Speaker
Description
The 2HDM+S is the singlet extension of Two-Higgs-Doublets Model (2HDM), where the additional singlet-like particles can accommodate more physics potential beyond the Standard Model (SM), e.g. the dark matter candidate, as well as match to the Higgs sector of Next-to Mnimal-supersymmetric Standard model (NMSSM). The BSM extension of the Higgs sector can contribute the self-energy of $W^\pm$ and $Z$ bosons additionally, while the singlet field can enter as well via the mixing between the singlet and doublet fields. In this work, we focus on the electroweak precision observables $STU$, which are sensitive to the BSM effect on the $W^\pm$ and $Z$ self-energy. We disentangle the $3\times 3$ mixing system in the CP-even sector of the 2HDM+S and discuss the impact of singlet admixture in five fundamental cases, where only one mixing angles is opened and the others are decoupled. Eventually, we found the distinctive behaviour of the $STU$ observables in the 2HDM+S compared to 2HDM. In particular, we obtain serval mass relations, e.g. $c^2_{\alpha_{HS}} m_{H} + s^2_{\alpha_{HS}}m_{h_S} = m_{H^\pm}$, which can ensure that the $STU$ limits is fulfilled.
