Top–antitop production from $$W^+_L W^-_L$$ W L + W L - and $$Z_L Z_L$$ Z L Z L scattering under a strongly interacting symmetry-breaking sector

Abstract

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 $$W^+W^-\rightarrow t\bar{t}$$ W + W - → t t ¯ , $$ZZ\rightarrow t\bar{t}$$ Z Z → t t ¯ and $$hh\rightarrow t\bar{t}$$ h h → t t ¯ (in the regime $$M_t^2/v^2\ll \sqrt{s}M_t/v^2\ll s/v^2$$ M t 2 / v 2 ≪ s M 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 $$M_t/v$$ 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 $$t\bar{t}$$ t t ¯ production that may be enhanced by a possible strongly interacting electroweak symmetry breaking sector.