THEOREM ON FORM FACTORS IN KL3 DECAY

We derive a formula for the matrix element K|μFaμ|π correct up to second order in both the momentum transfer t and the breaking of SU(3) SU(3) symmetry. This leads to a prediction that ξ is very small compared with unity. Our result is independent of any assumption concerning the structure of the symmetry-breaking Hamiltonian. © 1969 The American Physical Society.