Gasser-Leutwyler coefficients from partially quenched lattice QCD Original Research Article

We present the latest results of our ongoing project to determine the Gasser-Leutwyler coefficients of the QCD chiral Lagrangian using partially quenched lattice QCD with three flavors of light dynamical quarks. We are currently studying the mass dependence of the pseudoscalar meson and can extract 2L8 − L5 and 2L6 − L4. Neither combination can be determined from experimental data alone. While phenomenological estimates have been available for some time, precise ab initio determination of these low energy constants could greatly reduce the theoretical uncertainties of chiral perturbation theory calculations. Our value of 2L8 − L5 is particularly interesting because it rules out the possibility that a massless up quark is responsible for strong CP invariance. We will discuss in some detail the studies we have done to estimate the theoretical uncertainties of our simulations.