The Applicability of the Equivalence Theorem in $χPT$

Abstract

We have explicitely calculated the tree level elastic scattering cross sections of two longitudinal gauge bosons, up to four derivatives in the chiral expansion both with and without using the Equivalence Theorem (ET). The numerical results show the existence of new and severe restrictions in the ET energy applicability range, as it was stated in our recent derivation, which we also review here, of the precise ET version in the Chiral Lagrangian description of the Standard Model Symmetry Breaking Sector.