1,060 research outputs found
New Production Mechanism of Neutral Higgs Bosons with Right scalar tau neutrino as the LSP
Motived by the neutrino oscillation data, we consider the lightest tau
sneutrino (which is mostly the right tau sneutrino) to be
the lightest supersymmetric particle (LSP) in the framework of the minimal
supersymmetric Standard Model. Both the standard and the non-standard trilinear
scalar coupling terms are included for the right tau sneutrino interactions.
The decay branching ratio of
can become so large that the production rate of the lightest neutral Higgs
boson () can be largely enhanced at electron or hadron colliders, either
from the direct production of or from the decay of
charginos, neutralinos, sleptons, and the cascade decay of squarks and gluinos,
etc. Furthermore, because of the small LSP annihilation rate, can be a good candidate for cold dark matter.Comment: 11 pages, RevTex, 3 eps figures. We clarify the theoretical framework
of this study, with a note added in the end, and correct an equation, with
updated figure
Recommended from our members
Microscopic insight into the bilateral formation of carbon spirals from a symmetric iron core
Mirrored carbon-spirals have been produced from pressured ferrocene via the bilateral extrusion of the spiral pairs from an iron core. A parametric plot of the surface geometry displays the fractal growth of the conical helix made with the logarithmic spiral. Electron microscopy studies show the core is a crystalline cementite which grows and transforms its shape from spherical to biconical as it extrudes two spiralling carbon arms. In a cross section along the arms we observe graphitic flakes arranged in a herringbone structure, normal to which defects propagate. Local-wave-pattern analysis reveals nanoscale defect patterns of two-fold symmetry around the core. The data suggest that the bilateral growth originates from a globular cementite crystal with molten surfaces and the nano-defects shape emerging hexagonal carbon into a fractal structure. Understanding and knowledge obtained provide a basis for the controlled production of advanced carbon materials with designed geometries
Gauge Unification in Higher Dimensions
A complete 5-dimensional SU(5) unified theory is constructed which, on
compactification on the orbifold with two different Z_2's (Z_2 and Z_2'),
yields the minimal supersymmetric standard model. The orbifold accomplishes
SU(5) gauge symmetry breaking, doublet-triplet splitting, and a vanishing of
proton decay from operators of dimension 5. Until 4d supersymmetry is broken,
all proton decay from dimension 4 and dimension 5 operators is forced to vanish
by an exact U(1)_R symmetry. Quarks and leptons and their Yukawa interactions
are located at the Z_2 orbifold fixed points, where SU(5) is unbroken. A new
mechanism for introducing SU(5) breaking into the quark and lepton masses is
introduced, which originates from the SU(5) violation in the zero-mode
structure of bulk multiplets. Even though SU(5) is absent at the Z_2' orbifold
fixed point, the brane threshold corrections to gauge coupling unification are
argued to be negligibly small, while the logarithmic corrections are small and
in a direction which improves the agreement with the experimental measurements
of the gauge couplings. Furthermore, the X gauge boson mass is lowered, so that
proton decay to e^+ \pi^0 is expected with a rate within about one order of
magnitude of the current limit. Supersymmetry breaking occurs on the Z_2'
orbifold fixed point, and is felt directly by the gauge and Higgs sectors,
while squarks and sleptons acquire mass via gaugino mediation, solving the
supersymmetric flavor problem.Comment: 21 pages, Latex, references added, final versio
Nanoelectromechanical coupling in fullerene peapods probed via resonant electrical transport experiments
Fullerene peapods, that is carbon nanotubes encapsulating fullerene
molecules, can offer enhanced functionality with respect to empty nanotubes.
