Neutrinos are almost Masselos and hardly interact with matter – they are correspondingly difficult to detect. Now physicists have captured the trail of one of these elementary particles that was more energy -sided as ever. The cosmic neutrino had an energy of 220 petaelectron volt-this corresponds to the 22-brilliant times the energy of an electron. The extremely energy-rich cosmic neutrino was detected by the neutrino observatory kilometr cube neutrino telescope (km3net) only under construction at the bottom of the Mediterranean. This caught the weak glow that created the interaction of neutrino with matter and the resulting secondary particle. It is still unclear where this cosmic neutrino came from and through which process it was created. However, some of the most high -energy events in the cosmos are possible as candidates.
Whether active supermass-rich black holes in galaxies, supernova explosions or gamma-ray outbreaks: they all released great energies and can look like cosmic particle accelerators. They create extremely fast, high -energy particles that make up part of the cosmic radiation. However, where this comes from and what events cause this energy -sufficient part of the cosmic particles is largely unclear. One of the reasons for this: invited particles are repeatedly distracted by magnetic fields on their way through the cosmos, so that they cannot be traced back to their origin. However, this is different with cosmic neutrinos: these particles are almost masselos, unloading and interchanging work with little matter, at the same time they also develop in some of the most energy -reaching events in the cosmos. “Neutrinos are special cosmic messengers that provide us with unique information about the mechanisms of the most energetic phenomena and enable us to explore the outermost areas of the universe,” explains Rosa Coniglione from the Infn, the National Institute of Nuclear Physics in Italy.
Neutrino detectors at the bottom of the Mediterranean
Casing cosmic neutrinos is anything but simple because these elementary particles hardly interact with a different matter. The rare cases of collision of a neutrino with an atom can be detected by the secondary particles generated, including myons. In the event of interaction with matter of energy in the form of tiny flashes of light, these particles freely freed up, which can be absorbed by special photo -stectors. “In order to detect the passage of these invited particles that arise in or near the detector through neutrino interactions, neutrino observatories use very large volume of water or ice,” explains the KM3NET collaboration, the research initiative behind the Kilometr Cube Neutrino Telescope ( Km3net). The challenge is to distinguish the few cosmic, very energetic neutrino signals from those of the far more numerous atmospheric neutrinos.
The most energy-reaching cosmic neutrino signals have so far been captured by the IceCube NeutrinDetector at the South Pole, which uses more than 5000 spherical photodetectors sunk in the ice. Among the finds were an antineutrino with 6.5 peta electron volt and a neutrino with 10 petaelectron volt-this corresponds to the ten-billiren times the energy of an electron. But now astrophysicists have detected an even stronger neutrino signal. This showed itself in one of the two detector fields of the KM3net neutrinDETETTOR still under construction at the bottom of the Mediterranean. These use spherical photodetectors anchored on the sea floor to catch up with the weak bluish Tscherekowlitge of the secondary particles generated by the neutrinos. The Arca measuring field is located off the coast of Sicily at a depth of around 3450 meters and is covered in the finished state 230 around 100 meters from each other. Each of them consists of photodetectors who are arranged on top of each other on hundreds of meters long. The second measuring field, Orca, is located at a depth of 2450 meters off the coast of southern France and will include 115 detector units at a distance of 20 meters each.
Myonspur reveals Ultra-Erergieriches Neutrino
The current neutrino signal was registered on February 13, 2023 by the detectors of the ARCA measuring field, which was only ten percent completed. An energetic myon raced almost horizontally through the detector field and created such a strong Tscherenkow light that the closest photodetectors were oversaturated, as the physicists of the KM3Net collaboration report. More detailed analyzes showed that this myon had an energy of 120 petaelectron volts – a new record. “In view of its enormous energy and almost horizontal direction, this Myon must have arisen by the matter interaction of a neutrino of even higher energy near the detector,” the researchers write. According to their model simulations, the triggering neutrino must have had an energy of 220 petaelectron volts – as much as never before. “A new chapter of neutrino astronomy begins with this first discovery of a neutrino with hundreds of petaelectron volt. A new observation window opens in the universe, ”says KM3NET spokesman Paschal Coyle from the Center for Partchen Physics in Marseille.
According to the researchers, proof of the new record neutrino provides the first proof that neutrinos actually exist in nature. However, where this particle came from is still unclear. The physicists were able to narrow down the sky area from which the neutrino comes. However, comparing with potential copyrights such as gamma -beam outlets, supernovae or active galaxy nuclei did not provide any clear spatial agreement. There was also no clear result when searching for neutrinos with lower energies that could come from the same source. “A conceivable alternative would also be a cosmogenic neutrino production in which neutrinos are generated by interaction cosmic radiation with excalactic background light or the cosmic microwave background,” explains the team. If the latter was confirmed, the event that was baptized KM3-230213A would be the first proof of such a cosmogenic neutrino.
“The Neutrino KM3-230213A is a remarkable discovery, if only because of its energy, which is more than ten times higher than the next lower, the Icecube and the Pierre-Aucker Observatory have found the search in a decade,” he does not write at the Study involved physicists Erik Blaufuss from the University of Maryland in an accompanying comment in “Nature”. It is all the more remarkable that this neutrino has been detected even before the KM3Net observatory was completed. “Even if it will still take time to fully explore the origins of this event, this is an extraordinary welcome message for km3net,” said Blaufuss. The discovery arouses hope that this detector will capture other cosmic neutrinos of this kind in the near future.
Source: km3net collaboration, nature, DOI: 10.1038/S41586-024-08543-1