Two-loop analysis of vector-current propagators in chiral perturbation theory Original Research Article

We perform a calculation of the isospin and hypercharge vector-current propagators (ΔV33μν(q2) and ΔV88μν(q2)) to two loops in chiral perturbation theory. The analysis is carried out with straight-forward Feynman diagram methods by making appropriate use of external vector sources. Counterterms from the O(q6) chiral lagrangian, 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 function with data and the construction of new chiral sum rules.