Obtaining K → ππ from off-shell K → π amplitudes
We properly define off-shell K → π transition amplitudes and use them to extract information for on-shell K → ππ amplitudes within Chiral Perturbation Theory. At order p2 in the chiral expansion all three parameters of weak interaction can be determined. At order p4 we are able to fix eleven additional constants out of thirteen contributing to off-shell K → π transitions, which leaves four undeter