Superheavy supersymmetric dark matter as the origin of the KM3NeT ultrahigh energy signal

We propose an explanation for the recently reported ultrahigh-energy neutrino signal at KM3NeT, which shows no clear association with known astrophysical sources. While decaying dark matter in the Galactic Center is a natural candidate, the observed arrival direction strongly suggests an extragalactic origin. We introduce a multicomponent dark matter scenario in which the components are part of a supermultiplet, with supersymmetry ensuring a nearly degenerate mass spectrum among the fields with different spins. In this setup, a cosmologically long-lived fermionic state decays into a slightly lighter bosonic dark matter state, producing a boosted neutrino spectrum with energy E ν ∼ 100 PeV , determined by the mass difference. The heavy-to-light decay occurs at a cosmological redshift of z ∼ a few or higher, leading to an isotropic directional distribution of the signal.