However, the present incomplete understanding of how a nanotube is affected by
entrapped fullerenes is an obstacle for peapods to reach their full potential
in nanoscale electronic applications. Here, we investigate the effect of C60
fullerenes on electron transport via peapod quantum dots. Compared to empty
nanotubes, we find an abnormal temperature dependence of Coulomb blockade
oscillations, indicating the presence of a nanoelectromechanical coupling
between electronic states of the nanotube and mechanical vibrations of the
fullerenes. This provides a method to detect the C60 presence and to probe the
interplay between electrical and mechanical excitations in peapods, which thus
emerge as a new class of nanoelectromechanical systems.Comment: 7 pages, 3 figures. Published in Nature Communications. Free online
access to the published version until Sept 30th, 2010, see
http://www.nature.com/ncomms/journal/v1/n4/abs/ncomms1034.htm
Towards precision medicine for hypertension: a review of genomic, epigenomic, and microbiomic effects on blood pressure in experimental rat models and humans
Compelling evidence for the inherited nature of essential hypertension has led to extensive research in rats and humans. Rats have served as the primary model for research on the genetics of hypertension resulting in identification of genomic regions that are causally associated with hypertension. In more recent times, genome-wide studies in humans have also begun to improve our understanding of the inheritance of polygenic forms of hypertension. Based on the chronological progression of research into the genetics of hypertension as the "structural backbone," this review catalogs and discusses the rat and human genetic elements mapped and implicated in blood pressure regulation. Furthermore, the knowledge gained from these genetic studies that provide evidence to suggest that much of the genetic influence on hypertension residing within noncoding elements of our DNA and operating through pervasive epistasis or gene-gene interactions is highlighted. Lastly, perspectives on current thinking that the more complex "triad" of the genome, epigenome, and the microbiome operating to influence the inheritance of hypertension, is documented. Overall, the collective knowledge gained from rats and humans is disappointing in the sense that major hypertension-causing genes as targets for clinical management of essential hypertension may not be a clinical reality. On the other hand, the realization that the polygenic nature of hypertension prevents any single locus from being a relevant clinical target for all humans directs future studies on the genetics of hypertension towards an individualized genomic approach
Detailed Analysis of Proton Decay Rate in the Minimal Supersymmetric SO(10) Model
We consider the minimal supersymmetric SO(10) model, where only one {\bf 10}
and one Higgs multiplets have Yukawa couplings with matter
multiplets. This model has the high predictive power for the Yukawa coupling
matrices consistent with the experimental data of the charged fermion mass
matrices, and all the Yukawa coupling matrices are completely determined once a
few parameters in the model are fixed. This feature is essential for definite
predictions to the proton decay rate through the dimension five operators. We
analyze the proton decay rate for the dominant decay modes by including as many free parameters as possible and varying them.
There are two free parameters in the Yukawa sector, while five in the Higgsino
sector. It is found that an allowed region exists when the free parameters in
the Higgs sector are tuned so as to cancel the proton decay amplitude. The
resultant proton lifetime is proportional to and the allowed
region eventually disappears as becomes large.Comment: 15 pages, 3 figures; the version to appear in JHE
Cornering Solar Radiative-Zone Fluctuations with KamLAND and SNO Salt
We update the best constraints on fluctuations in the solar medium deep
within the solar Radiative Zone to include the new SNO-salt solar neutrino
measurements. We find that these new measurements are now sufficiently precise
that neutrino oscillation parameters can be inferred independently of any
assumptions about fluctuation properties. Constraints on fluctuations are also
improved, with amplitudes of 5% now excluded at the 99% confidence level for
correlation lengths in the range of several hundred km. Because they are
sensitive to correlation lengths which are so short, these solar neutrino
results are complementary to constraints coming from helioseismology.Comment: 4 pages, LaTeX file using RevTEX4, 6 figures include
SU(5) monopoles and non-abelian black holes
We construct spherically and axially symmetric monopoles in SU(5)
Yang-Mills-Higgs theory both in flat and curved space as well as spherical and
axial non-abelian, ''hairy'' black holes. We find that in analogy to the SU(2)
case, the flat space monopoles are either non-interacting (in the BPS limit) or
repelling. In curved space, however, gravity is able to overcome the repulsion
for suitable choices of the Higgs coupling constants and the gravitational
coupling. In addition, we confirm that indeed all qualitative features of
(gravitating) SU(2) monopoles are found as well in the SU(5) case. For the
non-abelian black holes, we compare the behaviour of the solutions in the BPS
limit with that for non-vanishing Higgs self-coupling constants.Comment: 14 Revtex pages, 9 PS-figure
Strongly Coupled Grand Unification in Higher Dimensions
We consider the scenario where all the couplings in the theory are strong at
the cut-off scale, in the context of higher dimensional grand unified field
theories where the unified gauge symmetry is broken by an orbifold
compactification. In this scenario, the non-calculable correction to gauge
unification from unknown ultraviolet physics is naturally suppressed by the
large volume of the extra dimension, and the threshold correction is dominated
by a calculable contribution from Kaluza-Klein towers that gives the values for
\sin^2\theta_w and \alpha_s in good agreement with low-energy data. The
threshold correction is reliably estimated despite the fact that the theory is
strongly coupled at the cut-off scale. A realistic 5d supersymmetric SU(5)
model is presented as an example, where rapid d=6 proton decay is avoided by
putting the first generation matter in the 5d bulk.Comment: 17 pages, latex, to appear in Phys. Rev.
- …