Discovery of an ultra-high-energy particle (neutrino)
irmp | Louvain-la-Neuve
Every second, trillions of neutrinos pass through each of us. These extremely abundant particles give astrophysicists a new lens to better understand our cosmos. Despite their abundance in the universe, neutrinos interact very little with matter, making these “ghost particles” extremely difficult to detect. These cosmic messengers, with a mass a million times smaller than that of an electron, travel in straight lines, emitted during cosmic events. By studying their origin, high-energy astrophysical neutrinos could provide unique clues about cataclysmic events such as star explosions or black holes.
A detection module of the KM3NeT telescope during an operation at sea. It is one of the thousands of eyes of the instrument to capture neutrinos. Credits: Paschal Coyle, CNRS.
To detect these elusive particles and decipher all they can reveal, UCLouvain professor Gwenhaël Wilberts Dewasseige and her team work with two cubic-kilometer telescopes buried under the Antarctic ice (IceCube) and in the Mediterranean Sea (KM3NeT). Using KM3NeT, UCLouvain scientists, in collaboration with an international research team, discovered a neutrino with an unprecedented estimated energy of about 220 petaelectronvolts (PeV)—thirty times higher than any neutrino previously detected worldwide.
Visual representation of the neutrino observed by KM3NeT. The colored lines indicate the light captured by the different “eyes” of the instrument, with the various colors representing the time of observation (from violet to cyan). The white line is the reconstructed trajectory crossing the detector from right to left. Credits: KM3NeT.
This groundbreaking discovery represents a significant step forward in understanding the extreme energetic phenomena of the Universe. This invaluable discovery has been published on the cover of the prestigious scientific journal Nature.
The result is the culmination of months of simulations, calibrations, and rigorous signal verification. KM3NeT is a giant observatory composed of thousands of light sensors. Its detectors are located at two deep-sea sites in the Mediterranean: ARCA, dedicated to high-energy astronomy off the coast of Sicily, Italy, and ORCA, specializing in low-energy studies near Toulon, France. Scientists benefit from the deep sea’s transparency, darkness, and minimal atmospheric background noise—ideal conditions to observe Cherenkov light, a phenomenon associated with neutrino detection. The regular addition of new detection lines will allow the telescope to become fully operational by 2030, enabling even more advanced results in the study of neutrinos and the mysteries of the Universe.
Photo of a KM3NeT detection line, made up of a bundle of eighteen modules, ready to be deployed with its anchor (in yellow). Credits: Andrea Simonelli, INFN.
This research project involved a team of five scientists alongside Professor Gwenhaël Wilberts Dewasseige within the neutrino astrophysics group at UCLouvain: Eliot Genton (FNRS Aspirant), Mathieu Lamoureux (FNRS Research Associate), Jeffrey Lazar (FNRS Research Associate), Jonathan Mauro (FRIA Doctoral Researcher), and Per Arne Sevle Myhr (BELSPO Doctoral Researcher).
For the young doctoral researchers, this experience was particularly enriching. “It's been exciting to see such an important discovery early in my research career. The whole collaboration came together to share the results with the community as quickly as possible, and it was great to be an active part of the process” says Jonathan Mauro.
But this scientific breakthrough also prompted the more experienced researchers to reflect on the future direction of neutrino astrophysics research. “Participating in research conducted with both telescopes (Antarctic and Mediterranean) allows us to leverage the unique complementarities of these sites,” explains Mathieu Lamoureux. “In the coming years, this approach will be essential for deepening our understanding of the origins of astrophysical neutrinos and the phenomena occurring within the most extreme objects in our Universe.”
Article written by Eliot Genton and Jeff Lazar.