288 research outputs found
Dynamical Electroweak Symmetry Breaking in SO(5)xU(1) Gauge-Higgs Unification with Top and Bottom Quarks
An SO(5)xU(1) gauge-Higgs unification model in the Randall-Sundrum warped
space with top and bottom quarks is constructed. Additional fermions on the
Planck brane make exotic particles heavy by effectively changing boundary
conditions of bulk fermions from those determined by orbifold conditions. Gauge
couplings of a top quark multiplet trigger electroweak symmetry breaking by the
Hosotani mechanism, simultaneously giving a top quark the observed mass. The
bottom quark mass is generated by combination of brane interactions and the
Hosotani mechanism, where only one ratio of brane masses is relevant when the
scale of brane masses is much larger than the Kaluza-Klein scale (\sim 1.5
TeV). The Higgs mass is predicted to be 49.9 (53.5) GeV for the warp factor
10^{15} (10^{17}). The Wilson line phase turns out \pi/2 and the Higgs
couplings to W and Z vanish so that the LEP2 bound for the Higgs mass is
evaded. In the flat spacetime limit the electroweak symmetry is unbroken.Comment: 35 pages, 2 figures. A few corrections are mad
Two loop finiteness of Higgs mass and potential in the gauge-Higgs unification
The zero mode of an extra-dimensional component of gauge potentials serves as
a 4D Higgs field in the gauge-Higgs unification. We examine QED on and determine the mass and potential of a 4D Higgs field (the
component) at the two loop level with gauge invariant reguralization. It is
seen that the mass is free from divergences and independent of the
renormalization scheme.Comment: 18 pages, 1 figur
Progress in weakly coupled string phenomenology
The weakly coupled vacuum of heterotic string theory remains
an attractive scenario for particle physics. The particle spectrum and the
issue of dilaton stabilization are reviewed. A specific model for hidden sector
condensation and supersymmetry breaking, that respects known constraints from
string theory, is described, and its phenomenological and cosmological
implications are discussed.Comment: 15 pages, full postscript also available from
http://phyweb.lbl.gov/theorygroup/papers/48640.p
Effects of Fermion Masses and Twisting on Non-Integrable Phases on Compact Extra Dimensions
The effective potential for the Wilson loop in the SU(2) gauge theory with
N_f massive fundamental and N_a massive adjoint fermions on S^1 x M^4 is
computed at the one-loop level, assuming periodic boundary conditions for the
gauge field and general boundary conditions for fermions. It is shown that
there are critical values for the bare mass, and the boundary condition
parameter for the adjoint fermions, beyond which the symmetry pattern changes.
However, neither bare mass, nor the boundary condition parameter for the
fundamental fermion play any role on the vacuum structure, thus the symmetry
breaking pattern. When the two different types of fermions with equal masses
exist together the pattern of the fundamental fermion dominate, and SU(2) gauge
symmetry remains intact independent of the fermion masses.Comment: 21 pages, 28 figures, version to appear in Nucl. Phys.
Gauge-Higgs Dark Matter
When the anti-periodic boundary condition is imposed for a bulk field in
extradimensional theories, independently of the background metric, the lightest
component in the anti-periodic field becomes stable and hence a good candidate
for the dark matter in the effective 4D theory due to the remaining accidental
discrete symmetry. Noting that in the gauge-Higgs unification scenario,
introduction of anti-periodic fermions is well-motivated by a phenomenological
reason, we investigate dark matter physics in the scenario. As an example, we
consider a five-dimensional SO(5)\timesU(1)_X gauge-Higgs unification model
compactified on the with the warped metric. Due to the structure of
the gauge-Higgs unification, interactions between the dark matter particle and
the Standard Model particles are largely controlled by the gauge symmetry, and
hence the model has a strong predictive power for the dark matter physics.
Evaluating the dark matter relic abundance, we identify a parameter region
consistent with the current observations. Furthermore, we calculate the elastic
scattering cross section between the dark matter particle and nucleon and find
that a part of the parameter region is already excluded by the current
experimental results for the direct dark matter search and most of the region
will be explored in future experiments.Comment: 16 pages, 2 figure
Effective theories of gauge-Higgs unification models in warped spacetime
We derive four-dimensional (4D) effective theories of the gauge-Higgs
unification models in the warped spacetime. The effective action can be
expressed in a simple form by neglecting subleading corrections to the wave
functions. We have shown in our previous works that some Higgs couplings to the
other fields are suppressed by factors that depend on from the
values in the standard model. Here is the Wilson line phase
along the fifth dimension, which characterizes the electroweak symmetry
breaking. The effective action derived here explicitly shows a nonlinear
structure of the Higgs sector, which clarifies the origins of those suppression
factors.Comment: 36 pages, 1 figur
A possible minimal gauge-Higgs unification
A possible minimal model of the gauge-Higgs unification based on the higher
dimensional spacetime M^4 X (S^1/Z_2) and the bulk gauge symmetry SU(3)_C X
SU(3)_W X U(1)_X is constructed in some details. We argue that the Weinberg
angle and the electromagnetic current can be correctly identified if one
introduces the extra U(1)_X above and a bulk scalar triplet. The VEV of this
scalar as well as the orbifold boundary conditions will break the bulk gauge
symmetry down to that of the standard model. A new neutral zero-mode gauge
boson Z' exists that gains mass via this VEV. We propose a simple fermion
content that is free from all the anomalies when the extra brane-localized
chiral fermions are taken into account as well. The issues on recovering a
standard model chiral-fermion spectrum with the masses and flavor mixing are
also discussed, where we need to introduce the two other brane scalars which
also contribute to the Z' mass in the similar way as the scalar triplet. The
neutrinos can get small masses via a type I seesaw mechanism. In this model,
the mass of the Z' boson and the compactification scale are very constrained as
respectively given in the ranges: 2.7 TeV < m_Z' < 13.6 TeV and 40 TeV < 1/R <
200 TeV.Comment: 20 pages, revised versio
An Attempt to Solve the Hierarchy Problem Based on Gravity-Gauge-Higgs Unification Scenario
We discuss a possible scenario to solve the hierarchy problem, in which
4-dimensional bosonic fields with all possible integer spins, graviton, gauge
boson and Higgs are unified in a framework of a gravity theory with extra
dimensions. The Higgs is identified with the extra space component of the
metric tensor. One-loop quantum effect on the Higgs mass-squared is explicitly
calculated in a five dimensional gravity theory compactified on . We
obtain a finite calculable Higgs mass-squared without suffering from quadratic
divergence, by virtue of general coordinate transformation invariance, which is
argued to be guaranteed by the summation over all Kaluza-Klein modes running in
the loop diagrams.Comment: 15pages, 2figures; version accepted for publication in Phys. Lett. B,
one reference adde
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