Antoine Kouchner: Searches for neutrinos in the Deep-Mediterranean Sea

Tuesday 9 Sept 2025, 13:15 → 14:00 Europe/Stockholm

FB51 (AlbaNova Main Building)

Neutrinos, owing to their neutral charge and tiny interaction cross-section, traverse the Universe largely unperturbed, carrying invaluable information from the most extreme astrophysical environments. Detecting these elusive messengers requires massive instruments capable of capturing the faint Cherenkov light generated when neutrinos interact with matter. Following more than a decade of successful operation, the ANTARES detector has now been decommissioned, paving the way for the new-generation observatory KM3NeT, currently under construction at two deep-sea sites in the Mediterranean Sea. At the Toulon site (France), the KM3NeT/ORCA array is optimized for precision studies of atmospheric neutrinos, with the goal of constraining oscillation parameters and probing fundamental properties of neutrino physics. Off the coast of Sicily, the KM3NeT/ARCA array is designed to open the high-energy window of neutrino astronomy by searching for cosmic neutrino sources.

In this contribution, I will recall the key milestones that enabled the emergence of deep-sea neutrino astronomy and present recent results from ANTARES and KM3NeT. Special emphasis will be placed on the observation of a remarkable ultra-high-energy event, labeled KM3-230213A, detected by KM3NeT/ARCA. The reconstructed muon carries an energy of about 120+110−60 PeV, turning it into the most energetic neutrino-induced events ever recorded. Its extreme energy and near-horizontal direction suggest an origin in a powerful cosmic accelerator, or possibly make it a first candidate for a cosmogenic neutrino arising from interactions of ultra-high-energy cosmic rays with the diffuse photon backgrounds of the Universe. This detection illustrates the transformative potential of deep-sea neutrino telescopes in advancing both particle physics and high-energy astrophysics.