Original title: IceCube neutrino point-source searches in the direction of the KM3NeT ultra-high-energy event
R. Abbasi, M. Ackermann, J. Adams, J. A. Aguilar +415 · September 2026
On February 13th, 2023, an underwater detector called KM3NeT recorded a neutrino with an energy of ~200 PeV. Neutrinos are tiny subatomic particles from space, and this is the highest-energy neutrino reported. Scientists wanted to confirm where it came from. So, researchers turned to IceCube, a giant cubic kilometer detector at the South Pole that has observed neutrinos up to approximately 10 PeV. They checked 15 years of IceCube data, looking at the exact spot in the sky where the huge particle originated. They tested whether that source emitted neutrinos steadily or in quick bursts. IceCube found no extra neutrinos from that location. This missing signal puts tight limits on whether standard cosmic sources produced the event.
Imagine you hear a single loud bang in a quiet forest. You listen for another bang from the same direction for the next hour, but hear nothing. That single bang could be a one-off tree falling, not a steady firework show. In this paper, the bang is the 200 PeV neutrino detected by KM3NeT, and IceCube listened for more neutrinos from that spot for 15 years but found none, suggesting the event was likely a rare, transient explosion rather than a persistent source.
Astronomers hope ultra-high-energy neutrinos reveal the most violent places in the universe. But when KM3NeT spotted one at 200 PeV—the highest ever—IceCube found nothing else from that spot over 15 years. This means the source is either extremely faint, incredibly rare, or both, making it much harder to track down.
This search only tests point-source models from a single direction; it does not rule out extended sources or a diffuse background. The upper limits depend on the assumed spectral index, with the strongest constraints for an index of 2.0. Other spectral shapes may be less constrained. The analysis cannot exclude a one-time transient that produced only the single detected neutrino.
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IceCube neutrino point-source searches in the direction of the KM3NeT ultra-high-energy event — R. Abbasi, M. Ackermann, J. Adams et al.
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.