Reacción a "Highest-energy cosmic neutrino detected to date"

With only 10% of its final size in operation, the KM3NeT/ARCA experiment has detected the most energetic neutrino observed to date, with an energy 30 times higher than that of neutrinos previously recorded by the IceCube neutrino telescope at the South Pole.  

The article published by the international collaboration KM3NeT contains a rigorous study, which analyzes in depth the main properties of the detected event, such as its energy and direction of arrival, as well as the possible origin of the neutrino that triggers the observed signal.  

To date, neutrinos of such high energies have not been observed, which suggests that this type of neutrino is not very abundant. This work analyzes the coherence of the detected signal with the absence of detections in other experiments, such as the neutrino telescopes IceCube (located at the South Pole) and ANTARES (predecessor of KM3NeT) or the Pierre Auger cosmic ray detector (in Argentina). According to these previous results, one would expect to observe only one event such as the one recorded in 70 years of operation of the KM3NeT experiment. Even so, it is estimated that the observed signal would be a statistical fluctuation compatible with the previous results. This observation is, therefore, the first evidence of the existence of neutrinos with extremely high energies in nature.  

In addition to its energy, another crucial aspect addressed by this study is the origin of the observed signal. According to the analysis presented, it is unlikely to have been generated by a muon or an atmospheric neutrino, which points to a possible cosmic origin. In such a case, it could be a cosmic neutrino coming from an astrophysical accelerator, such as an active galactic nucleus (AGN), or a cosmogenic neutrino, produced in the interaction of cosmic rays with the photons of the cosmic microwave background. The latter type of neutrino has not yet been detected, which highlights the relevance of the observation made.  

The main limitation of this work lies in the difficulty of identifying the origin of the signal, especially when only one neutrino is available. The search in different catalogs has not revealed any transient source coincident with the event, but it has allowed us to identify up to 12 blazars (a type of AGN) in its vicinity, which could be the origin of the emission. However, for the time being, this result is not conclusive. The full installation of KM3NeT/ARCA will significantly increase the detector's sensitivity to very high energy events, thus improving its ability to identify the sources of these cosmic neutrinos.