Abstract
Abstract We revisit the electroweak precision tests for Higgsless models of strong EWSB. We use the Vector Meson Dominance approach and express S and T via couplings characterizing vector and axial spin-1 resonances of the strong sector. These couplings are constrained by the elastic unitarity and by requiring a good UV behavior of various form- factors. We pay particular attention to the one-loop contribution of resonances to T (beyond the chiral log), and to how it can improve the fit. We also make contact with the recent studies of Conformal Technicolor. We explain why the second Weinberg sum rule never converges in these models, and formulate a condition necessary for preserving the custodial symmetry in the IR.
Highlights
We revisit the electroweak precision tests for Higgsless models of strong EWSB
Phenomenology taking into account tree-level exchanges of V and A resonances in the goldstone scattering amplitudes and in their coupling to the Standard Model (SM) gauge fields is known as Vector Meson Dominance (VMD) [3, 27]
We considered one vector (V ) and one axial (A) spin-1 resonance and assumed Vector Meson Dominance, i.e. that tree level exchanges of these resonances cure the UV behavior of various formfactors, of the current two point functions, and of the elastic WLWL scattering up to the cutoff Λ ∼ 2MV
Summary
Corrections to the electroweak precision observables can occur via the weak boson selfenergies (oblique, or universal corrections), or in fermion-weak boson vertices. The ε’s are linearly related to the precision observables ∆ρ, ∆k, and ∆rw by universal coefficients dependent only on sW , the sine of the Weinberg angle The latter observables describe genuine electroweak corrections beyond the running of αEM. For the Standard Model (SM), comparison of theory and experiment points to a relatively light Higgs boson This well known fact is demonstrated in figure 1. Electroweak precision analysis is simplified by focussing on the deviations of ε1,3 from their values in the SM for a reference value of the Higgs mass. These deviations are known as the T and S parameters:. Where the approximations are valid if the model is heavy and MHref MZ
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