IceCube events and decaying dark matter: hints and constraints
  In the light of the new IceCube data on the (yet unidentified) astrophysical
neutrino flux in the PeV and sub-PeV range, we present an update on the status
of decaying dark matter interpretation of the events. In particular, we develop
further the angular distribution analysis and discuss the perspectives for
diagnostics. By performing various statistical tests (maximum likelihood,
Kolmogorov-Smirnov and Anderson-Darling tests) we conclude that currently the
data show a mild preference (below the two sigma level) for the angular
distribution expected from dark matter decay vs. the isotropic distribution
foreseen for a conventional astrophysical flux of extragalactic origin. Also,
we briefly develop some general considerations on heavy dark matter model
building and on the compatibility of the expected energy spectrum of decay
products with the IceCube data, as well as with existing bounds from
gamma-rays. Alternatively, assuming that the IceCube data originate from
conventional astrophysical sources, we derive bounds on both decaying and
annihilating dark matter for various final states. The lower limits on heavy
dark matter lifetime improve by up to an order of magnitude with respect to
existing constraints, definitively making these events---even if astrophysical
in origin---an important tool for astroparticle physics studies.
