We calculate the correlator between two external vector currents having the quantum numbers of a charged kaon. We give the renormalized expression to two loops in standard chiral perturbation theory in the isospin limit, which, as a physical result, is finite and scale independent. Applications include a low energy theorem, valid at two loop order, of a flavor breaking combination of vector current correlators, as well as a determination of the phenomenologically relevant finite ${O(p}^6)$-counterterm combination $Q_V$ by means of inverse moment finite energy sum rules. This determination is less sensitive to isospin-breaking effects than previous attempts.

• Received 29 July 1999

DOI:https://doi.org/10.1103/PhysRevD.61.114025