{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"8f7792b3010544b07076a9ea7d10202fc5908ccbecae4c222f2e46696ab51bf3","created":"2026-10-03T07:17:55Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"84e23c7edf14c2e4ffe7453d787f06db144f357411432a8a7a73debcb4db796b","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"astro.high-energy-neutrino-sources.km3-event","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"In 2023 a detector in the Mediterranean recorded a neutrino about 30 times more energetic than any seen before, while the larger IceCube detector has seen none like it.","posed_since":"2025","precise":"KM3-230213A (reconstructed neutrino energy $\\sim 220\\,\\mathrm{PeV}$, 72 PeV to 2.6 EeV at 90 percent confidence) implies, if steady and isotropic, a flux in tension at about 2.5 to 3 $\\sigma$ with IceCube non-detections above 10 PeV. Determine whether it is a cosmogenic neutrino, emission from a transient point source such as a flaring blazar in the error region, or an upward fluctuation, and which flux is consistent with both detectors. Answer: a joint flux estimate and a source attribution with probabilities.","problem_ref":null,"references":"","settled_by":"Joint IceCube-KM3NeT analysis with added exposure, and detection or exclusion of further events above $1e17\\,\\mathrm{eV}$.","status_note":"2025: KM3NeT published the event; follow-up analyses found that a steady cosmogenic origin requires a flux in tension with IceCube limits, leaving transient and fluctuation explanations.","title":"Origin of the $220\\,\\mathrm{PeV}$ neutrino event KM3-230213A","topic_ref":"05faf7b2786da464712d8108b8ce0e3e18f89534b1760bb4d3030768e35f2a73"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"f149efadf15a91ad6b3b2192a848c16a13bf4958d536c71b1c88543c694986db","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"4023169db35214e901f8f4aba19884cd5bc882a340def6faf1f24af79ac97277","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"T0co5MB_kxhgxiH_e5gWLp37G15D-SKB_5LVwOhIsGnMQg8rLvlCOVnM3zG31xXcl2V_IeCYGlzV1IbqGN-FDA"},"schema":"pubphys.envelope/1"},"record_hash":"f149efadf15a91ad6b3b2192a848c16a13bf4958d536c71b1c88543c694986db","leaf_index":553}