519 research outputs found
Bulk Gauge Fields in the Randall-Sundrum Model
We explore the consequences of placing the Standard Model gauge fields in the
bulk of the recently proposed localized gravity model of Randall and Sundrum.
We find that the Kaluza Klein excitations of these fields are necessarily
strongly coupled and we demonstrate that current precision electroweak data
constrain the lowest states to lie above TeV. Taking the weak scale
to be TeV, the resulting implications on the model parameters force
the bulk curvature, , to be larger than the higher dimensional Planck
scale, , violating the consistency of the theory. In turn, to preserve
|R_5|\lsim M^2, the weak scale must be pushed to \gsim 100 TeV. Hence we
conclude that it is disfavored to place the Standard Model gauge fields in the
bulk of this model as it is presently formulated.Comment: Improved results, 14 pages, Latex fil
Probing the Universal Randall-Sundrum Model at the ILC
The Randall-Sundrum model with all Standard Model (SM) fields in the bulk,
including the Higgs, can be probed by precision measurements at the ILC. In
particular, the couplings of the Higgs to the gauge bosons of the SM can be
determined with high accuracy at the ILC. Here we examine the deviations in
these couplings from their SM values within the framework of the Universal
Randall-Sundrum Model (URSM) as well as the corresponding couplings of the
first Higgs Kaluza-Klein excitation.Comment: 3 pages, 2 figs, contributed to the 2005 ALCPG and ILC Workshops,
Snowmass, CO, 8/14-8/27 2005; small typos remove
Warped Higgsless Models with IR--Brane Kinetic Terms
We examine a warped Higgsless model
in 5-- with IR(TeV)--brane kinetic terms. It is shown that adding a brane
term for the gauge field does not affect the scale (
TeV) where perturbative unitarity in is violated.
This term could, however, enhance the agreement of the model with the precision
electroweak data. In contrast, the inclusion of a kinetic term corresponding to
the custodial symmetry of the theory delays the unitarity violation
in scattering to energy scales of TeV for a significant
fraction of the parameter space. This is about a factor of 4 improvement
compared to the corresponding scale of unitarity violation in the Standard
Model without a Higgs. We also show that null searches for extra gauge bosons
at the Tevatron and for contact interactions at LEP II place non-trivial bounds
on the size of the IR-brane terms.Comment: 23 pages, 8 figure
Higgsless Electroweak Symmetry Breaking in Warped Backgrounds: Constraints and Signatures
We examine the phenomenology of a warped 5-dimensional model based on
SU(2) SU(2) U(1) model which implements
electroweak symmetry breaking through boundary conditions, without the presence
of a Higgs boson. We use precision electroweak data to constrain the general
parameter space of this model. Our analysis includes independent and
gauge couplings, radiatively induced UV boundary gauge kinetic terms, and all
higher order corrections from the curvature of the 5-d space. We show that this
setup can be brought into good agreement with the precision electroweak data
for typical values of the parameters. However, we find that the entire range of
model parameters leads to violation of perturbative unitarity in gauge boson
scattering and hence this model is not a reliable perturbative framework.
