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.

We study the LHC signatures of new gauge bosons in the gauge-invariant minimal Higgsless model. It predicts an extra pair of W1 and Z1 bosons which can be as light as ∼ 400 GeV and play a key role in the delay of unitarity violation. We analyze the W1 signals in pp → W0Z0Z0 → jj4ℓ and pp → W0Z0jj → ν3ℓjj processes at the LHC, including the complete electroweak and QCD backgrounds. We reveal the complementarity between these two channels for discovering the W1 boson, and demonstrate the LHC discovery potential over the full range of allowed W1 mass.

We study the physics potential of the 8 TeV LHC (LHC-8) to discover, during its 2012 run, a large class of extended gauge models or extradimensional models whose low-energy behavior is well represented by an SUð2Þ 2 Uð1Þ gauge structure. We analyze this class of models and find that, with a combined integrated luminosity of 40-60 fb À1 at the LHC-8, the first new Kaluza-Klein mode of the W gauge boson can be discovered up to a mass of about 370-400 GeV when produced in association with a Z boson.