Top-antitop production from W_(L)^(+)W_(L)^(-) and Z_(L)_Z(L) scattering under a strongly interacting symmetry-breaking sector

Abstract

By considering a non-linear electroweak chiral Lagrangian, including the Higgs, coupled to heavy quarks, and the equivalence theorem, we compute the one-loop scattering amplitudes W^(+)W^(−) → tṫ, Z Z → tṫ and hh → tṫ (in the regime M^(2)_(t)/v^(2) « √sM_(t)/v^(2) « s/v^(2) and to NLO in the effective theory). We calculate the scalar partial-wave helicity amplitudes which allow us to check unitarity at the perturbative level in both M_(t) /v and s/v. As with growing energy perturbative unitarity deteriorates, we also introduce a new unitarization method with the right analytical behavior on the complex s-plane and that can support poles on the second Riemann sheet to describe resonances in terms of the Lagrangian couplings. Thus we have achieved a consistent phenomenological description of any resonant tṫ production that may be enhanced by a possible strongly interacting electroweak symmetry breaking sector.