Determination of the ΔS=1 weak Hamiltonian of the SU(4) chiral limit through topological zero-mode wave functions

Abstract

A new method to determine the low-energy couplings of the ΔS=1 weak Hamiltonian is presented. It relies on a matching of the topological poles in 1/m2 of three-point correlators of two pseudoscalar densities and a four-fermion operator, measured in lattice QCD, to the same observables computed in the ε-regime of chiral perturbation theory. We test this method in a theory with a light charm quark, i.e. with an SU(4) flavour symmetry. Quenched numerical measurements are performed in a 2 fm box, and chiral perturbation theory predictions are worked out up to next-to-leading order. The matching of the two sides allows to determine the weak low-energy couplings in the SU(4) limit. We compare the results with a previous determination, based on three-point correlators containing two left-handed currents, and discuss the merits and drawbacks of the two procedures.