Two-level Friedrichs model and kaonic phenomenology

In the present Letter, we study in the framework of the Friedrichs model the evolution of a two-level system coupled to a continuum. This unitary evolution possesses a non-unitary component with a non-Hermitian effective Hamiltonian. We show that this model is well adapted in order to describe kaon phenomenology (oscillation, regeneration) and leads to a CP violation, although in this case the prediction is not quantitatively quite satisfying.