2-LOOP ANALYSIS OF VECTOR-CURRENT PROPAGATORS IN CHIRAL PERTURBATION-THEORY

We perform a calculation of the isospin and hypercharge vector-current propagators (Delta(V33)(mu nu)(q(2)) and Delta(V88)(mu nu)(q(2))) to two loops in chiral perturbation theory. The analysis is carried out w ith straightforward Feynman diagram methods by making appropriate use of external vector sources. Counterterms from the O(q(6)) chiral lagra ngian, required to absorb divergences and scale dependence encountered at the two-loop level, are constructed. Our final results are finite, covariant, and scale-independent Several applications are described, including a comparison of the two-loop isospin vector spectral functio n with data and the construction of new chiral sum rules.