The Limitation of Partially Quenched QCD
Abstract
Processes in lowenergy QCD involving the pseudoscalar mesons can be calculated using SU(3) chiral perturbation theory. Nexttoleadingorder calculations have been done, but the results are in terms of a number of coefficients, the GasserLeutwyler coefficients. Some of these coefficients can be determined from experiment, while others cannot and are known rather poorly. However, one would like to calculate them directly from first principles. Such calculations may be possible using lattice QCD. It has been suggested that using the partially quenched lattice approximation would make them easier. We point out a limitation of this approach. New operators exist in the partially quenched chiral lagrangian due to the different, graded, group structure. Such operators do not contribute to meson masses and decay constants until nexttonexttoleading order. We describe the operator that must be added to the GasserLeutwyler lagrangian in the partially quenched theory. We calculate explicit examples of parameters in which it appears, and show that it vanishes in the unquenched limit.
 Publication:

APS Northwest Section Meeting Abstracts
 Pub Date:
 May 2003
 Bibcode:
 2003APS..NWS.H2008V