Observation of the first ultra-high-energy cosmic neutrino with KM3NeT

Thursday 20 Mar 2025, 15:00 → 16:00 Europe/Rome

aula magna (Dipartimento di Fisica)

Antonio Marinelli (Istituto Nazionale di Fisica Nucleare)

Abstract: In this presentation we report an exceptional observation made by the KM3NeT telescope on 13th February 2023, when a horizontal track produced by a 120 petaelectronvolts (PeV) muon was recorded. The neutrino associated to the observed muon has an estimated energy of  220 (72 PeV – 2.6 EeV) petaelectronvolts (PeV), the most energetic neutrino so far recorded. Such events can be produced when ultra-relativistic cosmic-ray protons or nuclei, emitted in the extreme astrophysical conditions, interact with matter or photons. While the cosmic neutrino energy spectrum measured up to date falls steeply with energy, the flux inferred by this event breaks the TeV-PeV known power laws with a suddenly hardening above that energies. This suggests that the neutrino may have originated in a different cosmic environment than the lower-energy neutrinos, or this may be the first detection of a cosmogenic neutrino, resulting from the interactions of ultra-high-energy cosmic rays with background photons in the Universe. Based on this assumption this event can be a signature of the furthest cosmic accelerator so far observed in this energy range. Different scenarios made to explain it will be treated in this talk.