1,371 research outputs found
Detecting and Studying in the MSSM: Implications of Supersymmetric Decays and Discriminating GUT Scenarios
We demonstrate that supersymmetric decays, as typified by the predictions of
several GUT-scale boundary condition choices, do not prevent detection of , at a TeV or collider operating
at anticipated luminosity. For much of parameter space the relative branching
ratios for various SUSY and non-SUSY decays can be measured with sufficient
accuracy that different GUT-scale boundary condition choices can be
distinguished from one another at a very high confidence level.Comment: 54 pages, full postscript file also available via anonymous ftp at
ftp://ucdhep.ucdavis.edu/gunion/pair.p
Effect of Multiple Higgs Fields on the Phase Structure of the SU(2)-Higgs Model
The SU(2)-Higgs model, with a single Higgs field in the fundamental
representation and a quartic self-interaction, has a Higgs region and a
confinement region which are analytically connected in the parameter space of
the theory; these regions thus represent a single phase. The effect of multiple
Higgs fields on this phase structure is examined via Monte Carlo lattice
simulations. For the case of N>=2 identical Higgs fields, there is no remaining
analytic connection between the Higgs and confinement regions, at least when
Lagrangian terms that directly couple different Higgs flavours are omitted. An
explanation of this result in terms of enhancement from overlapping phase
transitions is explored for N=2 by introducing an asymmetry in the hopping
parameters of the Higgs fields. It is found that an enhancement of the phase
transitions can still occur for a moderate (10%) asymmetry in the resulting
hopping parameters.Comment: 10 pages, 8 figures. References updated and minor typos correcte
Light Higgs bosons from a strongly interacting Higgs sector
The mass and the decay width of a Higgs boson in the minimal standard model
are evaluated by a variational method in the limit of strong self-coupling
interaction. The non-perturbative technique provides an interpolation scheme
between strong-coupling regime and weak-coupling limit where the standard
perturbative results are recovered. In the strong-coupling limit the physical
mass and the decay width of the Higgs boson are found to be very small as a
consequence of mass renormalization. Thus it is argued that the eventual
detection of a light Higgs boson would not rule out the existence of a strongly
interacting Higgs sector.Comment: 2 figure
Production of doubly charged scalars from the decay of singly charged scalars in the Higgs Triplet Model
The existence of doubly charged Higgs bosons (H^{\pm\pm}) is a distinctive
feature of the Higgs Triplet Model (HTM), in which neutrinos obtain tree-level
masses from the vacuum expectation value of a neutral scalar in a triplet
representation of SU(2)_L. We point out that a large branching ratio for the
decay of a singly charged Higgs boson to a doubly charged Higgs boson via
H^\pm\to H^{\pm\pm}W^* is possible in a sizeable parameter space of the HTM.
From the production mechanism q'qbar\to W^* \to H^{\pm\pm}H^\mp the above decay
mode would give rise to pair production of H^{\pm\pm}, with a cross section
which can be comparable to that of the standard pair-production mechanism
qqbar\to \gamma^*,Z^* \to H^{++}H^{--}. We suggest that the presence of a
sizeable branching ratio for H^\pm\to H^{\pm\pm}W^* could significantly enhance
the detection prospects of H^{\pm\pm} in the four-lepton channel. Moreover, the
decays H^0\to H^\pm W^* and A^0\to H^\pm W^* from production of the neutral
triplet scalars H^0 and A^0 would also provide an additional source of H^\pm,
which can subsequently decay to H^{\pm\pm}.Comment: 13 pages, 3 figures, two figures added in v2, to appear in Physical
Review
Production of pseudoscalar Higgs-bosons in collisions
We investigate the production of a pseudoscalar Higgs-boson using the
reaction at an collider with center of
mass energy of 500 GeV. Supersymmetric contributions are included and provide a
substantial enhancement to the cross section for most values of the symmetry
breaking parameters. We find that, despite the penalty incurred in converting
one of the beams into a source of backscattered photons, the
process is a promising channel for the detection of the .Comment: 9 pages RevTex + 2 Postscript figures tar.gzip.uuencode
Has HyperCP Observed a Light Higgs Boson?
The HyperCP collaboration has observed three events for the decay Sigma^+ ->
p mu^+ mu^- which may be interpreted as a new particle of mass 214.3 MeV.
