KM3NeT finds ultrahigh-energy neutrino

davidwr writes: Multiple (space.com) sources (nytimes, may be paywalled) announce that the Kilometer Cube Neutrino Telescope (KM3NeT) has found an "ultrahigh energy" neutrino. They are still working out where it originated from, but the main suspects are blazars. Another theory is that "an ultramassive cosmic ray particle slammed into particles of light ... left in the universe after some event that occurred just after the Big Bang."

The event itself, KM3-230213A, occurred on 13 February 2023.

Journal citation:

The KM3NeT Collaboration. Observation of an ultra-high-energy cosmic neutrino with KM3NeT. Nature 638, 376–382 (2025). https://doi.org/10.1038/s41586-024-08543-1