu$). If the lifetime of $\chi$ is ~O($10^{28}$) sec, the resulting neutrino flux can fit data consistently. The neutrino flux from $\chi \rightarrow \phi h \nu$ in our model is softer than the one predicted from $\chi \rightarrow \nu h$, for example. We also discuss a possible mechanism to produce DM with the right relic abundance.