Physicists engaged in research in the framework of the OPERA project have recorded the fourth case of an extremely rare event – the transformation of a muon neutrino into a tau neutrino. Thus, the reality of such a process is no longer a hypothesis or an accident, which has only three confirmed cases of neutrino oscillations, but is a proven fact.

The OPERA detector is located in Gran Sasso (Italy) in an underground laboratory. A stream of neutrinos from the CERN accelerator, located 730 km away in Switzerland, rushes towards it through the thickness of the rocks of the Alps. The main task of the detector is to detect neutrino oscillations, that is, the ability of particles to pass into an electronic, muonic or tau-neutrino state.

Oscillations of neutrinos are possible only when the particles have a nonzero mass. Depending on the mass of particles, one can judge the mass of the Universe and have an idea of ​​the scenario for the development of its further fate. Among other things, the non-zero mass of particles can explain why there is so much matter in the universe and practically no antimatter.

If in the flux of muon neutrinos coming from CERN, the OPERA detector registers the appearance of a tau neutrino, then, therefore, the transformation has occurred. Until now, 3 cases of the transformation of muon neutrinos into tau neutrinos have been registered – in 2010, 2012 and 2013. The head of the project, Giovanni de Lellis, noted that the registration of the fourth tau neutrino is an important event confirming the previously observed events.