{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"a9932136bbb091b48cbf799713f60c4df3cd2cb64221d0afd910ab031b6693f2","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b","f149efadf15a91ad6b3b2192a848c16a13bf4958d536c71b1c88543c694986db"],"salt":"56769af83055561d51fd62a76ec74ae26a0f712a27afae4e5f0e951c3a7893b2","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":"2","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":"f149efadf15a91ad6b3b2192a848c16a13bf4958d536c71b1c88543c694986db","references":"","settled_by":"Joint IceCube-KM3NeT analysis with added exposure, and detection or exclusion of further events above $10^{17}\\,\\mathrm{eV}$.","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":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"9c0e2015c7115a7d9d7e994e6b2114a8a829ef05cf8701de6fa1a070f2435da9","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"bb0b48ecf520c7336d6b900ef8b030b89a87727bd651f37f4d3efa3cf68120f9","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"NcGeg8xz9AJaJ5__VTEDAkWdciHOtW4sQC51SgH5Nu-XSyPbH1VhwUX4QDO5UclEq04gfiif4nzX1-JeEvh3CQ"},"schema":"pubphys.envelope/1"},"record_hash":"9c0e2015c7115a7d9d7e994e6b2114a8a829ef05cf8701de6fa1a070f2435da9","leaf_index":2374}