HIGHER-ORDER CORRECTIONS TO SIRLINS THEOREM IN O(P(6)) CHIRAL PERTURBATION-THEORY

We present the results of the first two-loop calculation of a form fac tor in full SU(3) X SU(3) chiral perturbation theory. We choose a spec ific linear combination of pi(+), K+, K-0, and K pi form factors (the one appearing in Sirlin's theorem) which does not get contributions fr om order p(6) operators with unknown constants. For the charge radii, the corrections to the previous one-loop result turn out to be signifi cant. To clearly identify the two-loop effects, more accurate measurem ents of the kaon and pion electromagnetic charge radii would be desira ble.