New Physics with Light Mediators

• Autor(a) principal: Silva, Ana Luisa Foguel da
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/43/43134/tde-16052022-204323/
• topic: Beyond Standard Model physics; Dark Higgs; Dark Photon; Física Além do Modelo Padrão; Fótons Escuros; Hidden Abelian Higgs Model; Higgs Escuro; Light Vector Mediators; Mediadores Vetoriais Leves; modelo HAHM

Among the possible beyond the Standard Model (SM) extensions, the addition of a new abelian U(1) gauge group is one of the most minimal and simple models that one can think of. In the secluded scenario, the dark vector boson associated with the extra symmetry interacts with the SM sector via a kinetic mixing term with the hypercharge gauge boson, whereas for the generic case we can also afford direct couplings to the SM fermions. In this dissertation we focus on two different studies concerning the U(1) gauge extension. In the first one, following the vector meson dominance approach, we computed, for the first time, vector boson decays into almost arbitrary hadronic final states. The effects of our hadronic improvements lead to substantial modifications on the dark boson decay widths, branching ratios and even on the experimental bounds for some cases. We provide the results of our hadronic implementation in the publicly available python package DeLiVeR. In the second part of this dissertation, we consider an ultraviolet completion to the U(1) extension where a new scalar singlet that mixes with the SM-like Higgs boson and generates the dark boson mass is added. We study the electroweak precision test constraints of such a model as well as the phenomenological implications of two different kind of searches. In the first one, we simulate the signal of the higgs decay into two dark photons, which in turn decay into muons, in order to obtain the ATLAS and CMS bounds on the model parameter space. In the second, we constrain the scalar mixing angle by considering the branching ratio of the invisible kaon decay into a pion as limited by the KOTO experiment.