166 research outputs found
CP asymmetries in chargino production and decay: the three-body decay case
We study CP violation in chargino production and decay in the Minimal
Supersymmetric Standard Model (MSSM) with complex parameters at an e^+ e^-
linear collider with longitudinally polarized beams. We investigate
CP-sensitive asymmetries by means of triple product correlations and study
their dependence on the complex parameters M_1 and mu. We give numerical
predictions for the asymmetries and their measurability at the future
International Linear Collider. Our results show that the CP asymmetries can be
measured in a large region of the MSSM parameter space.Comment: 22 pages, LaTeX, 8 figures; v2: structural changes and references
added, main conclusions unchanged, published versio
Effects of Lepton Flavour Violation on Chargino Production at the Linear Collider
We study the effects of lepton flavour violation (LFV) on the production
processes e+e- --> \chi+_i \chi-_j at a linear collider with longitudinal e+
and e- beam polarizations. In the case of LFV the sneutrino mass eigenstates
have no definite flavour, therefore, in the t-channel more than one sneutrino
mass eigenstate can contribute to the chargino production cross sections. Our
framework is the Minimal Supersymmetric Standard Model (MSSM) including LFV
terms. We show that in spite of the restrictions on the LFV parameters due to
the current limits on rare lepton decays, the cross section \sigma(e+e- -->
\chi+_1 \chi-_1) can change by a factor of 2 or more when varying the LFV
mixing angles. We point out that even if the present bound on BR(tau- --> e-
gamma) improves by a factor of thousand the influence of LFV on the chargino
production cross section can be significant. These results could have an
important impact on the strategies for determining the underlying model
parameters at the linear collider.Comment: 11pp; final version for JHE
SPD deformation of pearlitic, bainitic and martensitic steels
The deformation behavior of nearly fully pearlitic, bainitic and martensitic
steels during severe plastic deformation is summarized in this paper. Despite
their significantly different yield stresses and their microstructures, their
hardening behavior during SPD is similar. Due to the enormous hardening
capacity the SPD deformation is limited by the strength of the tool materials.
The microstructure at the obtainable limit of strain are quite similar, which
is a nanocrystalline structure in the order of 10 nm, dependent on the
obtainable strain. The nanograins are partially supersaturated with carbon and
the grain boundaries are stabilized by carbon. Another characteristic feature
is the anisotropy in grain shape which results in an anisotropy of strength,
ductility and fracture toughness. The results are important for the development
of ultra-strong materials and essential for this type of steels which are
frequently used for application where the behavior under rolling contact and
sliding contact is important
Impact of squark generation mixing on the search for gluinos at LHC
We study gluino decays in the Minimal Supersymmetric Standard Model (MSSM)
with squark generation mixing. We show that the effect of this mixing on the
gluino decay branching ratios can be very large in a significant part of the
MSSM parameter space despite the very strong experimental constraints on quark
flavour violation (QFV) from B meson observables. Especially we find that under
favourable conditions the branching ratio of the the QFV gluino decay gluino ->
c bar{t} (bar{c} t) + neutralino_1 can be as large as about 50%. We also find
that the squark generation mixing can result in a multiple-edge (3- or 4-edge)
structure in the charm-top quark invariant mass distribution. The appearance of
this remarkable structure provides an additional powerful test of
supersymmetric QFV at LHC. These could have an important impact on the search
for gluinos and the determination of the MSSM parameters at LHC.Comment: 22 pages, 10 figures, close to the published versio
CP asymmetries in scalar bottom quark decays
We propose CP asymmetries based on triple product correlations in the decays
sbottom_m -> top chargino_j with subsequent decays of top and chargino_j. For
the subsequent chargino_j decay into a leptonic final state l^- \nu
neutralino_1 we consider the three possible decay chains chargino_j -> l^-
sneutrino -> l^- \nu neutralino_1, chargino_j -> slepton_n \nu -> l^- \nu
neutralino_1 and chargino_j -> W^- neutralino_1 -> l^- \nu neutralino_1. We
consider two classes of CP asymmetries. In the first class it must be possible
to distinguish between different leptonic chargino_j decay chains, whereas in
the second class this is not necessary. We consider also the 2-body decay
chargino_j -> W^- neutralino_1, and we assume that the momentum of the W boson
can be measured. Our framework is the minimal supersymmetric standard model
with complex parameters. The proposed CP asymmetries are non-vanishing due to
non-zero phases for the parameters \mu and/or A_b. We present numerical results
and estimate the observability of these CP asymmetries.Comment: 27 page
CP sensitive observables in chargino production with transverse beam polarization
We consider the process e^+e^-\to\ti\chi^+_i\ti\chi^-_j at a linear
collider with transverse beam polarization. We investigate the
influence of the CP phases on azimuthal asymmetries in
e^+e^-\to\ti\chi^+_i\ti\chi^-_j with subsequent two-body decays
\ti\chi^-_j\to \ti\nu_{\ell}\ell^- and \ti\chi^-_j\to W^-\ti\chi^0_1. We
show that triple product correlations involving the transverse beam
polarization vanish if at least one subsequent chargino decay is not observed.
