64 research outputs found
Spectrum of TeV Particles in Warped Supersymmetric Grand Unification
In warped supersymmetric grand unification, XY gauge particles appear near
the TeV scale along with Kaluza-Klein towers of the standard model gauge
fields. In spite of this exotic low-energy physics, MSSM gauge coupling
unification is preserved and proton decay is naturally suppressed. In this
paper we study in detail the low-lying mass spectrum of superparticles and GUT
particles in this theory, taking supersymmetry breaking to be localized to the
TeV brane. The masses of the MSSM particles, Kaluza-Klein modes, and XY states
are all determined by two parameters, one which fixes the strength of the
supersymmetry breaking and the other which sets the scale of the infrared
brane. A particularly interesting result is that for relatively strong
supersymmetry breaking, the XY gauginos and the lowest Kaluza-Klein excitations
of the MSSM gauginos may both lie within reach of the LHC, providing the
possibility that the underlying unified gauge symmetry and the enhanced N=2
supersymmetry of the theory will both be revealed.Comment: 29 pages, 5 figure
Effective Field Theory and Unification in AdS Backgrounds
This work is an extension of our previous work, hep-th/0204160, which showed
how to systematically calculate the high energy evolution of gauge couplings in
compact AdS_5 backgrounds. We first directly compute the one-loop effects of
massive charged scalar fields on the low energy couplings of a gauge theory
propagating in the AdS background. It is found that scalar bulk mass scales
(which generically are of order the Planck scale) enter only logarithmically in
the corrections to the tree-level gauge couplings. As we pointed out
previously, we show that the large logarithms that appear in the AdS one-loop
calculation can be obtained within the confines of an effective field theory,
by running the Planck brane correlator from a high UV matching scale down to
the TeV scale. This result exactly reproduces our previous calculation, which
was based on AdS/CFT duality. We also calculate the effects of scalar fields
satisfying non-trivial boundary conditions (relevant for orbifold breaking of
bulk symmetries) on the running of gauge couplings.Comment: LaTeX, 27 pages; minor typos fixed, comments adde
Systematics of Coupling Flows in AdS Backgrounds
We give an effective field theory derivation, based on the running of Planck
brane gauge correlators, of the large logarithms that arise in the predictions
for low energy gauge couplings in compactified AdS}_5 backgrounds, including
the one-loop effects of bulk scalars, fermions, and gauge bosons. In contrast
to the case of charged scalars coupled to Abelian gauge fields that has been
considered previously in the literature, the one-loop corrections are not
dominated by a single 4D Kaluza-Klein mode. Nevertheless, in the case of gauge
field loops, the amplitudes can be reorganized into a leading logarithmic
contribution that is identical to the running in 4D non-Abelian gauge theory,
and a term which is not logarithmically enhanced and is analogous to a two-loop
effect in 4D. In a warped GUT model broken by the Higgs mechanism in the
bulk,we show that the matching scale that appears in the large logarithms
induced by the non-Abelian gauge fields is m_{XY}^2/k where m_{XY} is the bulk
mass of the XY bosons and k is the AdS curvature. This is in contrast to the UV
scale in the logarithmic contributions of scalars, which is simply the bulk
mass m. Our results are summarized in a set of simple rules that can be applied
to compute the leading logarithmic predictions for coupling constant relations
within a given warped GUT model. We present results for both bulk Higgs and
boundary breaking of the GUT gauge group.Comment: 22 pages, LaTeX, 3 figures. Comments and references adde
Gauge coupling renormalization in orbifold field theories
We investigate the gauge coupling renormalization in orbifold field theories
preserving 4-dimensional N=1 supersymmetry in the framework of 4-dimensional
effective supergravity. As a concrete example, we consider the 5-dimensional
Super-Yang-Mills theory on a slice of AdS_5. In our approach, one-loop gauge
couplings can be determined by the loop-induced axion couplings and the tree
level properties of 4-dimensional effective supergravity which are much easier
to be computed.Comment: 18 pages, JHEP style; 1-loop corrections to gauge kinetic functions
are fully computed, references are adde
Precision Electroweak Data and Unification of Couplings in Warped Extra Dimensions
Warped extra dimensions allow a novel way of solving the hierarchy problem,
with all fundamental mass parameters of the theory naturally of the order of
the Planck scale. The observable value of the Higgs vacuum expectation value is
red-shifted, due to the localization of the Higgs field in the extra dimension.