However, existing data from kaon and B-meson decays severely constrain this
interpretation, and it is nontrivial to construct a model consistent with all
the data. In this letter we show that the ``HyperCP particle'' can be
identified with the light pseudoscalar Higgs boson in the next-to-minimal
supersymmetric standard model, the A_1^0. In this model there are regions of
parameter space where the A_1^0 can satisfy all the existing constraints from
kaon and B-meson decays and mediate Sigma^+ -> p mu^+ mu^- at a level
consistent with the HyperCP observation.Comment: 7 pages, 2 figure
Basis-independent methods for the two-Higgs-doublet model II. The significance of tan(beta)
In the most general two-Higgs-doublet model (2HDM), there is no distinction
between the two complex hypercharge-one SU(2) doublet scalar fields, Phi_a
(a=1,2). Thus, any two orthonormal linear combinations of these two fields can
serve as a basis for the Lagrangian. All physical observables of the model must
therefore be basis-independent. For example, tan(beta)=/ is
basis-dependent and thus cannot be a physical parameter of the model. In this
paper, we provide a basis-independent treatment of the Higgs sector with
particular attention to the neutral Higgs boson mass-eigenstates, which
generically are not eigenstates of CP. We then demonstrate that all physical
Higgs couplings are indeed independent of tan(beta). In specialized versions of
the 2HDM, tan(beta) can be promoted to a physical parameter of the
Higgs-fermion interactions. In the most general 2HDM, the Higgs-fermion
couplings can be expressed in terms of a number of physical "tan(beta)--like"
parameters that are manifestly basis-independent. The minimal supersymmetric
extension of the Standard Model provides a simple framework for exhibiting such
effects.Comment: 56 pages, 5 tables, with Eq. (65) corrected (erratum to appear in
Physical Review D
Single and Pair Production of Doubly Charged Higgs Bosons at Hadron Colliders
Current searches for doubly charged Higgs bosons (H^{\pm\pm}) at the Fermilab
Tevatron are sensitive to single production of H^{\pm\pm}, although the pair
production mechanism q\bar q\to H^{++}H^{--} is assumed to be dominant. In the
context of a Higgs Triplet Model we study the mechanism q'\bar q\to
H^{\pm\pm}H^{\mp} at the Tevatron and CERN Large Hadron Collider, and show that
its inclusion can significantly improve the search potential for H^{\pm\pm}.
Moreover, assuming that the neutrino mass is generated solely by the triplet
field Yukawa coupling to leptons, we compare the branching ratios of
H^{\pm\pm}\to l^\pm l^\pm and H^{\pm\pm}\to H^\pm W^* for the cases of a normal
hierarchical, inverted hierarchical and degenerate neutrino mass spectrum.Comment: 17 pages, 15 figures, references added, version to appear in PR
Global fit to Higgs signal strengths and couplings and implications for extended Higgs sectors
The most recent LHC data have provided a considerable improvement in the
precision with which various Higgs production and decay channels have been
measured. Using all available public results from ATLAS, CMS and the Tevatron,
we derive for each final state the combined confidence level contours for the
signal strengths in the (gluon fusion + ttH associated production) versus
(vector boson fusion + VH associated production) space. These "combined signal
strength ellipses" can be used in a simple, generic way to constrain a very
wide class of New Physics models in which the couplings of the Higgs boson
deviate from the Standard Model prediction. Here, we use them to constrain the
reduced couplings of the Higgs boson to up-quarks, down-quarks/leptons and
vector boson pairs. We also consider New Physics contributions to the
loop-induced gluon-gluon and photon-photon couplings of the Higgs, as well as
invisible/unseen decays. Finally, we apply our fits to some simple models with
an extended Higgs sector, in particular to Two-Higgs-Doublet models of Type I
and Type II, the Inert Doublet model, and the Georgi-Machacek triplet Higgs
model.Comment: 31 pages, 15 figures; v2: fixed important factor of 2 missing in Eq.
(1) (results unchanged), extended discussion in the next-to-last paragraph of
Section 3, some references added; v3: appendices and references added,
matches version accepted by PR
Two Higgs Bosons at the Tevatron and the LHC?
The best fit to the Tevatron results in the bb channel and the mild excesses
at CMS in the gamma-gamma channel at 136 GeV and in the tau-tau channel above
132 GeV can be explained by a second Higgs state in this mass range, in
addition to the one at 125 GeV recently discovered at the LHC. We show that a
scenario with two Higgs bosons at 125 GeV and 136 GeV can be consistent with
practically all available signal rates, including a reduced rate in the tau-tau
channel around 125 GeV as reported by CMS. An example in the parameter space of
the general NMSSM is given where, moreover, the signal rates of the 125 GeV
Higgs boson in the gamma-gamma channels are enhanced relative to the
expectation for a SM Higgs boson of this mass.Comment: 13 pages, 4 Table
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