Chiral perturbation theory

Chiral perturbation theory (ChPT) is an effective field theory constructed with a Lagrangian consistent with the (approximate) chiral symmetry of quantum chromodynamics (QCD), as well as the other symmetries of parity and charge conjugation.^[1] ChPT is a theory which allows one to study the low-energy dynamics of QCD on the basis of this underlying chiral symmetry.