OBTAINING KAPPA-]PI-PI FROM OFF-SHELL KAPPA-]PI AMPLITUDES

We properly define off-shell K --> pi transition amplitudes and use th em to extract information for on-shell K --> pi pi amplitudes within C hiral Perturbation Theory. At order p(2) in the chiral expansion all t hree parameters of weak interaction can be determined. At order p(4) w e are able to fix eleven additional constants out of thirteen contribu ting to off-shell K --> pi transitions, which leaves four undetermined constants in the on-shell K --> pi pi amplitudes. All O (p(4)) contri butions have been exactly derived with m(pi)(2) not equal 0. We finall y discuss the weak mass term issue and find contributions to on-shell Delta S = +/- 1 kaon decays, in particular to transitions like K-L --> gamma gamma, K-L --> mu(+) mu(-) and K-S --> pi(0)gamma gamma at the lowest non-zero order. (C) 1998 Elsevier Science B.V.