Global Electroweak Fit Constraints on the Two-Higgs-Doublet Model in Light of the CDF W -Boson Mass

Abstract

The recent measurement of the $W$ boson mass by the CDF II collaboration exhibits a significant tension with the Standard Model (SM) prediction and other experimental determinations. In this work, we investigate the implications of this result within the framework of the Two-Higgs-Doublet Model (2HDM), focusing on radiative corrections to electroweak precision observables parameterized in terms of the oblique parameters $ΔS$, $ΔT$, and $ΔU$. Using global electroweak fits, we analyze how the inclusion of the CDF measurement modifies the preferred parameter space. We show that the observed shift in $m_W$ can be accommodated in the 2HDM through enhanced contributions to $ΔT$, arising from mass splittings in the scalar sector. The resulting constraints on the scalar spectrum are presented and compared with those obtained using previous electroweak data. These results highlight the role of precision observables in probing extended Higgs sectors and provide updated bounds on viable 2HDM parameter space.

Figures (20)

• Figure 1: Input parameters and best-fit values from the global electroweak fit, with the Fermi constant $G_F = 1.1663787(6) \times 10^{-5} \, \mathrm{GeV}^{-2}$Zyla:2020zbs fixed in the analysis. Correlations among $(m_Z, \Gamma_Z, \sigma_h^0, R_\ell^0, A_\ell, A_{\mathrm{FB}}^\ell)$ and $(A_{\mathrm{FB}}^c, A_{\mathrm{FB}}^b, A_c, A_b, R_c, R_b)$ are included as in Ref. Schael2006. The “Pull” is defined as $(O_{\mathrm{fit}} - O_{\mathrm{measure}})/\sigma_{\mathrm{measure}}$, where $\sigma_{\mathrm{measure}}$ is the experimental uncertainty. This table is adapted from Ref. Lu:2022. $^{\fcolorbox{olive}{white}{a}}$ Computed with $\alpha_s$ evaluated at the $Z$ boson mass scale. $^{\fcolorbox{olive}{white}{b}}$ A theoretical uncertainty of $0.5\,\mathrm{GeV}$ has been included. Roman source labels indicate the origin of the experimental inputs: $\mathrm{I}$Zyla:2020zbs; $\mathrm{II}$Crivellin2020Davier2020Keshavarzi2020; $\mathrm{III}$Schael2006; $\mathrm{IV}$Aaltonen:2018dxj.
• Figure 2: Comparison of pull values, $(O_{\mathrm{fit}}-O_{\mathrm{meas}})/\sigma_{\mathrm{meas}}$, for the main electroweak precision observables in global fits using the PDG 2021 (blue) and CDF 2022 (orange) values of the $W$-boson mass. The figure shows that the CDF result induces correlated shifts in multiple observables, rather than a single isolated deviation. This pattern is consistent with the need for positive oblique corrections, especially in $\Delta T$, as expected from custodial-symmetry-breaking effects in extended scalar sectors. The numerical pulls correspond to those shown in Fig. \ref{['fig:EWfit']}.
• Figure 3: Allowed regions at $1\sigma$ and $2\sigma$ confidence levels in the $S$--$T$ plane. The green contours correspond to the PDG 2021 dataset using the previous $m_W$ value, while the red contours include the updated CDF 2022 measurement. The observed upward shift in $T$ suggests possible new physics effects, consistent with our findings and those reported in Lu:2022.
• Figure 4: Allowed regions at $1\sigma$ and $2\sigma$ confidence levels in the $S$--$U$ plane, derived from electroweak fits. The blue contours correspond to the PDG 2021 dataset using the previous $m_W$ value, while the red contours include the updated CDF 2022 measurement. The inclusion of the CDF result leads to a visible positive shift in $U$, while $S$ remains approximately stable. The Standard Model prediction, corresponding to $(S,U) = (0,0)$, is indicated by the black cross at the origin.
• Figure 5: Allowed regions at $1\sigma$ and $2\sigma$ confidence levels in the $T$--$U$ plane, derived from electroweak fits using the global fit results of Table \ref{['tab:STUresult']}. The blue contours correspond to the PDG 2021 dataset using the previous $m_W$ value, while the red contours include the updated CDF 2022 measurement. The inclusion of the CDF result leads to a positive shift in $U$, while $T$ remains essentially unchanged. The Standard Model prediction, corresponding to $(T,U) = (0,0)$, is indicated by the black dot at the origin.