Neutrino oscillations revisited and neutrinoless double beta decay

The theory of neutrino oscillations remains to be an open problem. To address this, a new quantum field theory formalism of neutrino oscillations is advocated. This formalism includes neutrino emission and detection in a second-order Feynman diagram, demonstrates entanglement between the two processes and leads to the expected production rate for Racah's process, which involves the oscillation of neutrinos into antineutrinos (and vice versa). Further, a link between the Majorana masses of neutrinos, which govern the neutrinoless double-beta decay and the process based on neutrino-antineutrino oscillation, is established. It is argued that further investigation is necessary to explore the potential of Racah's process in determining the Majorana nature of neutrinos.