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- Models with extended Higgs sectors at future e(+)e(-) collidersPublication . Azevedo, Duarte; Ferreira, Pedro Miguel; Muehlleitner, Milada Margarete; Santos, Rui; Wittbrodt, JonasWe discuss the phenomenology of several beyond the Standard Model (SM) extensions that include extended Higgs sectors. The models discussed are the SM extended by a complex singlet field, the 2-Higgs-doublet model with a CP-conserving and a CP-violating scalar sector, the singlet extension of the 2-Higgs-doublet model, and the next-to-minimal supersymmetric SM extension. All the above models have at least three neutral scalars, with one being the 125 GeV Higgs boson. This common feature allows us to compare the production and decay rates of the other two scalars and therefore to compare their behavior at future electron-positron colliders. Using predictions on the expected precision of the 125 GeV Higgs boson couplings at these colliders we are able to obtain the allowed admixtures of either a singlet or a pseudoscalar to the observed 125 GeV scalar. Therefore, even if no new scalar is found, the expected precision at future electron-positron colliders, such as CLIC, will certainly contribute to a clearer picture of the nature of the discovered Riggs boson.
- CP in the darkPublication . Azevedo, Duarte; Ferreira, Pedro Miguel; Muhlleitner, Milada; Patel, Shruti; Santos, Rui; Wittbrodt, JonasWe build a model containing two scalar doublets and a scalar singlet with a specific discrete symmetry. After spontaneous symmetry breaking, the model has Standard Model-like phenomenology, as well as a hidden scalar sector which provides a viable dark matter candidate. We show that CP violation in the scalar sector occurs exclusively in the hidden sector, and consider possible experimental signatures of this CP violation. In particular, we study contribution to anomalous gauge couplings from the hidden scalars.
- pp → A → Zh and the wrong-sign limit of the two-Higgs-doublet modelPublication . Ferreira, Pedro Miguel; Liebler, Stefan; Wittbrodt, JonasWe point out the importance of the decay channels A → Zh and H → VV in the wrong-sign limit of the two-Higgs-doublet model (2HDM) of type II. They can be the dominant decay modes at moderate values of tan β, even if the (pseudo)scalar mass is above the threshold where the decay into a pair of top quarks is kinematically open. Accordingly, large cross sections pp → A → Zh and pp → H → VV are obtained and currently probed by the LHC experiments, yielding conclusive statements about the remaining parameter space of the wrong-sign limit. In addition, mild excesses—as recently found in the ATLAS analysis b¯b → A → Zh—could be explained. The wrong-sign limit makes other important testable predictions for the light Higgs boson couplings.
- The dark phases of the N2HDMPublication . Engeln, Isabell; Ferreira, Pedro Miguel; Muehlleitner, Milada Margarete; Santos, Rui; Wittbrodt, JonasWe discuss the dark phases of the Next-to-2-Higgs Doublet model. The model is an extension of the Standard Model with an extra doublet and an extra singlet that has four distinct CP-conserving phases, three of which provide dark matter candidates. We discuss in detail the vacuum structure of the different phases and the issue of stability at tree-level of each phase. Taking into account the most relevant experimental and theoretical constraints, we found that there are combinations of measurements at the Large Hadron Collider that could single out a specific phase. The measurement of h(125) -> gamma gamma together with the discovery of a new scalar with specific rates to tau (+)tau (-) or gamma gamma could exclude some phases and point to a specific phase.