First Order Renormalization of the Weak Magnetic Form-factor Due to Symmetry Breaking*

A sum rule similar to that of Fubini, Furlan and Rosse tti is used to show that the weak magnetic form-factor in strangeness changing semi-leptonic hyperon decays is renormalized to first order in the symmetry breaking Hamiltonian. This is in contrast to the Ademello-Gatto theorem which states that there is no such renormalization in the case of the strangeness changing charge form-factor. (Submitted to Phys. Rev. Letters.) t Work supported by the U. S. Atomic Energy Commission. There is increasing experimental interest in the measurement of the weak magnetic form-factor in semi-leptonic hyperon decays. 1 This paper will argue that we should not expect very close agreement of these form-factors with their SU(3) symmetry values. We start by considering the matrix element between the baryon octet states /o@)> and [BIG)> of the i’th component of the SU(3) vector current;