Chiral Lagrangian parameters for scalar and pseudoscalar mesons

The results of a high-statistics study of scalar and pseudoscalar meson propagators in quenched lattice QCD are presented. For two values of lattice spacing, $\beta =5.7\mathrm{}\left(a\approx .18\mathrm{fm}\right)$ and 5.9 $\left(a\approx .12\mathrm{fm}\right),$ we probe the light quark mass region using clover improved Wilson fermions with the modified quenched approximation pole-shifting ansatz to treat the exceptional configuration problem. The quenched chiral loop parameters $m_0$ and ${\alpha }_{\Phi }$ are determined from a study of the pseudoscalar hairpin correlator. From a global fit to the meson correlators, estimates are obtained for the relevant chiral Lagrangian parameters, including the Leutwyler parameters $L_5$ and $L_8.$ Using the parameters obtained from the singlet and nonsinglet pseudoscalar correlators, the quenched chiral loop (QCL) effect in the nonsinglet scalar meson correlator is studied. By removing this QCL effect from the lattice correlator, we obtain the mass and decay constant of the ground state scalar, isovector meson $a_0.$