941 research outputs found
Scherk-Schwarz Supersymmetry Breaking for Quasi-localized Matter Fields and Supersymmetry Flavor Violation
We examine the soft supersymmetry breaking parameters induced by the
Scherk-Schwarz (SS) boundary condition in 5-dimensional orbifold field theory
in which the quark and lepton zero modes are quasi-localized at the orbifold
fixed points to generate the hierarchical Yukawa couplings. In such theories,
the radion corresponds to a flavon to generate the flavor hierarchy and at the
same time plays the role of the messenger of supersymmetry breaking. As a
consequence, the resulting soft scalar masses and trilinear -parameters of
matter zero modes at the compactification scale are highly flavor-dependent,
thereby can lead to dangerous flavor violations at low energy scales. We
analyze in detail the low energy flavor violations in SS-dominated
supersymmetry breaking scenario under the assumption that the compactification
scale is close to the grand unification scale and the 4-dimensional effective
theory below the compactification scale is given by the minimal supersymmetric
standard model. Our analysis can be applied to any supersymmetry breaking
mechanism giving a sizable -component of the radion superfield, e.g. the
hidden gaugino condensation model.Comment: revtex4, 22 pages, some numerical errors are corrected in
phenomenological analysis, main conclusion does not chang
Gauged Symmetries and Fayet-Iliopoulos Terms in 5D Orbifold Supergravity
We discuss a gauged supergravity on five-dimensional (5D) orbifold
() in which both a -even U(1) gauge field and the -odd
graviphoton take part in the gauging. Based on the off-shell
formulation of 5D supergravity, we analyze the structure of Fayet-Iliopoulos
(FI) terms allowed in such model. Introducing a -even gauge field
accompanies new bulk and boundary FI terms in addition to the known integrable
boundary FI term which could be present in the absence of any gauged
symmetry. Some physical consequences of these new FI terms are examined.Comment: 1+17 pages, 9 figures, typeset in JHEP styl
Scherk-Schwarz SUSY breaking from the viewpoint of 5D conformal supergravity
We reinterpret the Scherk-Schwarz (SS) boundary condition for SU(2)_R in a
compactified five-dimensional (5D) Poincare supergravity in terms of the
twisted SU(2)_U gauge fixing in 5D conformal supergravity. In such translation,
only the compensator hypermultiplet is relevant to the SS twist, and various
properties of the SS mechanism can be easily understood. Especially, we show
the correspondence between the SS twist and constant superpotentials within our
framework.Comment: 16 pages, no figur
Supersymmetry breaking in a warped slice with Majorana-type masses
We study the five-dimensional (5D) supergravity compactified on an orbifold
S^1/Z_2, where the U(1)_R symmetry is gauged by the graviphoton with Z_2-even
coupling. In contrast to the case of gauging with Z_2-odd coupling, this class
of models has Majorana-type masses and allows the Scherk-Schwarz (SS) twist
even in the warped spacetime. Starting from the off-shell formulation, we show
that the supersymmetry is always broken in an orbifold slice of AdS_5,
irrespective of the value of the SS twist parameter. We analyze the spectra of
gaugino and gravitino in such background, and find the SS twist can provide
sizable effects on them in the small warping region.Comment: 1+20 pages, 6 figure
Bulk Gauge Fields in Warped Space and Localized Supersymmetry Breaking
We consider five dimensional supersymmetric warped scenarios in which the
Standard Model quark and lepton fields are localized on the ultraviolet brane,
while the Standard Model gauge fields propagate in the bulk. Supersymmetry is
assumed to be broken on the infrared brane. The relative sizes of supersymmetry
breaking effects are found to depend on the hierarchy between the infrared
scale and the weak scale. If the infrared scale is much larger than the weak
scale the leading supersymmetry breaking effect on the visible brane is given
by gaugino mediation. The gaugino masses at the weak scale are proportional to
the square of the corresponding gauge coupling, while the dominant contribution
to the scalar masses arises from logarithmically enhanced radiative effects
involving the gaugino mass that are cutoff at the infrared scale. While the LSP
is the gravitino, the NLSP which is the stau is stable on collider time scales.
If however the infrared scale is close to the weak scale then the effects of
hard supersymmetry breaking operators on the scalar masses can become
comparable to those from gaugino mediation. These operators alter the relative
strengths of the couplings of gauge bosons and gauginos to matter, and give
loop contributions to the scalar masses that are also cutoff at the infrared
scale. The gaugino masses, while exhibiting a more complicated dependence on
the corresponding gauge coupling, remain hierarchical and become proportional
to the corresponding gauge coupling in the limit of strong supersymmetry
breaking. The scalar masses are finite and a loop factor smaller than the
gaugino masses. The LSP remains the gravitino.Comment: 36 pages, 2 figure
Dynamical symmetry breaking in Gauge-Higgs unification of 5D SUSY theory
We study the dynamical symmetry breaking in the gauge-Higgs unification of
the 5D SUSY theory, compactified on an orbifold, .
