ARCA

2 Articles

One of the photo-detector spheres of ARCA (Credit: KM3NeT)

Confirmation Of Record 220 PeV Cosmic Neutrino Hit On Earth

August 26, 2025 by 4 Comments

Neutrinos are exceedingly common in the Universe, with billions of them zipping around us throughout the day from a variety of sources. Due to their extremely low mass and no electric charge they barely ever interact with other particles, making these so-called ‘ghost particles’ very hard to detect. That said, when they do interact the result is rather spectacular as they impart significant kinetic energy. The resulting flash of energy is used by neutrino detectors, with most neutrinos generally pegging out at around 10 petaelectronvolt (PeV), except for a 2023 event.

This neutrino event which occurred on February 13th back in 2023 was detected by the KM3NeT/ARCA detector and has now been classified as an ultra-high energy neutrino event at 220 PeV, suggesting that it was likely a cosmogenic neutrinos. When we originally reported on this KM3-230213A event, the data was still being analyzed based on a detected muon from the neutrino interaction even, with the researchers also having to exclude the possibility of it being a sensor glitch.

By comparing the KM3-230213A event data with data from other events at other detectors, it was possible to deduce that the most likely explanation was one of these ultra-high energy neutrinos. Since these are relatively rare compared to neutrinos that originate within or near Earth’s solar system, it’ll likely take a while for more of these detection events. As the KM3NeT/ARCA detector grid is still being expanded, we may see many more of them in Earth’s oceans. After all, if a neutrino hits a particle but there’s no sensor around to detect it, we’d never know it happened.

Top image: One of the photo-detector spheres of ARCA (Credit: KM3NeT)

One of the photo-detector spheres of ARCA (Credit: KM3NeT)

Most Energetic Cosmic Neutrino Ever Observed By KM3NeT Deep Sea Telescope

February 14, 2025 by 7 Comments

On February 13th of 2023, ARCA of the kilometre cubic neutrino telescope (KM3NeT) detected a neutrino with an estimated energy of about 220 PeV. This event, called KM3-230213A, is the most energetic neutrino ever observed. Although extremely abundant in the universe, neutrinos only weakly interact with matter and thus capturing such an event requires very large detectors. Details on this event were published in Nature.

Much like other types of telescopes, KM3NeT uses neutrinos to infer information about remote objects and events in the Universe, ranging from our Sun to other solar systems and galaxies. Due to the weak interaction of neutrinos they cannot be observed like photons, but only indirectly via e.g. photomultipliers that detect the blue-ish light of Cherenkov radiation when the neutrino interacts with a dense medium, such as the deep sea water in the case of ARCA (Astroparticle Research with Cosmics in the Abyss). This particular detector is located at a depth of 3,450 meters off the coast of Sicily with 700 meter tall detection units (DUs) placed 100 meters apart which consist out of many individual spheres filled with detectors and supporting equipment.

With just one of these high-power neutrinos detected it’s hard to say exactly where or what it originated from, but with each additional capture we’ll get a clearer picture. For a fairly new neutrino telescope project it’s also a promising start especially since the project as a whole is still under construction, with additional detectors being installed off the coasts of France and Greece.