10,401 research outputs found
Neutralinos in E_6 inspired supersymmetric U(1)' models
The neutralino sector in E_6 inspired supersymmetric models with extra
neutral gauge bosons and singlet Higgs fields contains additional gaugino and
singlino states compared to the MSSM. We discuss the neutralino mixing in rank
5 and rank 6 models and analyze the supersymmetric parameter space where the
light neutralinos have mainly singlino or MSSM character. The neutralino
character, resonance effects of the new gauge bosons and, assuming mSUGRA-type
RGEs, different selectron masses lead to significant differences between the
MSSM and the extended models in neutralino production at an e^+e^- linear
collider. Beam polarization may improve the signatures to distinguish between
the models. In an appendix, we present the mass terms of the gauge bosons,
charginos and sfermions which show a significant different mass spectrum than
in the MSSM and give all relevant neutralino couplings.Comment: 26 pages, LaTeX, 5 eps figures; version to be published in EPJ
Neutralino Production with Polarized Beams in Extended Supersymmetric Models
We discuss associated neutralino production e^+ e^- --> \tilde{\chi}^0_1
\tilde{\chi}^0_2 with both beams polarized in the MSSM, NMSSM and an E_6 model.
It is shown that neutralinos with a large singlino component can be produced at
a high luminosity linear collider in a broad parameter range. Polarization
effects in the extended models are compared over the whole parameter space
where the lightest neutralino is mainly a singlino. We explain the complete
different behavior of these models in some parameter regions, which may help to
identify the respective supersymmetric model.Comment: 10 pages, LaTeX, 10 eps figures, contribution to the Proceedings of
the "2nd Joint ECFA/DESY Study on Physics and Detectors for a Linear
Electron-Positron Collider
Chargino Production and Decay in Photon-Photon-Collisions
We discuss the pair production of charginos in collisions of polarized
photons , () and the
subsequent leptonic decay of the lighter chargino including the complete spin correlations.
Analytical formulae are given for the polarization and the spin-spin
correlations of the charginos. Since the production is a pure QED process the
decay dynamics can be studied separately. For high energy photons from Compton
backscattering of polarized laser pulses off polarized electron beams numerical
results are presented for the cross section, the angular distribution and the
forward-backward asymmetry of the decay positron. Finally we study the
dependence on the gaugino mass parameter and on the sneutrino mass for a
gaugino-like MSSM scenario.Comment: 22 pages, 15 figures, version to be published in Eur. Phys. J.
Assessing the ability of the 14C projection-age method to constrain the circulation of the past in a 3-D ocean model
Radiocarbon differences between benthic and planktonic foraminifera (B-P ages) and radiocarbon projection ages are both used to determine changes of the past ocean circulation rate. A global 3-D ocean circulation model with a constant modern ocean circulation is used to study which method is less influenced by atmospheric Î14C variations. Three factors cause uncertainties: first, the long equilibration time of the ocean after atmospheric Î14C changes; second, different mixing processes in the ocean, which cause an ocean response of smaller amplitude than the atmospheric forcing; and third, the unknown source region and corresponding initial surface 14C reservoir age of subsurface waters. The model suggests that B-P ages and projection ages have lower uncertainties the closer they are to deepwater formation zones. In the North Atlantic the B-P age method is less influenced by atmospheric Î14C variations than the projection-age method. Projections ages vary less in the Pacific as long as atmospheric Î14C decreases linearly. A more irregular atmospheric Î14C evolution leads to age variations of similar magnitude with both methods. On the basis of the model experiment, we suggest a potential improvement of the projection-age method
Identifying the NMSSM by the interplay of LHC and ILC
The interplay between the LHC and the International Linear Collider
(ILC) with GeV might be crucial for the discrimination between
the minimal and next-to-minimal supersymmetric standard model. We present an
NMSSM scenario, where the light neutralinos have a significant singlino
component, that cannot be distinguished from the MSSM by cross sections and
mass measurements. Mass and mixing state predictions for the heavier
neutralinos from the ILC analysis at different energy stages and comparison
with observation at the LHC, lead to clear identification of the particle
character and identify the underlying supersymmetric model.Comment: 8 pages, 2 eps figures, revtex4 style Contribution to the `2005
International Linear Collider Workshop - Stanford, U.S.A.
Multi-field modelling and simulation of large deformation ductile fracture
In the present contribution we focus on a phase-ïŹeld approach to ductile fracture applied to large deformation contact problems. Phase-ïŹeld approaches to fracture allow for an eïŹcient numerical investigation of complex three-dimensional fracture problems, as they arise in contact and impact situations. To account for large deformations the underlying formulation is based on a multiplicative decomposition of the deformation gradient into an elastic and plastic part. Moreover, we make use of a fourth-order crack regularization combined with gradient plasticity. Eventually, a demonstrative example shows the capability of the proposed framework
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