Assuming that unitarity can be restored in a modified version of this scenario,
we consider the collider signatures. It is found that new spin-1 states will be
observed at the LHC and measurement of their properties would identify this
model. However, the spin-2 graviton Kaluza-Klein resonances, which are a
hallmark of the Randall-Sundrum model, are too weakly coupled to be detected.Comment: More detailed analysis, added references, 43 pages, 15 figures, LaTe
Baryon Destruction by Asymmetric Dark Matter
We investigate new and unusual signals that arise in theories where dark
matter is asymmetric and carries a net antibaryon number, as may occur when the
dark matter abundance is linked to the baryon abundance. Antibaryonic dark
matter can cause {\it induced nucleon decay} by annihilating visible baryons
through inelastic scattering. These processes lead to an effective nucleon
lifetime of 10^{29}-10^{32} years in terrestrial nucleon decay experiments, if
baryon number transfer between visible and dark sectors arises through new
physics at the weak scale. The possibility of induced nucleon decay motivates a
novel approach for direct detection of cosmic dark matter in nucleon decay
experiments. Monojet searches (and related signatures) at hadron colliders also
provide a complementary probe of weak-scale dark-matter--induced baryon number
violation. Finally, we discuss the effects of baryon-destroying dark matter on
stellar systems and show that it can be consistent with existing observations.Comment: 26 pages, 6 figure
Constraints on Dimensional Warped Spaces
In order to investigate the phenomenological implications of allowing gauge
fields to propagate in warped spaces of more than five dimensions, we consider
a toy model of a space warped by the presence of a anisotropic bulk
cosmological constant. After solving the Einstein equation, three classes of
solutions are found, those in which the additional () dimensions are
growing, shrinking or remaining constant. It is found that gauge fields
propagating in these spaces have a significantly different Kaluza Klein (KK)
mass spectrum and couplings from that of the Randall and Sundrum model. This
leads to a greatly reduced lower bound on the KK scale, arising from
electroweak constraints, for spaces growing towards the IR brane.Comment: 6 pages, 5 figures PASCOS2010 International Symposium proceedin
Collider phenomenology of Higgs bosons in Left-Right symmetric Randall-Sundrum models
We investigate the collider phenomenology of a left-right symmetric
Randall-Sundrum model with fermions and gauge bosons in the bulk. We find that
the model is allowed by precision electroweak data as long as the ratio of the
(unwarped) Higgs vev to the curvature scale is . In that region
there can be substantial modifications to the Higgs properties. In particular,
the couplings to and are reduced, the coupling to gluons is enhanced,
and the coupling to can receive shifts in either direction. The
Higgs mass bound from LEP II data can potentially be relaxed to GeV.Comment: 21 pages, 11 figures. Minor changes to numerics; replaced with
published versio
Electroweak Constraints on Warped Geometry in Five Dimensions and Beyond
Here we consider the tree level corrections to electroweak (EW) observables
from standard model (SM) particles propagating in generic warped extra
dimensions. The scale of these corrections is found to be dominated by three
parameters, the Kaluza-Klein (KK) mass scale, the relative coupling of the KK
gauge fields to the Higgs and the relative coupling of the KK gauge fields to
fermion zero modes. It is found that 5D spaces that resolve the hierarchy
problem through warping typically have large gauge-Higgs coupling. It is also
found in where the additional dimensions are warped the relative
gauge-Higgs coupling scales as a function of the warp factor. If the warp
factor of the additional spaces is contracting towards the IR brane, both the
relative gauge-Higgs coupling and resulting EW corrections will be large.
Conversely EW constraints could be reduced by finding a space where the
additional dimension's warp factor is increasing towards the IR brane. We
demonstrate that the Klebanov Strassler solution belongs to the former of these
possibilities.Comment: 18 pages, 3 figures (references added) version to appear in JHE
Brane Localized Curvature for Warped Gravitons
We study the effects of including brane localized curvature terms in the
Randall-Sundrum (RS) model of the hierarchy. This leads to the existence of
brane localized kinetic terms for the graviton. Such terms can be induced by
brane and bulk quantum effects as well as Higgs-curvature mixing on the brane.
We derive the modified spectrum of Kaluza-Klein (KK) gravitons and their
couplings to 4-dimensional fields in the presence of these terms. We find that
the masses and couplings of the KK gravitons have considerable dependence on
the size of the brane localized terms; the weak-scale phenomenology of the
model is consequently modified . In particular, the weak-scale spin-2 graviton
resonances which generically appear in the RS model may be significantly
lighter than previously assumed. However, they may avoid detection as their
widths may be too narrow to be observable at colliders. In the contact
interaction limit, for a certain range of parameters, the experimental reach
for the scale of the theory is independent of the size of the boundary terms.Comment: 20 pages, 11 figures, LaTex, minor revision
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