701 research outputs found
Linear Confinement for Mesons and Nucleons in AdS/QCD
By using a new parametrization of the dilaton field and including a cubic
term in the bulk scalar potential, we realize linear confinement in both meson
and nucleon sectors within the framework of soft-wall AdS/QCD. At the same time
this model also correctly incorporate chiral symmetry breaking. We compare our
resulting mass spectra with experimental data and find good agreement between
them.Comment: 14 pages, published version in JHE
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
An A4 flavor model for quarks and leptons in warped geometry
We propose a spontaneous A4 flavor symmetry breaking scheme implemented in a
warped extra dimensional setup to explain the observed pattern of quark and
lepton masses and mixings. The main advantages of this choice are the
explanation of fermion mass hierarchies by wave function overlaps, the
emergence of tribimaximal neutrino mixing and zero quark mixing at the leading
order and the absence of tree-level gauge mediated flavor violations. Quark
mixing is induced by the presence of bulk flavons, which allow for cross-brane
interactions and a cross-talk between the quark and neutrino sectors, realizing
the spontaneous symmetry breaking pattern A4 --> nothing first proposed in
[X.G.\,He, Y.Y.\,Keum, R.R.\,Volkas, JHEP{0604}, 039 (2006)]. We show that the
observed quark mixing pattern can be explained in a rather economical way,
including the CP violating phase, with leading order cross-interactions, while
the observed difference between the smallest CKM entries V_{ub} and V_{td} must
arise from higher order corrections. We briefly discuss bounds on the
Kaluza-Klein scale implied by flavor changing neutral current processes in our
model and show that the residual little CP problem is milder than in flavor
anarchic models.Comment: 34 pages, 2 figures; version published in JHE
See-saw neutrino masses and large mixing angles in the vortex background on a sphere
In the vortex background on a sphere, a single 6-dimensional fermion family
gives rise to 3 zero-modes in the 4-dimensional point of view, which may
explain the replication of families in the Standard Model. Previously, it had
been shown that realistic hierarchical mass and mixing patterns can be
reproduced for the quarks and the charged leptons. Here, we show that the
addition of a single heavy 6-dimensional field that is gauge singlet, unbound
to the vortex, and embedded with a bulk Majorana mass enables to generate 4D
Majorana masses for the light neutrinos through the see-saw mechanism. The
scheme is very predictive. The hierarchical structure of the fermion zero-modes
leads automatically to an inverted pseudo-Dirac mass pattern, and always
predicts one maximal angle in the neutrino see-saw matrix. It is possible to
obtain a second large mixing angle from either the charged lepton or the
neutrino sector, and we demonstrate that this model can fit all observed data
in neutrino oscillations experiments. Also, U_{e3} is found to be of the order
~0.1.Comment: 23 pages, 1 figur
Prospects for the development of odour baits to control the tsetse flies Glossina tachinoides and G. palpalis s.l.
Field studies were done of the responses of Glossina palpalis palpalis in CĂ´te d'Ivoire, and G. p. gambiensis and G. tachinoides in Burkina Faso, to odours from humans, cattle and pigs. Responses were measured either by baiting (1.) biconical traps or (2.) electrocuting black targets with natural host odours. The catch of G. tachinoides from traps was significantly enhanced (~5Ă—) by odour from cattle but not humans. In contrast, catches from electric targets showed inconsistent results. For G. p. gambiensis both human and cattle odour increased (>2Ă—) the trap catch significantly but not the catch from electric targets. For G. p. palpalis, odours from pigs and humans increased (~5Ă—) the numbers of tsetse attracted to the vicinity of the odour source but had little effect on landing or trap-entry. For G. tachinoides a blend of POCA (P = 3-n-propylphenol; O = 1-octen-3-ol; C = 4-methylphenol; A = acetone) alone or synthetic cattle odour (acetone, 1-octen-3-ol, 4-methylphenol and 3-n-propylphenol with carbon dioxide) consistently caught more tsetse than natural cattle odour. For G. p. gambiensis, POCA consistently increased catches from both traps and targets. For G. p. palpalis, doses of carbon dioxide similar to those produced by a host resulted in similar increases in attraction. Baiting traps with super-normal (~500 mg/h) doses of acetone also consistently produced significant but slight (~1.6Ă—) increases in catches of male flies. The results suggest that odour-baited traps and insecticide-treated targets could assist the AU-Pan African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC) in its current efforts to monitor and control Palpalis group tsetse in West Africa. For all three species, only ~50% of the flies attracted to the vicinity of the trap were actually caught by it, suggesting that better traps might be developed by an analysis of the visual responses and identification of any semiochemicals involved in short-range interaction
Reducing Constraints in a Higher Dimensional Extension of the Randall and Sundrum Model
In order to investigate the phenomenological implications of warped spaces in
more than five dimensions, we consider a dimensional extension to
the Randall and Sundrum model in which the space is warped with respect to a
single direction by the presence of an anisotropic bulk cosmological constant.
