994 research outputs found
The Weak Mixing Angle From TeV Scale Quark-Lepton Unification
Unified theories based on an extended left-right symmetric group, , are constructed in five dimensions. The compactification scale
is assumed to be only a loop factor above the weak scale, so that the weak
mixing angle is predicted to be close to its tree level value of 0.239.
Boundary conditions in the 5th dimension break , removing powerful constraints from while allowing
a reliable calculation of the leading logarithm corrections to .
The compactification scale is expected in the 1--5 TeV region, depending on how
is broken. Two illustrative models are presented, and the
experimental signal of the gauge boson is discussed.Comment: 15 page
Realistic Anomaly Mediation with Bulk Gauge Fields
We present a simple general framework for realistic models of supersymmetry
breaking driven by anomaly mediation. We consider a 5-dimensional "brane
universe" where the visible and hidden sectors are localized on different
branes, and the standard model gauge bosons propagate in the bulk. In this
framework there can be charged scalar messengers that have contact interactions
with the hidden sector, either localized in the hidden sector or in the bulk.
These scalars obtain soft masses that feed into visible sector scalar masses at
two loop order via bulk gauge interactions. This contribution is automatically
flavor-blind, and can be naturally positive. If the messengers are in the bulk
this contribution is automatically the same order of magnitude as the anomaly
mediated contribution, independent of the brane spacing. If the messengers are
localized to a brane the two effects are of the same order for relatively small
brane spacings. The gaugino masses and A terms are determined completely by
anomaly mediation. In order for anomaly mediation to dominate over radion
mediation the radion must be is stabilized in a manner that preserves
supersymmetry, with supergravity effects included. We show that this occurs in
simple models. We also show that the mu problem can be solved by the vacuum
expectation value of a singlet in this framework.Comment: 16 pages, LaTeX2e, no figure
Symmetry Breaking Patterns for the Little Higgs from Strong Dynamics
We show how the symmetry breaking pattern of the simplest little Higgs model,
and that of the smallest moose model that incorporates an approximate custodial
SU(2), can be realized through the condensation of strongly coupled fermions.
In each case a custodial SU(2) symmetry of the new strong dynamics limits the
sizes of corrections to precision electroweak observables. In the case of the
simplest little Higgs, there are no new light states beyond those present in
the original model. However, our realization of the symmetry breaking pattern
of the moose model predicts an additional scalar field with mass of order a TeV
or higher that has exactly the same quantum numbers as the Standard Model Higgs
and which decays primarily to third generation quarks.Comment: 5 pages, 3 figure
Radion Mediated Supersymmetry Breaking
We point out that in supersymmetric theories with extra dimensions, radius
stabilization can give rise to a VEV for the component of the radius
modulus. This gives an important contribution to supersymmetry breaking of
fields that propagate in the bulk. A particularly attractive class of models is
obtained if the standard-model gauge fields propagate in the bulk, while the
quark and lepton fields are localized on a brane. This leads to gaugino
mediated supersymmetry breaking without the need for singlets in the hidden
sector. We analyze a simple explicit model in which this idea is realized
Unconventional fermions: The Price of Quark-Lepton Unification at TeV Scales
The early petite unification (PUT) of quarks and leptons at TeV scales with
sin^2 theta_W(M^2_Z) used as a constraint, necessitates the introduction of
extra quarks and leptons with unconventional electric charges (up to 4/3 for
the quarks and 2 for the leptons). This talk, in honor of Paul Frampton's 60th
birthday, will be devoted to the motivation and construction of models of early
unification and to their implications, including the issues of rare decays and
unconventional fermions.Comment: 10 pages, 2 figures. Talk in honor of Paul Frampton's 60th birthday
given at the Coral Gables Conference on Launching of Belle Epoque in High
Energy Physics and Cosmology, Ft. lauderdale, Florida, 17-21 December 2003.
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Fine Structure Constant Variation from a Late Phase Transition
Recent experimental data indicates that the fine structure constant alpha may
be varying on cosmological time scales. We consider the possibility that such a
variation could be induced by a second order phase transition which occurs at
late times (z ~ 1 - 3) and involves a change in the vacuum expectation value
(vev) of a scalar with milli-eV mass. Such light scalars are natural in
supersymmetric theories with low SUSY breaking scale. If the vev of this scalar
contributes to masses of electrically charged fields, the low-energy value of
alpha changes during the phase transition. The observational predictions of
this scenario include isotope-dependent deviations from Newtonian gravity at
sub-millimeter distances, and (if the phase transition is a sharp event on
cosmological time scales) the presence of a well-defined step-like feature in
the alpha(z) plot. The relation between the fractional changes in alpha and the
QCD confinement scale is highly model dependent, and even in grand unified
theories the change in alpha does not need to be accompanied by a large shift
in nucleon masses.Comment: 9 pages. V2: discussion on the energy density stored in the scalar
oscillations after the phase transition expanded. Typos corrected and Refs.
added. Version to appear in PL
Doublet-Triplet Splitting in Supersymmetric SU(6) by Missing VEV Mechanism
We present a realistic supersymmetric SU(6) model which implements
doublet-triplet splitting by the missing vev mechanism. The model makes use of
only the simplest representations, requires no fine tuning of parameters and
maintains coupling constant unification as a prediction. Fermion masses also
emerge in a very straightforward manner. This is the first time that the
missing vev mechanism has been realized in the context of SU(6).Comment: Revtex 4 pages; no figures; UMD-PP-99-01
Calculable Dynamical Supersymmetry Breaking on Deformed Moduli Spaces
We consider models of dynamical supersymmetry breaking in which the
extremization of a tree-level superpotential conflicts with a quantum
constraint. We show that in such models the low-energy effective theory near
the origin of moduli space is an O'Raifeartaigh model, and the sign of the
mass-squared for the pseudo-flat direction at the origin is calculable. We
analyze vector-like models with gauge groups SU(N) and Sp(2N) with and without
global symmetries. In all cases there is a stable minimum at the origin with an
unbroken U(1)_R symmetry.Comment: 8 pages, LaTeX2e, no figure
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