On 13 February 2023, the ARCA detector of the KM3NeT underwater neutrino telescope detected an extraordinary event associated with a neutrino of an estimated energy much greater than the particles produced by the LHC at CERN: about 220 PeV (220,000 billion electronvolts). This event, called KM3-230213A, is the most energetic neutrino ever observed to date and provides the first evidence that neutrinos of these characteristics are produced in the Universe. After a long and painstaking work to analyse and interpret the data, the KM3NeT collaboration has just reported on the details of this finding in an article published in Nature.
The detected event was identified as a muon -an elementary particle related to the electron- that passed through the detector, producing signals in more than one third of the sensors. The inclination of its trajectory, together with its enormous energy, provides convincing evidence that the muon originated from a cosmic neutrino interacting in the vicinity of the detector.
"KM3NeT has begun exploring a range of energy and sensitivity where the detected neutrinos can be produced in extreme astrophysical phenomena. This first detection of a hundreds of PeV neutrino opens a new chapter in neutrino astronomy and a new window into the observation of the universe", says Paschal Coyle, KM3NeT spokesperson at the time of detection and researcher at the IN2P3/CNRS Centre for Particle Physics in Marseille (France).
"Neutrinos are very mysterious elementary particles. They have no electric charge, little mass and interact weakly with matter. They are special cosmic messengers, who provide us with unique information about the mechanisms involved in the most energetic phenomena and allow us to explore the far reaches of the universe." Rosa Coniglione, deputy spokesperson for KM3NeT at the time of detection and researcher at the Italian National Institute of Nuclear Physics (INFN)
Access the reel on the channel of the Science Park at the University of Valencia where IFIC staff explain the AION project.
Neutrinos, the most mysterious elementary particles
The high-energy universe is the realm of colossal events such as supermassive black holes, supernova explosions and gamma-ray bursts, events that are not yet fully understood. These powerful cosmic accelerators generate streams of particles called cosmic rays, which can interact with the matter around them to produce neutrinos and photons. During their journey through the universe, the most energetic cosmic rays can interact with the photons of microwave background radiation, the first light after the origin of the cosmos, to produce extremely energetic neutrinos, called cosmogenic.
"Neutrinos are very mysterious elementary particles. They have no electric charge, little mass and interact weakly with matter. They are special cosmic messengers, providing us with unique information about the mechanisms involved in the most energetic phenomena and allowing us to explore the far reaches of the universe," explains Rosa Coniglione, Deputy Spokesperson for KM3NeT at the time of detection and researcher at the Italian National Institute of Nuclear Physics (INFN).
Future observations will focus on detecting more such events to build a clearer picture. The ongoing expansion of KM3NeT with additional detection units and the acquisition of new data will improve its sensitivity and increase its ability to identify sources of cosmic neutrinos, making KM3NeT a major player in multi-messenger astronomy
Although it is the second most abundant particle in the universe, after photons forming light, the extremely weak interaction of neutrinos with matter makes them very difficult to identify, so huge detectors are required. The KM3NeT telescope, currently under construction, is a gigantic infrastructure at the bottom of the sea containing two detectors - ARCA and ORCA- that uses seawater as an interaction medium to detect neutrinos. Its high-tech optical modules capture the Cherenkov light, a bluish glow that generates the propagation in water of ultra-relativistic particles resulting from neutrino interactions.
This ultra-high energy neutrino may have originated directly from a powerful cosmic accelerator. Alternatively, it could be the first detection of a cosmogenic neutrino, although it is difficult to reach conclusions about its origin, according to the scientists at the collaboration. Future observations will focus on detecting more such events to build a clearer picture. The ongoing expansion of KM3NeT with additional detection units and the acquisition of new data will improve its sensitivity and increase its ability to identify sources of cosmic neutrinos, making KM3NeT a major player in multi-messenger astronomy.
The IFIC group called VEGA (Valencia Experimental Group of Astroparticles) is made up of about twenty members, men and women also from science and engineering. "Some of the key elements of the detector, such as the main acquisition electronic cards and some elements for calibration have been designed and tested in our laboratory
Spanish participation in KM3NeT
The KM3NeT collaboration brings together more than 360 scientists, engineers, technical staff and students from 68 institutions in 22 countries. In Spain, the Institute of Corpuscular Physics (IFIC), the Polytechnic University of Valencia (UPV), the University of Granada, the Joint Unit of the Spanish Institute of Oceanography (IEO, CSIC) and the LAB of the Polytechnic University of Catalonia are involved.
Coordinated by the physicist of the University of Valencia at IFIC Juan de Dios Zornoza Gómez, the participation of Spanish groups in KM3NeT is financed by various programmes of the Ministry of Science, Innovation and Universities, as well as European and regional programmes (Generalitat Valenciana and Junta de Andalucía).
The IFIC group called VEGA (Valencia Experimental Group of Astroparticles) is made up of about twenty members, men and women also from science and engineering. "Some of the key elements of the detector, such as the main acquisition electronic cards and some elements for calibration, have been designed and tested in our laboratory. In addition, we have participated and even led several analyses on multi-messenger astronomy, neutrino oscillations or search for dark matter and new physics through neutrinos, among others. The plan is to continue working on all these fronts", explains Juan de Dios Zornoza. "We are working to get a deeper knowledge of this extraordinary event and hope to continue to reap new results according to the large volume of opportunities that neutrino astronomy offers," concludes Juan José Hernández Rey, CSIC research professor and founder of the VEGA group at IFIC.
Neutrino astronomy
The field of neutrino astronomy is in full expansion, and the Spanish research teams are confident that once the installation of the two KM3NeT detectors is complete, new data will be obtained on the mystery of the origin of cosmic neutrinos. "Precise telescope calibration and sophisticated trace reconstruction algorithms were required to determine the direction and energy of this neutrino. In addition, the finding occurred with only one tenth of the final detector configuration, demonstrating the great potential of our experiment for neutrino study and neutrino astronomy," adds Aart Heijboer, Physics and Software coordinator of KM3NeT at the time of detection and researcher at the National Institute for Subatomic Physics (Nikhef), in the Netherlands.
Source: UV News, CSIC