Reconciling neutrino flux from heavy dark matter decay and recent events at IceCube

The IceCube detector has recently reported the observation of 28 events at previously unexplored energies. While the statistics of the observed events are still low, these events strongly hint at the existence of a neutrino flux over and above the atmospheric neutrino background. We investigate the possibility that a significant component of the additional neutrino flux originates due to the decay of a very heavy dark matter (VHDM) particle via several possible channels into standard model particles. We show that a combination of a power law astrophysical neutrino spectrum and the neutrino flux from the decay of a DM species of mass in the range $150-400$ TeV provides a significantly better fit to the observed neutrino events than does the astrophysical flux alone. In addition, we also show that for the decay of even heavier DM particles ($m_{\text{DM}} \sim 1$ PeV), the same observations impose strict constraints on the decay lifetimes. We study several different channels by which dark matter can decay into standard model particles, to arrive at model-independent lower bounds for the decay lifetimes of VHDM.