ANATOMY OF A WEAK MATRIX ELEMENT

Although the weak nonleptonic amplitudes of the Standard Model are not oriously difficult to calculate, we have produced a modified weak matr ix element which can be analyzed using reliable methods. This hypothet ical nonleptonic matrix element is expressible in terms of the isovect or vector and axialvector spectral functions rho(V) (s) and rho(A) (s) , which can be determined in terms of data from tau lepton decay and e +e- annihilation. Chiral symmetry and the operator product expansion a re used to constrain the spectral functions respectively in the low en ergy and the high energy limits. The magnitude of the matrix element t hus determined is compared with its ''vacuum saturation'' estimate, an d in the future may be accessible with lattice calculations.