The Einstein equations are solved, giving rise to a range of possible spaces in
which the additional spaces are warped. Here we consider models in
which the gauge fields are free to propagate into such spaces. After carrying
out the Kaluza Klein (KK) decomposition of such fields it is found that the KK
mass spectrum changes significantly depending on how the additional
dimensions are warped. We proceed to compute the lower bound on the KK mass
scale from electroweak observables for models with a bulk
gauge symmetry and models with a bulk gauge
symmetry. It is found that in both cases the most favourable bounds are
approximately TeV, corresponding to a mass of the first gauge
boson excitation of about 4-6 TeV. Hence additional warped dimensions offer a
new way of reducing the constraints on the KK scale.Comment: 27 pages, 15 figures, v3: Additional comments in sections 1, 2 and 4.
New appendix added. Five additional figures. References adde
5D UED: Flat and Flavorless
5D UED is not automatically minimally flavor violating. This is due to flavor
asymmetric counter-terms required on the branes. Additionally, there are likely
to be higher dimensional operators which directly contribute to flavor
observables. We document a mostly unsuccessful attempt at utilizing
localization in a flat extra dimension to resolve these flavor constraints
while maintaining KK-parity as a good quantum number. It is unsuccessful
insofar as we seem to be forced to add brane operators in such a way as to
precisely mimic the effects of a double throat warped extra dimension. In the
course of our efforts, we encounter and present solutions to a problem common
to many extra dimensional models in which fields are "doubly localized:"
ultra-light modes. Under scrutiny, this issue seems tied to an intrinsic
tension between maintaining Kaluza-Klein parity and resolving mass hierarchies
via localization.Comment: 27 pages, 6 figure
Flavour in supersymmetry: horizontal symmetries or wave function renormalisation
We compare theoretical and experimental predictions of two main classes of
models addressing fermion mass hierarchies and flavour changing neutral
currents (FCNC) effects in supersymmetry: Froggatt-Nielsen (FN) U(1) gauged
flavour models and Nelson-Strassler/extra dimensional models with hierarchical
wave functions for the families. We show that whereas the two lead to identical
predictions in the fermion mass matrices, the second class generates a stronger
suppression of FCNC effects. We prove that, whereas at first sight the FN setup
is more constrained due to anomaly cancelation conditions, imposing unification
of gauge couplings in the second setup generates conditions which precisely
match the mixed anomaly constraints in the FN setup. Finally, we provide an
economical extra dimensional realisation of the hierarchical wave functions
scenario in which the leptonic FCNC can be efficiently suppressed due to the
strong coupling (CFT) origin of the electron mass.Comment: 23 page
CP violation Beyond the MSSM: Baryogenesis and Electric Dipole Moments
We study electroweak baryogenesis and electric dipole moments in the presence
of the two leading-order, non-renormalizable operators in the Higgs sector of
the MSSM. Significant qualitative and quantitative differences from MSSM
baryogenesis arise due to the presence of new CP-violating phases and to the
relaxation of constraints on the supersymmetric spectrum (in particular, both
stops can be light). We find: (1) spontaneous baryogenesis, driven by a change
in the phase of the Higgs vevs across the bubble wall, becomes possible; (2)
the top and stop CP-violating sources can become effective; (3) baryogenesis is
viable in larger parts of parameter space, alleviating the well-known
fine-tuning associated with MSSM baryogenesis. Nevertheless, electric dipole
moments should be measured if experimental sensitivities are improved by about
one order of magnitude.Comment: 33 pages, 6 figure
Two-loop Corrections to the B to pi Form Factor from QCD Sum Rules on the Light-Cone and |V(ub)|
We calculate the leading-twist O(alphas^2 beta0) corrections to the B to pi
transition form factor f+(0) in light-cone sum rules. We find that, as
expected, there is a cancellation between the O(alphas^2 beta0) corrections to
fB f+(0) and the large corresponding corrections to fB, calculated in QCD sum
rules. This suggests the insensitivity of the form factors calculated in the
light-cone sum rules approach to this source of radiative corrections. We
further obtain an improved determination of the CKM matrix element |V(ub)|,
using latest results from BaBar and Belle for f+(0)|V(ub)|.Comment: 18 pages, 3 figure
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