309 resultados para abelian Higgs


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Pós-graduação em Física - FEG

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Searches are presented for heavy scalar (H) and pseudoscalar (A) Higgs bosons posited in the two doublet model (2HDM) extensions of the standard model (SM). These searches are based on a data sample of pp collisions collected with the CMS experiment at the LHC at a center-of-mass energy of root s = 8 TeV and corresponding to an integrated luminosity of 19.5 fb(-1). The decays H -> hh and A -> Zh, where h denotes an SM-like Higgs boson, lead to events with three or more isolated charged leptons or with a photon pair accompanied by one or more isolated leptons. The search results are presented in terms of the H and A production cross sections times branching fractions and are further interpreted in terms of 2HDM parameters. We place 95% C.L. cross section upper limits of approximately 7 pb on sigma B for H -> hh and 2 pb for A -> Zh. Also presented are the results of a search for the rare decay of the top quark that results in a charm quark and an SM Higgs boson, t -> ch, the existence of which would indicate a nonzero flavor-changing Yukawa coupling of the top quark to the Higgs boson. We place a 95% C.L. upper limit of 0.56% on B(t -> ch).

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The effect of new operators that only modify the bosonic couplings of the Higgs boson, without altering the WW gamma or WWZ three-point functions, are examined in the e(+)e(-) --> ZZ gamma and Z gamma gamma processes. We analyse the constraints on these interactions that can be imposed by the LEP II collider at CERN and at the Next Linear Collider. (C) 1998 Elsevier B.V. B.V.

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We estimate the attainable limits on the coupling of a nonstandard Higgs boson to two photons taking into account the data collected by the Fermilab collaborations on diphoton events. We based our analysis on a general set of dimension-6 effective operators that give rise to anomalous couplings in the bosonic sector of the standard model. If the coefficients of all blind operators have the same magnitude, indirect bounds on the anomalous triple vector-boson couplings can also be inferred, provided there is no large cancellatton in the Higgs-gamma-gamma coupling.

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Higgs bosons can have a substantial invisible branching ratio in many extensions of the Standard Model, such as models where the Higgs bosons decay predominantly into light or massless weakly interacting Goldstone bosons. In this work, we examine the production mechanisms and backgrounds for invisibly decaying Higgs bosons at the Next Linear e+e- Collider operating in the modes e+e-, eγ, and γγ. We demonstrate that such machine is much more efficient to survey for invisibly decaying Higgs bosons than the Large Hadron Collider at CERN.

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We study the effect of anomalous Hγγ and HZγ couplings, described by a general effective Lagrangian, on the process e+e-→bb̄γ at CERN LEP 2 energies. We include the relevant irreducible standard model background to this process, and from the photon energy spectrum, we determine the reach of LEP 2 to unravel the anomalous couplings by analyzing the significance of the signal for a Higgs boson with a mass up to 150 GeV.