  Due to the gap between the known 100 GeV scale and new physics if any, it is
natural to employ an effective one-loop Lagrangian (HEFT) for the particles of
the Electroweak Symmetry Breaking Sector (W_L, Z_L and h). To describe any new
particles and resonances that may be found at the LHC we employ its unitarized
amplitudes, valid even in the presence of new strong interactions. We have
assessed the systematics by comparing several such methods, and find that they
give qualitatively similar results and succesfully produce unitary amplitudes
in the nonperturbative regime. We are thus in a position to describe new
physics in the 0.5 TeV-3 TeV (region of validity of our approximations: the
effective theory and the equivalence theorem to substitute W_L, Z_L by the
Goldstone bosons of electroweak symmetry breaking). We have also computed the
coupling of the EWSBS to the top-antitop and two-photon channels to describe
resonances that decay through them or to study their photon-photon production,
for example. The approach is universal and useful for many BSM theories at low
energy.
