7,793 research outputs found
Proposal for Higgs and Superpartner Searches at the LHCb Experiment
The spectrum of supersymmetric theories with R-parity violation are much more
weakly constrained than that of supersymmetric theories with a stable
neutralino. We investigate the signatures of supersymmetry at the LHCb
experiment in the region of parameter space where the neutralino decay leaves a
displaced vertex. We find sensitivity to squark production up to squark masses
of order 1 TeV. We note that if the Higgs decays to neutralinos in this
scenario, LHCb should see the lightest Higgs boson before ATLAS and CMS.Comment: 7 pages, 5 figure
A Perturbative Calculation of the Electromagnetic Form Factors of the Deuteron
Making use of the effective field theory expansion recently developed by the
authors, we compute the electromagnetic form factors of the deuteron
analytically to next-to-leading order (NLO). The computation is rather simple,
and involves calculating several Feynman diagrams, using dimensional
regularization. The results agree well with data and indicate that the
expansion is converging. They do not suffer from any ambiguities arising from
off-shell versus on-shell amplitudes.Comment: 22 pages, 8 figures. Discussion of effective range theory added,
typos correcte
Optical Nonlinearities at the Interface between Glass and Liquid Crystal
In this paper, the optical behavior of a nonlinear interface is studied. The nonlinear medium has been a nematic liquid crystal, namely MBBA, and the nonlinear one, glasses of different types (F-10 and F-2) depending on the experimental needs. The anchoring forces at the boundary have been found to inhibit the action of the evanescent field in the case of total internal reflection. Most of observed nonlinearities are due to thermal effects. As a consequence, liquid crystals do not seem to be good candidates for total internal reflection optical bistability
Minimal Gaugino Mediation
We propose Minimal Gaugino Mediation as the simplest known solution to the
supersymmetric flavor and CP problems. The framework predicts a very minimal
structure for the soft parameters at ultra-high energies: gaugino masses are
unified and non-vanishing whereas all other soft supersymmetry breaking
parameters vanish. We show that this boundary condition naturally arises from a
small extra dimension and present a complete model which includes a new
extra-dimensional solution to the mu problem. We briefly discuss the predicted
superpartner spectrum as a function of the two parameters of the model. The
commonly ignored renormalization group evolution above the GUT scale is crucial
to the viability of Minimal Gaugino Mediation but does not introduce new model
dependence.Comment: LaTeX, 16 pages, 4 figures, running of the bottom and tau Yukawas
included, plots revise
The Simplest Little Higgs
We show that the SU(3) little Higgs model has a region of parameter space in
which electroweak symmetry breaking is natural and in which corrections to
precision electroweak observables are sufficiently small. The model is anomaly
free, generates a Higgs mass near 150 GeV, and predicts new gauge bosons and
fermions at 1 TeV.Comment: 13 pages + appendix, typos corrected, version to appear in JHE
Chandra Phase-Resolved X-ray Spectroscopy of the Crab Pulsar II
We present a new study of the X-ray spectral properties of the Crab Pulsar.
The superb angular resolution of the Chandra X-ray Observatory enables
distinguishing the pulsar from the surrounding nebulosity. Analysis of the
spectrum as a function of pulse phase allows the least-biased measure of
interstellar X-ray extinction due primarily to photoelectric absorption and
secondarily to scattering by dust grains in the direction of the Crab Nebula.
We modify previous findings that the line-of-sight to the Crab is
under-abundant in oxygen and provide measurements with improved accuracy and
less bias. Using the abundances and cross sections from Wilms, Allen & McCray
(2000) we find [O/H] = ( is
solar abundance). We also measure for the first time the impact of scattering
of flux out of the image by interstellar grains. We find . Analysis of the spectrum as a function of pulse phase also
measures the X-ray spectral index even at pulse minimum --- albeit with
increasing statistical uncertainty. The spectral variations are, by and large,
consistent with a sinusoidal variation. The only significant variation from the
sinusoid occurs over the same phase range as some rather abrupt behavior in the
optical polarization magnitude and position angle. We compare these spectral
variations to those observed in Gamma-rays and conclude that our measurements
are both a challenge and a guide to future modeling and will thus eventually
help us understand pair cascade processes in pulsar magnetospheres. The data
were also used to set new, and less biased, upper limits to the surface
temperature of the neutron star for different models of the neutron star
atmosphere.Comment: 32 pages, 6 figures submitted to the Astrophysical journa
Supersymmetric Model of Muon Anomalous Magnetic Moment and Neutrino Masses
We propose the novel lepton-number relationship , which
is uniquely realized by the interaction in supersymmetry and may account for a possibly large
muon anomalous magnetic moment. Neutrino masses (with bimaximal mixing) may be
generated from the spontaneous and soft breaking of this lepton symmetry.Comment: 10 pages, including 2 figure
Supersymmetry Breaking through Transparent Extra Dimensions
We propose a new framework for mediating supersymmetry breaking through an
extra dimension. It predicts positive scalar masses and solves the
supersymmetric flavor problem. Supersymmetry breaks on a ``source'' brane that
is spatially separated from a parallel brane on which the standard model matter
fields and their superpartners live. The gauge and gaugino fields propagate in
the bulk, the latter receiving a supersymmetry breaking mass from direct
couplings to the source brane. Scalar masses are suppressed at the high scale
but are generated via the renormalization group. We briefly discuss the
spectrum and collider signals for a range of compactification scales.Comment: 20 page
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