Equivalence theorem and probing the electroweak symmetry-breaking sector

We examine the Lorentz noninvariance ambiguity in longitudinal weak-boson scatterings and the precise conditions for the validity of the equivalence theorem (ET). Safe Lorentz frames for applying the ET are defined, and the intrinsic connection between the longitudinal weak-boson scatterings and probing the symmetry-breaking sector is analyzed. A universal precise formulation of the ET is presented for both the standard model and the chiral Lagrangian formulated electroweak theories. It is shown that in electroweak theories with a strongly interacting symmetry-breaking sector, the longitudinal weak-boson scattering amplitude under proper conditions can be replaced by the corresponding Goldstone-boson scattering amplitude in which all the internal weak-boson lines and fermion loops are ignored.