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- Are there hidden scalars in LHC Higgs results?Publication . Arhrib, A.; Ferreira, Pedro Miguel; Santos, RuiThe Higgs boson recently discovered at the Large Hadron Collider has shown to have couplings to the remaining particles well within what is predicted by the Standard Model. The search for other new heavy scalar states has so far revealed to be fruitless, imposing constraints on the existence of new scalar particles. However, it is still possible that any existing heavy scalars would preferentially decay to final states involving the light Higgs boson thus evading the current LHC bounds on heavy scalar states. Moreover, decays of the heavy scalars could increase the number of light Higgs bosons being produced. Since the number of light Higgs bosons decaying to Standard Model particles is within the predicted range, this could mean that part of the light Higgs bosons could have their origin in heavy scalar decays. This situation would occur if the light Higgs couplings to Standard Model particles were reduced by a concomitant amount. Using a very simple extension of the SM - the two-Higgs doublet model we show that in fact we could already be observing the effect of the heavy scalar states even if all results related to the Higgs are in excellent agreement with the Standard Model predictions.
- Vacuum structure of the Z(2) symmetric Georgi-Machacek modelPublication . Azevedo, Duarte; Ferreira, Pedro Miguel; Logan, Heather E.; Santos, RuiWe discuss the vacuum structure of a version of the Georgi-Machecek model with an exact Z(2) symmetry acting on the triplet fields. Besides the usual custodial-symmetric model, with rho = 1 at tree-level, a model with a dark matter candidate is also viable. The other phases of the model lead to electric charge breaking, a wrong pattern of electroweak symmetry breaking or to rho not equal 1 at tree-level. We derive conditions to have an absolute minimum in each of the two viable phases, the custodial and the dark matter phases.
- 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.