From kaons to neutrinos: Quantum mechanics of particle oscillations

The problem of particle oscillation is considered in a pedagogical and comp rehensive way. Examples from K, B and neutrino physics are given. Conceptua l difficulties of the traditional approach to particle oscillation are disc ussed. It is shown how the probability current density and the wave packet treatments of particle oscillations resolve some problems. It is also shown that only full field theoretical approach is free from conceptual difficul ties. The possibility of oscillation of particles produced together with ka ons or neutrinos is considered in full wave packet quantum mechanics langua ge. Precise definition of the oscillation of particles which recoil against mixed states is given. The general amplitude which describes the oscillati on of two particles in the final states is found. Using this EPR-type ampli tude the problem of oscillation of particles recoiling against kaons or neu trinos is resolved. The relativistic EPR correlations on distances of the o rder of coherence lengths are considered.