We derive this result within the Minimal Supersymmetric Standard Model (MSSM)
with complex parameters, however, it holds also in the general MSSM with SUSY
flavour violation.Comment: 19 pages, 6 figure
Effect of boron doping on grain boundary cohesion in technically pure molybdenum investigated via meso-scale three-point-bending tests
Molybdenum has numerous advantageous functional and high-temperature properties. However, plastic deformation as well as structural applications are limited due to a propensity for brittle, intercrystalline failure, especially at low temperatures. It is well known that oxygen segregations have a detrimental effect, whereas it is assessed that carbon and/or boron have a beneficial effect on grain boundary cohesion. An advanced approach for the improvement of these interfaces is segregation engineering, e.g. the addition of cohesion enhancing elements segregating to the grain boundaries. To investigate early stages of crack formation, three-point bending tests on recrystallized commercially pure and boron micro-doped molybdenum were conducted between −28 \ub0C and room temperature. The tensile-loaded top surface of the specimens was examined post-mortem close to the final fracture area via scanning electron microscopy. The occurring separations of grains are investigated for distinct features and the chemical composition of the interface is complementary measured by atom probe tomography
Test of lepton flavour violation at LHC
We study lepton flavour violating decays of neutralinos and sleptons within
the Minimal Supersymmetric Standard Model, assuming two and three generation
mixings in the slepton sector. We take into account the most recent bounds on
flavour violating rare lepton decays. Taking the SPS1a' scenario as an example,
we show that some of the lepton flavour violating branching ratios of
neutralinos and sleptons can be sizable (~ 5-10%). We study the impact of the
lepton flavour violating neutralino and slepton decays on the di-lepton mass
distributions measured at LHC. We find that they can result in novel and
characteristic edge structures in the distributions. In particular, double-edge
structures can appear in the e tau and mu tau mass spectra if ~tau_1 is the
lightest slepton. The appearance of these remarkable structures provides a
powerful test of supersymmetric lepton flavour violation at LHC.Comment: 15 page
Effects of microstructure and crystallography on crack path and intrinsic resistance to shear-mode fatigue crack growth
The paper focuses on the effective resistance and the near-threshold growth mechanisms in theferritic-pearlitic and the pure pearlitic steel. The influence of microstructure on the shear-mode fatigue crackgrowth is divided here into two factors: the crystal lattice type and the presence of different phases.Experiments were done on ferritic-pearlitic steel and pearlitic steel using three different specimens, for whichthe effective mode II and mode III threshold values were measured and fracture surfaces were reconstructed inthree dimensions using stereophotogrammetry in scanning electron microscope. The ferritic-pearlitic andpearlitic steels showed a much different behaviour of modes II and III cracks than that of the ARMCO iron.Both the deflection angle and the mode II threshold were much higher and comparable to the austenitic steel.Mechanism of shear-mode crack behaviour in the ARMCO iron, titanium and nickel were described by themodel of emission of dislocations from the crack tip under a dominant mode II loading. In other testedmaterials the cracks propagated under a dominance of the local mode I. In the ferritic-pearlitic and pearliticsteels, the reason for such behaviour was the presence of the secondary-phase particles (cementite lamellas),unlike in the previously austenitic steel, where the fcc structure and the low stacking fault energy were the mainfactors. A criterion for mode I deflection from the mode II crack-tip loading, which uses values of the effectivemode I and mode II thresholds, was in agreement with fractographical observations
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