Signature of the 2HDM at Higgs factories

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The full one-loop corrections, both the weak and QED corrections, to the process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}Z\ensuremath{\phi}$ ($\ensuremath{\phi}={h}^{0},{H}^{0}$) in the two-Higgs-doublet model (2HDM) at the Higgs factories are presented. Up to the $O({\ensuremath{\alpha}}_{\mathrm{em}})$ level, the virtual corrections are evaluated by using the feynarts/formcalc packages. The real emission corrections are computed using the Feynman Diagram Calculation (FDC) package, and the collinear divergences are regularized by the electron structure functions. Using the feynarts/formcalc and FDC packages, we study the corrections in the Standard Model (SM) and the 2HDM, respectively. Gauge dependence arising in the renormalization of mixing angels is removed by using the pinch technique. After taking into account experimental constraints from the current LHC data, we propose four interesting benchmark scenarios for future colliders. By using these benchmark scenarios, we evaluate the deviation of $\mathrm{\ensuremath{\Delta}}\ensuremath{\sigma}({e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}Z\ensuremath{\phi})$ from their SM values. We also examine Higgs boson decays $\ensuremath{\phi}\ensuremath{\rightarrow}b\overline{b}$ and $\ensuremath{\phi}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$, which can have large electroweak (EW) contributions from triple Higgs couplings which are absent in the SM. It is found that for these benchmark scenarios, both EW and real emission corrections are sizeable and could be measured at future ${e}^{+}{e}^{\ensuremath{-}}$ colliders such as the ILC, CLIC, and CEPC.