227,465 research outputs found

### Alternatives to an Elementary Higgs

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

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

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

Already in the simplest two-Higgs-doublet model with CP violation in the
Higgs sector, the $3\times3$ 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 $\tan\beta$ 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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