This theory identifies Wilson line degrees of freedoms as ``Higgs doublets''.
We consider and SU(6) models, in which the gauge
symmetries are reduced to and , respectively, through the
orbifolding boundary conditions. Quarks and leptons are bulk fields, so that
Yukawa interactions can be derived from the 5D gauge interactions. We estimate
the one loop effective potential of ``Higgs doublets'', and analyze the vacuum
structures in these two models. We find that the effects of bulk quarks and
leptons destabilize the suitable electro-weak vacuum. We show that the
introduction of suitable numbers of extra bulk fields possessing the suitable
representations can realize the appropriate electro-weak symmetry breaking.Comment: 15 pages, 4 figures;disscutions on Higgs quartic couplings adde
Hopping Conduction in Disordered Carbon Nanotubes
We report electrical transport measurements on individual disordered carbon
nanotubes, grown catalytically in a nanoporous anodic aluminum oxide template.
In both as-grown and annealed types of nanotubes, the low-field conductance
shows as exp[-(T_{0}/T)^{1/2}] dependence on temperature T, suggesting that
hopping conduction is the dominant transport mechanism, albeit with different
disorder-related coefficients T_{0}. The field dependence of low-temperature
conductance behaves an exp[-(xi_{0}/xi)^{1/2}] with high electric field xi at
sufficiently low T. Finally, both annealed and unannealed nanotubes exhibit
weak positive magnetoresistance at low T = 1.7 K. Comparison with theory
indicates that our data are best explained by Coulomb-gap variable range
hopping conduction and permits the extraction of disorder-dependent
localization length and dielectric constant.Comment: 10 pages, 5 figure
Angular Conditions,Relations between Breit and Light-Front Frames, and Subleading Power Corrections
We analyze the current matrix elements in the general collinear (Breit)
frames and find the relation between the ordinary (or canonical) helicity
amplitudes and the light-front helicity amplitudes. Using the conservation of
angular momentum, we derive a general angular condition which should be
satisfied by the light-front helicity amplitudes for any spin system. In
addition, we obtain the light-front parity and time-reversal relations for the
light-front helicity amplitudes. Applying these relations to the spin-1 form
factor analysis, we note that the general angular condition relating the five
helicity amplitudes is reduced to the usual angular condition relating the four
helicity amplitudes due to the light-front time-reversal condition. We make
some comments on the consequences of the angular condition for the analysis of
the high- deuteron electromagnetic form factors, and we further apply the
general angular condition to the electromagnetic transition between spin-1/2
and spin-3/2 systems and find a relation useful for the analysis of the
N- transition form factors. We also discuss the scaling law and the
subleading power corrections in the Breit and light-front frames.Comment: 24 pages,2 figure
Tau-Sleptons and Tau-Sneutrino in the MSSM with Complex Parameters
We present a phenomenological study of tau-sleptons stau_1,2 and
tau-sneutrino in the Minimal Supersymmetric Standard Model with complex
parameters A_tau, mu and M_1. We analyse production and decays of stau_1,2 and
tau-sneutrino at a future e^+ e^- collider. We present numerical predictions
for the important decay rates, paying particular attention to their dependence
on the complex parameters. The branching ratios of the fermionic decays of
stau_1 and tau-sneutrino show a significant phase dependence for tan(beta) <
10. For tan(beta) > 10 the branching ratios for the stau_2 decays into Higgs
bosons depend very sensitively on the phases. We show how information on the
phase phi(A_tau) and the other fundamental stau parameters can be obtained from
measurements of the stau masses, polarized cross sections and bosonic and
fermionic decay branching ratios, for small and large tan(beta) values. We
estimate the expected errors for these parameters. Given favorable conditions,
the error of A_tau is about 10% to 20%, while the errors of the remaining stau
parameters are in the range of approximately 1% to 3%. We also show that the
induced electric dipole moment of the tau-lepton is well below the current
experimental limit.Comment: LaTex, 25 pages, 11 figures (included); v2: extended discussion on
error determination, version to appear in Phys.Rev.
Radiative Scalar Meson Decays in the Light-Front Quark Model
We construct a relativistic wavefunction for scalar mesons within the
framework of light-front quark model(LFQM). This scalar wavefunction is used to
perform relativistic calculations of absolute widths for the radiative decay
processes, and
which incorporate the effects of glueball-
mixing. The mixed physical states are assumed to be ,and
for which the flavor-glue content is taken from the mixing
calculations of other works. Since experimental data for these processes are
poor, our results are compared with those of a recent non-relativistic model
calculation. We find that while the relativistic corrections introduced by the
LFQM reduce the magnitudes of the decay widths by 50-70%, the relative
strengths between different decay processes are fairly well preserved. We also
calculate decay widths for the processes and
(0^{++})\to\gamma\gamm involving the light scalars and
to test the simple model of these mesons. Our results of
model for these processes are not quite consistent with well-established data,
further supporting the idea that and are not conventional
states.Comment: 10 pages, 4 figure
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