Heavy right-handed neutrino dark matter and PeV neutrinos at IceCube
  We discuss a simple non-supersymmetric model based on the electroweak gauge
group $SU(2)_L\times SU(2)^\prime\times U(1)_{B-L}$ where the lightest of the
right-handed neutrinos, which are part of the leptonic doublet of
$SU(2)^\prime$, play the role of a long-lived unstable dark matter with mass in
the multi-PeV range. We use a resonant $s$-channel annihilation to obtain the
correct thermal relic density and relax the unitarity bound on dark matter
mass. In this model, there exists a 3-body dark matter decay mode producing tau
leptons and neutrinos, which could be the source for the PeV cascade events
observed in the IceCube experiment. The model can be tested with more precise
flavor information of the highest-energy neutrino events in future data.
