I will talk about the observation of an ultra-high-energy cosmic neutrino with KM3Net in 2023. It is reported that its energy is ~100PeV and the origin is unknown. Then, I will introduce an explanation of its origin by super heavy dark matter investigated in a recent paper.
References:
1. Nature 638 (2025) 8050, 376-382
2. arXiv: 2503.04464