It has been recently observed that, when the gauge fields propagate in the
bulk, unification of the gauge couplings may be achieved. Moreover, the
propagation of fermions in the bulk allows for a simple solution to potentially
dangerous proton decay problems. However, bulk gauge fields and fermions pose a
phenomenological challenge, since they tend to induce large corrections to the
precision electroweak observables. In this article, we study in detail the
effect of gauge and fermion fields propagating in the bulk in the presence of
gauge brane kinetic terms compatible with gauge coupling unification, and we
present ways of obtaining a consistent description of experimental data, while
allowing values of the first Kaluza Klein mode masses of the order of a few
TeV.Comment: 32 pages, 7 figures. References adde
Spin and a Running Radius in RS1
We develop a renormalization group formalism for the compactified
Randall-Sundrum scenario wherein the extra-dimensional radius serves as the
scaling parameter. Couplings on the hidden brane scale as we move within local
effective field theories with varying size of the warped extra dimension. We
consider this RG approach applied to U(1) gauge theories and gravity. We use
this method to derive a low energy effective theory.Comment: 18 pages, minor changes, references adde
Opaque Branes in Warped Backgrounds
We examine localized kinetic terms for gauge fields which can propagate into
compact, warped extra dimensions. We show that these terms can have a relevant
impact on the values of the Kaluza-Klein (KK) gauge field masses, wave
functions, and couplings to brane and bulk matter. The resulting
phenomenological implications are discussed. In particular, we show that the
presence of opaque branes, with non-vanishing brane-localized gauge kinetic
terms, allow much lower values of the lightest KK mode than in the case of
transparent branes. Moreover, we show that if the large discrepancies among the
different determinations of the weak mixing angle would be solved in favor of
the value obtained from the lepton asymmetries, bulk electroweak gauge fields
in warped-extra dimensions may lead to an improvement of the agreement of the
fit to the electroweak precision data for a Higgs mass of the order of the weak
scale and a mass of the first gauge boson KK excitation most likely within
reach of the LHC.Comment: 37 pages, 12 figures, improved analysis of the precision electroweak
constraint
Family Unification on an Orbifold
We construct a family-unified model on a Z_2xZ_2 orbifold in five dimensions.
The model is based on a supersymmetric SU(7) gauge theory. The gauge group is
broken by orbifold boundary conditions to a product of grand unified SU(5) and
SU(2)xU(1) flavor symmetry. The structure of Yukawa matrices is generated by an
interplay between spontaneous breaking of flavor symmetry and geometric factors
arising due to field localization in the extra dimension.Comment: 13 page
Search for Radions at LEP2
A new scalar resonance, called the radion, with couplings to fermions and
bosons similar to those of the Higgs boson, is predicted in the framework of
Randall-Sundrum models, proposed solutions to the hierarchy problem with one
extra dimension. An important distinction between the radion and the Higgs
boson is that the radion would couple directly to gluon pairs, and in
particular its decay products would include a significant fraction of gluon
jets. The radion had the same quantum numbers as the Standard Model (SM) Higgs
boson, and therefore they can mix, with the resulting mass eigenstates having
properties different from those of the SM Higgs boson. Existing searches for
the Higgs boson are sensitive to the possible production and decay of radions
and Higgs bosons in these models. For the first time, searches for the SM Higgs
boson and flavour-independent and decay-mode independent searches for a neutral
Higgs boson are used in combination to explore the parameter space of the
Randall-Sundrum model. In the dataset recorded by the OPAL experiment at LEP,
no evidence for radion or Higgs particle production was observed in any of
those searches. The results are used to set limits on the radion and Higgs
boson masses.Comment: 18 pages, 6 figures, Submitted to Phys. Lett.
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