227,465 research outputs found

    Alternatives to an Elementary Higgs

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    We review strongly coupled and extra dimensional models of electroweak symmetry breaking. Models examined include warped extra dimensions, bulk Higgs, "little" Higgs, dilaton Higgs, composite Higgs, twin Higgs, quantum critical Higgs, and "fat" SUSY Higgs. We also discuss current bounds and future LHC searches for this class of models.Comment: 42 pages, 36 figure

    The CP-conserving two-Higgs-doublet model: the approach to the decoupling limit

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    A CP-even neutral Higgs boson with Standard-Model-like couplings may be the lightest scalar of a two-Higgs-doublet model. We study the decoupling limit of the most general CP-conserving two-Higgs-doublet model, where the mass of the lightest Higgs scalar is significantly smaller than the masses of the other Higgs bosons of the model. In this case, the properties of the lightest Higgs boson are nearly indistinguishable from those of the Standard Model Higgs boson. The first non-trivial corrections to Higgs couplings in the approach to the decoupling limit are also evaluated. The importance of detecting such deviations in precision Higgs measurements at future colliders is emphasized. We also clarify the case in which a neutral Higgs boson can possess Standard-Model-like couplings in a regime where the decoupling limit does not apply. The two-Higgs-doublet sector of the minimal supersymmetric model illustrates many of the above features.Comment: 54 pages, 2 tables, revtex4 format, some new material added (including elegant forms for the three-Higgs and four-Higgs couplings) and typographical errors fixe

    Difficult Scenarios for NMSSM Higgs Discovery at the LHC

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    We identify scenarios not ruled out by LEP data in which NMSSM Higgs detection at the LHC will be particularly challenging. We first review the `no-lose' theorem for Higgs discovery at the LHC that applies if Higgs bosons do not decay to other Higgs bosons - namely, with L=300 fb^-1, there is always one or more `standard' Higgs detection channel with at least a 5 sigma signal. However, we provide examples of no-Higgs-to-Higgs cases for which all the standard signals are no larger than 7 sigma implying that if the available L is smaller or the simulations performed by ATLAS and CMS turn out to be overly optimistic, all standard Higgs signals could fall below 5 sigma even in the no-Higgs-to-Higgs part of NMSSM parameter space. In the vast bulk of NMSSM parameter space, there will be Higgs-to-Higgs decays. We show that when such decays are present it is possible for all the standard detection channels to have very small significance. In most such cases, the only strongly produced Higgs boson is one with fairly SM-like couplings that decays to two lighter Higgs bosons (either a pair of the lightest CP-even Higgs bosons, or, in the largest part of parameter space, a pair of the lightest CP-odd Higgs bosons). A number of representative bench-mark scenarios of this type are delineated in detail and implications for Higgs discovery at various colliders are discussed.Comment: 31 pages, 5 figure

    Search Strategies for Non-Standard Higgs Bosons at Future e^+e^- Colliders

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    Already in the simplest two-Higgs-doublet model with CP violation in the Higgs sector, the 3√ó33\times3 mixing matrix for the neutral Higgs bosons can substantially modify their couplings, thereby endangering the ``classical'' Higgs search strategies. However, there are sum rules relating Yukawa and Higgs-Z couplings which ensure that the ZZ, b\anti b and t\anti t couplings of a given neutral 2HDM Higgs boson cannot all be simultaneously suppressed. This result implies that any single Higgs boson will be detectable at an e^+e^- collider if the Z+Higgs, b\anti b+Higgs {\it and} t\anti t+Higgs production channels are all kinematically accessible {\it and} if the integrated luminosity is sufficient. We explore, as a function of Higgs mass, the luminosity required to guarantee Higgs boson detection, and find that for moderate tan‚Ā°ő≤\tan\beta values the needed luminosity is unlikely to be available for all possible mixing scenarios. The additional difficulties for the case when the two-doublet Higgs sector is extended by adding one more singlet are summarized. Implications of the sum rules for Higgs discovery at the Tevatron and LHC are briefly discussed.Comment: 16 pages, 4 postscript figures, references added in replacemen
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