FIELD-THEORY APPROACH TO K-0-(K-0)OVER-BAR AND B-0-(B-0)OVER-BAR SYSTEMS

Quantum field theory provides a consistent framework to deal with unst able particles. We present here an approach based on held theory to de scribe the production and decay of unstable K-0-<(K-0)over bar> and B- 0 -<(B-0)over bar> mixed systems. The formalism is applied to compute the time evolution amplitudes of K-0 and <(K-0)over bar> studied in DA PHNE and CPLEAR experiments. We also introduce a new set of parameters that describe CP violation in K --> pi pi decays without recourse to isospin decomposition of the decay amplitudes.