Inverse-Moment Chiral Sum Rules

A general class of inverse-moment sum rules was previously derived by the authors in a chiral perturbation theory (ChPT) study at two-loop order of the isospin and hypercharge vector-current propagators. Here, we address the evaluation of the inverse-moment sum rules in terms of existing data and theoretical constraints. Two kinds of sum rules are seen to occur, those which contain as-yet undetermined ${\cal O}(q^6)$ counterterms and those free of such quantities. We use the former to obtain phenomenological evaluations of two ${\cal O}(q^6)$ counterterms. Light is shed on the important but difficult issue regarding contributions of higher orders in the ChPT expansion.