ar X iv : h ep - l at / 0 30 80 10 v 1 1 1 A ug 2 00 3 1 UW - PT 03 - 12 Extending the Utility of Partially Quenched QCD ∗

It has been proposed that partially quenched chiral perturbation theory can be used together with partially quenched lattice QCD to determine the low-energy constants of real QCD. We point out a complication of this approach and show how it can be resolved. Partial quenching changes the chiral symmetry group and introduces a new independent four-derivative operator. We explore the effects of this new operator. We describe tree-level scattering processes to which it contributes, and show how they can be used, in principle, to deterimine its unknown coefficient. We also calculate its lowest-order (one-loop) contribution to charged meson masses and decay constants. In addition, we present the form of the analytic next-to-next-to-leading order meson mass and decay constant corrections, which are needed for lattice fits.