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Modelo Lepto-fóbico com um bóson Z : Análise sobre possível evidência de matéria escura.Oliveira, Jardson Ricardo de Souza 01 March 2013 (has links)
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Previous issue date: 2013-03-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The Standard Model with its current simmetry, is complete, but still not the
final word for the study of elementary particle physics, and many of the experiments
show an accumulation of data indicating the existence of DarkMatter, i.e., new physics
that can not be described only by it; in mid-2009 , an excess in the fraction of the flow of
electron/positron experiments measured by the PAMELLA[1], FERMI[2] and HESS[3],
experiments that could be interpreted as possible evidence of dark matter annihilation
through Lepto-phobic interaction, instigated researchers. Therefore, to describe such
a scenario, the following will consider the extension of the standard model with the
gauge group ULi−Lj (1)[4], for an analysis of how this can help solve this problem of
excessive flow detected. / O Modelo Padrão com sua simetria atual, está completo, porém ainda não é a
palavra final para o estudo de física de física das partículas elementares, muitos dos
experimentos realizados apresentam uma acumulação de dados que denotam a existência
de Matéria Escura, ou seja, apontam para física nova que não pode ser descrita
somente por ele; em meados de 2009, um excesso na fração do fluxo elétron/pósitron
medida pelos experimentos do PAMELA[1],FERMI-Lat[2] e HESS[3], que puderam ser
interpretados como possíveis evidências de aniquilação de matéria escura através de
interação lepto-fóbica, instigaram os pesquisadores. Portanto, para descrever tal cenário,
a seguir considerar-se-á a extensão do Modelo Padrão com o grupo de gauge
ULi−Lj (1)[4], para uma análise de como este pode ajudar a resolver esse problema do
fluxo excessivo detectado.
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Search for Higgs boson decays to beyond-the-Standard-Model light bosons in four-lepton events with the ATLAS detector at the LHCChiu, Justin 22 December 2020 (has links)
This thesis presents the search for the dark sector process h -> Zd Zd -> 4l in events collected by the ATLAS detector at the Large Hadron Collider in 2015--2018. In this theorized process, the Standard Model Higgs boson (h) decays to four leptons via two intermediate Beyond-the-Standard-Model particles each called Zd. This process arises from interactions of the Standard Model with a dark sector. A dark sector consists of one or more new particles that have limited or zero interaction with the Standard Model, such as the new vector boson Zd (dark photon). It could have a rich and interesting phenomenology like the visible sector (the Standard Model) and could naturally address many outstanding problems in particle physics. For example, it could contain a particle candidate for dark matter. In particular, Higgs decays to Beyond-the-Standard-Model particles are well-motivated theoretically and are not tightly constrained; current measurements of Standard Model Higgs properties permit the fraction of such decays to be as high as approximately 30%. The results of this search do not show evidence for the existence of the h -> Zd Zd -> 4l process and are therefore interpreted in terms of upper limits on the branching ratio B(h -> Zd Zd) and the effective Higgs mixing parameter kappa^prime. / Graduate
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