Estimation of oblique electroweak corrections

Abstract

We review the general analysis of the contributions of electroweak vacuum polarization diagrams to precision experiments. We first, review the representation of these contributions by three parameters S, T, and U, and discuss the assumptions involved in this reduction. We then discuss the contributions to these parameters from various models of new physics. We show that S can be computed by a dispersion relation, and we use this technique to estimate S in technicolor models of the Higgs sector. We discuss the reliability and the gauge invariance of this estimate.Finally, we present the limits on S and T imposed by current experimental results.

Higgs-Z-photon coupling from effect of composite resonances

“…In our analysis, we are going to adopt the notation in ref. [18,19], which are rescaled by S = 4s 2 wŜ /α and T =T /α compared with the notation employed in ref. [20].…”

Light charged Higgs at the beginning of the LHC era

“…However, too large λ i leads to the breakdown of perturbation theory [6 -8]. Furthermore, low energy precision data also impose important constraints on the model parameters [9]. We take into account the following bounds to constrain the 2HDM parameters: 1 (i) Perturbative unitarity [6], corresponding to |a 0 (ϕ A ϕ B → ϕ C ϕ D )| < ξ (we take ξ = 1/2 in our analysis), where a 0 (ϕ A ϕ B → ϕ C ϕ D ) is the S-wave amplitude for the elastic scattering process ϕ A ϕ B → ϕ C ϕ D of the longitudinally polarized gauge bosons (and Higgs bosons).…”

“…(ii) Vacuum stability [11] (iii) Constraints on oblique-corrections from LEP with the S, T and U parameters [9]. In particular, the T parameter is such that T ≃ α −1 EM ∆ρ, with ∆ρ ≤ 10 −3 .…”

Higgs phenomenology in the Minimal Dilaton Model after Run I of the LHC

“…We calculate the Peskin-Takeuchi S and T parameters [60] with the formulae presented in [41], and construct χ 2 ST with the following experimental fit results [61]:…”