Multi-Higgs Phenomenology at LHC and Beyond

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Organizational Unit

Publications

Search for an invisible scalar in tt¯ final states at the LHC

Publication . Azevedo, Duarte; Capucha, Rodrigo; Chaves, Pedro; Martins, João Bravo; Onofre, A.; Santos, Rui

We use the current tt¯ experimental analysis to look for Dark Matter (DM) particles hidden in the final state. We present a phenomenological study where we successfully perform the reconstruction of a tt¯ system in the presence of a scalar mediator Y 0, that couples to both Standard Model (SM) and to DM particles. We use a MadGraph5_aMC@NLO simplified DM model, where signal samples of pp → tt¯ Y 0 are generated at the Large Hadron Collider (LHC) with both Charge-Parity (CP) -even and CP-odd couplings of Y 0 to the top quarks. Different mass scales for the Y 0 mediator are considered, from the low mass region (~ 0 GeV) to masses close to the Higgs boson mass (125 GeV). The dileptonic final states of the tt¯ system were used in our analysis. The reconstruction of the tt¯ system is done with a kinematic fit, without reconstructing the mediator. All relevant SM backgrounds for the dileptonic tt¯ search at the LHC are considered. Furthermore, CP angular observables were used to probe the CP-nature of the coupling between the mediator and top-quarks, which allowed to set confidence level (CL) limits for those Yukawa couplings as a function of the mediator mass.

2023Journal article

Open access

Precision muon-related observables as a tool to constrain new physics models

Publication . Lourenço, Gabriel; Milagre, André; Santos, Rui; Silva, Joao

We propose a set of precision muon-related observables that serve as a tool to constrain new physics models. Using LEP's precision measurements on the Z-boson pole, we derive bounds on the new physics quantum contributions to the decay Z -> mu+mu(-). We show that the new precision observables have a real impact on two specific models that solve the g - 2 anomaly and provide a sound dark matter candidate.

2024-07Journal article

Restricted access

New symmetries of the two-Higgs-doublet model

Publication . Ferreira, Pedro Miguel; Grzadkowski, B.; Ogreid, O. M.; Osland, P.

The Two Higgs Doublet Model invariant under the gauge group \(SU(2)\times U(1)\) is known to have six additional global discrete or continuous symmetries of its scalar sector. We have discovered regions of parameter space of the model which are basis and renormalization group invariant to all orders of perturbation theory in the scalar and gauge sectors, but correspond to none of the hitherto considered symmetries. We therefore identify seven new symmetries of the model and discuss their phenomenology. Soft symmetry breaking is required for some of these models so that electroweak symmetry breaking can occur. We show that, at least at the two-loop level, it is possible to extend some of these symmetries to include fermions.

2024-03-06Journal article

Open access