On the Mass of Neutrinos in Flavour State

In this article the relationships are revealed between the views on neutrinos as they show up in various approaches of study. Among these are (a) Fermi’s theory on beta decay, (b) the classical view on the decay of the pion into a muon and a muon neutrino, (c) instrumental attempts for direct measurements of the neutrino’s rest mass like in the KATRIN project, (d) the studies in modern neutrino observatories on the phenomenon of neutrino oscillation and (e) the view on neutrinos in the Structural Model of particle physics. A non-classical kinematic analysis on lab frame decay processes shows that the effective masses of the three neutrinos are the same, although in this respect the comparison with the present data in the PMNS theory is not fully conclusive. Adopting the hypothesis that neutrinos fly at the lab frame speed of pions in free flight, their rest masses have to be set at about 80 meV/c2.