Two-loop improved predictions for $$\ bf {sin^2\theta _{eff}}$$ sin 2 θ eff in Two-Higgs-Doublet models

Abstract We present the currently most precise predictions for the W-boson mass and the leptonic effective mixing angle 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 $$\tan \beta $$ tan β and the soft $$Z_2$$ Z 2 -symmetry breaking parameter $$m_{12}^2$$ 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 result of the CDF collaboration. Numerical results are shown for the dependence on the various non-standard parameters and in comparison with experimental data.