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 tbar{t}, ZZrightarrow tbar{t} and hhrightarrow tbar{t} (in the regime M_t^2/v^2ll sqrt{s}M_t/v^2ll 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 tbar{t} production that may be enhanced by a possible strongly interacting electroweak symmetry breaking sector.
Highlights
The Higgs-like particle with a mass of 125 GeV found at the Large Hadron Collider (LHC) [1,2] completes a possible framework of the fundamental interactions, as this new boson has quantum numbers and couplings compatible with those expected for the Higgs of the Standard Model (SM) in its minimal version
The discrepancy among the Higgs mass scale and that of any new-physics appearance is suggestive of a Goldstoneboson (GB) interpretation of the Higgs boson that may be related to some global spontaneous symmetry breaking that in turn prompts a breaking of the electroweak gauge symmetry SU (2)L ×U (1)Y → U (1)Q
As the Higgs Effective Field Theory (HEFT) theories are derivative expansions, for most of parameter space, the interactions will generically become strong at sufficiently high energy, and we have argued that a second, very broad scalar pole is expected [26,27]
Summary
The Higgs-like particle with a mass of 125 GeV found at the Large Hadron Collider (LHC) [1,2] completes a possible framework of the fundamental interactions, as this new boson has quantum numbers and couplings compatible with those expected for the Higgs of the Standard Model (SM) in its minimal version. As the HEFT theories are derivative expansions, for most of parameter space (saliently excluding that of the Standard Model and perhaps other very carefully tuned sets), the interactions will generically become strong at sufficiently high energy, and we have argued that a second, very broad scalar pole is expected [26,27].
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