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

Abstract

By using a Non-linear Electroweak Chiral Lagrangian, including the Higgs, coupled to heavy quarks, and the Equivalence Theorem, we compute (in the regime $M_t^2/v^2\ll \sqrt{s}{M}_t/v^2\ll s/v^2$) the one-loop amplitudes $W^{+}{W}^{-}\to t\bar{t}$, $ZZ\to t\bar{t}$ and $hh\to t\bar{t}$ (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 $t\bar{t}$ production that may be enhanced by a possible strongly interacting Electroweak Symmetry Breaking Sector.

Comments: 13 pages, 12 figures