High Energy Neutrinos, Gravitational Waves, and Dark Matter from a Cosmological First Order Phase Transition

We investigate high energy neutrinos (HE ν s) from the decay of superheavy dark matter (DM) produced during a cosmological first order phase transition. Adopting the filtered DM production mechanism, we revisit the relic abundance calculation by incorporating recent progress in determining the bubble wall velocity from hydrodynamics. We show that DM with mass m DM 4.4 times10 8 GeV can reproduce the observed relic abundance and accommodate ultra high energy neutrino events such as KM3-230213A, while the same phase transition simultaneously generates a stochastic gravitational wave (GW) background. Although the GW signal (which peaks at 10 4, Hz) is not yet observable in this example, at lower DM masses m DM 10 6 GeV, the neutrino spectrum shifts into the energy range relevant for IceCube observations, while the associated GW signal moves to lower frequencies and can reach the projected sensitivities of Cosmic Explorer, BBO, and DECIGO. This gives a multimessenger connection between HE ν s and GWs, with both signals connected to DM production in a first order phase transition.