Stephan Hessenberger | Searcharxiv

arXiv2022

Two-loop improved predictions for $M_W$ and $\sin^2θ_{eff}$ in Two-Higgs-Doublet Models

We present the currently most precise predictions for the $W$-boson mass and the leptonic effective mixing angle $\sin^2θ_{\text{eff}}$ in the aligned Two-Higgs-Doublet Model. The evaluation includes the full one-loop result, all known higher-order corrections of the Standard Model, and the non-standard two-loop contributions that increase with mass splittings between charged and neutral THDM Higgs bosons. They depend on $\tanβ$ and the soft $Z_2$-symmetry breakingparameter $m_{12}^2$ of the scalar potential, in addition to the non-standard boson masses. Whenever the one-loop corrections become large, the two-loop contributions yield substantial modifications of the predictions, which is of particular importance for the $W$ mass where large mass shifts are required to reach the recently published final resultof the CDF collaboration. Numerical results are shown for the dependence on the various non-standard parameters and in comparison with experimental data.

hep-ph↗

arXiv2017

Two-loop corrections to the $ρ$ parameter in Two-Higgs-Doublet Models

Models with two scalar doublets are among the simplest extensions of the Standard Model which fulfill the relation $ρ= 1$ at lowest order for the $ρ$ parameter as favored by experimental data for electroweak observables allowing only small deviations from unity. Such small deviations $Δρ$ originate exclusively from quantum effects with special sensitivity to mass splittings between different isospin components of fermions and scalars. In this paper the dominant two-loop electroweak corrections to $Δρ$ are calculated in the $CP$-conserving THDM, resulting from the top-Yukawa coupling and the self-couplings of the Higgs bosons in the gauge-less limit. The on-shell renormalization scheme is applied. With the assumption that one of the $CP$-even neutral scalars represents the scalar boson observed by the LHC experiments, with standard properties, the two-loop non-standard contributions in $Δρ$ can be separated from the standard ones. These contributions are of particular interest since they increase with mass splittings between non-standard Higgs bosons and can be additionally enhanced by $\tanβ$ and $λ_5$, an additional free coefficient of the Higgs potential, and can thus modify the one-loop result substantially. Numerical results are given for the dependence on the various non-standard parameters, and the influence on the calculation of electroweak precision observables is discussed.

hep-ph↗