Neutrino oscillations: A relativistic example of a two-level system

Neutrino flavor oscillations are discussed in terms of an explicit model. This model consists of two coupled Dirac equations with three parameters: the electron neutrino mass, the muon neutrino mass, and a coefficient which describes the possibility that the neutrino can flip flavor. The system is diagonalized to obtain the exact eigenvalues and eigenfunctions. The system is then quantized and the neutrino flavor wave functions are derived directly from the quantized fields. It is shown that neutrino flavor oscillation probabilities are recovered in a quantum field theory treatment only in the ultrarelativistic limit. (C) 1999 American Association of Physics Teachers.