17,443 research outputs found
Some Novel Contributions to Radiative B Decay in Supersymmetry without R-parity
We present a systematic analysis at the leading log order of the influence of
combination of bilinear and trilinear R-parity violating couplings on the decay
b-->s gamma. Such contributions have never been explored in the context of this
decay. We show that influence of charged-slepton-Higgs mixing mediated loops
can dominate the SM and MSSM contributions and hence can provide strong bounds
on the combination of bilinear-trilinear R-parity violating couplings. Such
contributions are also enhanced by large tan beta. With substantially extended
basis of operators (28 operators), we provide illustrative analytical formulae
of the major contributions to complement our complete numerical results which
demonstrate the importance of QCD running effects.Comment: 4 pages, 2 figure
On Extended Electroweak Symmetries
We discuss extensions of the Standard Model through extending the electroweak
gauge symmetry. An extended electroweak symmetry requires a list of extra
fermionic and scalar states. The former is necessary to maintain cancellation
of gauge anomalies, and largely fixed by the symmetry embedding itself. The
latter is usually considered quite arbitrary, so long as a vacuum structure
admitting the symmetry breaking is allowed. Anomaly cancellation may be used to
link the three families of quarks and leptons together, given a perspective on
flavor physics. It is illustrated lately that the kind of models may also have
the so-called little Higgs mechanism incorporated. This more or less fixes the
scalar sector and take care of the hierarchy problem, making such models of
extended electroweak symmetries quite appealing candidates as TeV scale
effective field theories.Comment: 1+8 pages of latex with ws-procs9x6.cls; talk presented at Coral
Gables Conference 200
Little Higgs Model Completed with a Chiral Fermionic Sector
The implementation of the little Higgs mechanism to solve the hierarchy
problem provides an interesting guiding principle to build particle physics
models beyond the electroweak scale. Most model building works, however, pay
not much attention to the fermionic sector. Through a case example, we
illustrate how a complete and consistent fermionic sector of the TeV effective
field theory may actually be largely dictated by the gauge structure of the
model. The completed fermionic sector has specific flavor physics structure,
and many phenomenological constraints on the model can thus be obtained beyond
gauge, Higgs, and top physics. We take a first look on some of the quark sector
constraints.Comment: 14 revtex pages with no figure, largely a re-written version of
hep-ph/0307250 with elaboration on flavor sector FCNC constraints; accepted
for publication in Phys.Rev.
Characterisation of dispersions within annealed HVOLF thermally sprayed AlSnCu coatings
High velocity oxy-liquid fuel (HVOLF) AlSnCu coatings are characterised following annealing for up to 5 hours at 300°C. A combination of statistical analysis of BSE images and TEM observations demonstrate the decrease in the number of sub-micron and nanoscale Sn particles with annealing, commensurate with a decrease in the coating microhardness. TEM evidence further suggests the coarsening of nanoscale Sn through a mechanism of a liquid phase migration within the Al matrix. EELS and EFTEM additionally allow the identification of the precipitation of theta'
Unusual magnetoresistance in a topological insulator with a single ferromagnetic barrier
Tunneling surface current through a thin ferromagnetic barrier in a
three-dimensional topological insulator is shown to possess an extraordinary
response to the orientation of barrier magnetization. In contrast to
conventional magnetoresistance devices that are sensitive to the relative
alignment of two magnetic layers, a drastic change in the transmission current
is achieved by a single layer when its magnetization rotates by 90 degrees.
Numerical estimations predict a giant magnetoresistance as large as 800 % at
room temperature and the proximate exchange interaction of 40 meV in the
barrier. When coupled with electrical control of magnetization direction, this
phenomenon may be used to enhance the gating function with potentially sharp
turn-on/off for low power applications
Quark Loop Contributions to Neutron, Deuteron, and Mercury EDMs from Supersymmetry without R parity
We present a detailed analysis of the neutron, deuteron and mercury electric
dipole moment from supersymmetry without R parity, focusing on the quark-scalar
loop contributions. Being proportional to top Yukawa and top mass, such
contributions are often large. Analytical expressions illustrating the explicit
role of the R-parity violating parameters are given following perturbative
diagonalization of mass-squared matrices for the scalars. Dominant
contributions come from the combinations for which
we obtain robust bounds. It turns out that neutron and deuteron EDMs receive
much stronger contributions than mercury EDM and any null result at the future
deuteron EDM experiment or Los Alamos neutron EDM experiment can lead to
extra-ordinary constraints on RPV parameter space. Even if R-parity violating
couplings are real, CKM phase does induce RPV contribution and for some cases
such a contribution is as strong as contribution from phases in the R-parity
violating couplings.Hence, we have bounds directly on even if the RPV parameters are all real.
Interestingly, even if slepton mass and/or is as high as 1 TeV, it
still leads to neutron EDM that is an order of magnitude larger than the
sensitivity at Los Alamos experiment. Since the results are not much sensitive
to , our constraints will survive even if other observables tighten
the constraints on .Comment: 16 pages, 10 figures, accepted for publication in Physical Review
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