Binary Systems in Qm and in Qft: Cpt

Quasi-degenerate neutral systems like a (K, K̄) type are investigated in Quantum Field Theory (QFT). A constant mass matrix as the one used in Quantum Mechanics (QM) can only be introduced as a linear approximation to QFT. We study the phenomenological consequences of the differences between the QFT and QM treatments. The role of “spurious” states with zero norm at the poles is emphasized. The KL − KS mass splitting triggers a tiny difference between the CP violating parameters ǫL and ǫS, without any violation of TCP . Non-vanishing semi-leptonic asymmetry δS − δL does not signal TCP violation (usual claims not withstanding), while ATCP keeps vanishing when TCP is good symmetry.