Chiral weak dynamics

Abstract

We derive a chiral weak Lagrangian which interpolates the QCD-corrected-four-fermion weak-interaction Lagrangian to low energies. This is done using the Nambu--Jona-Lasinio model as a guide. The derivation treats SU(3) breaking from the current-quark mass on an equal footing with the spontaneous chiral-symmetry breaking. It leads naturally to an additional factor of 2--4 enhancement of \ensuremath{\Delta}I=1/2 K\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\pi} decay amplitudes.