4,354 research outputs found
b anti-b Higgs production at the LHC: Yukawa corrections and the leading Landau singularity
At tree-level Higgs production in association with a b-quark pair proceeds
through the small Yukawa bottom coupling in the Standard Model. Even in the
limit where this coupling vanishes, electroweak one-loop effects, through the
top-Higgs Yukawa coupling in particular, can still trigger this reaction. This
contribution is small for Higgs masses around 120GeV but it quickly picks up
for higher Higgs masses especially because the one-loop amplitude develops a
leading Landau singularity and new thresholds open up. These effects can be
viewed as the production of a pair of top quarks which rescatter to give rise
to Higgs production through WW fusion. We study the leading Landau singularity
in detail. Since this singularity is not integrable when the one-loop amplitude
is squared, we regulate the cross section by taking into account the width of
the internal top and W particles. This requires that we extend the usual box
one-loop function to the case of imaginary masses. We show how this can be
implemented analytically in our case. We study in some detail the cross section
at the LHC as a function of the Higgs mass and show how some distributions can
be drastically affected compared to the tree-level result.Comment: 48 pages, 20 figures. Phys.Rev.D accepted version. Conclusions
unchanged, minor changes and references adde
Optical properties of a light-emitting polymer directly patterned by soft lithography
Copyright © 2002 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Applied Physics Letters 81 (2002) and may be found at http://link.aip.org/link/?APPLAB/81/1955/1We present the optical properties of a directly patterned light-emitting polymer. The patterned poly(2-methoxy-5-(3',7'-dimethyloctyloxy)-paraphenylenevinylene film is fabricated using hot embossing lithography. The effect of the embossed microstructure on the light emitted from the polymer is examined by measuring the angle-dependent photoluminescence and its photonic band structure. The imposed grating modifies the emitted light by Bragg scattering into free space light that would otherwise be trapped as waveguide modes. This simple patterning technique may find application in improving the performance of light-emitting polymer devices
Family Quality of Life Following Early Identification of Deafness
This is the published version, also available here: http://dx.doi.org/10.1044/0161-1461(2009/07-0093).Purpose: Family members’ perceptions of their
quality of life were examined following early identification of
deafness in children.
Method: A questionnaire was used to solicit ratings of satisfaction
from the family members of 207 children who were deaf and
younger than 6 years of age.
Results: Results indicated that families were generally satisfied
with the areas of family life surveyed. Descriptive analysis
suggested lower satisfaction ratings in the area of emotional wellbeing.
Families also reported that their child’s deafness had the
largest impact on their emotional well-being. Family members of
children using oral communication with a cochlear implant
reported higher satisfaction with their child’s speech production
and perception outcomes than family members of children using
hearing aids alone.
Implications: We recommend that service providers and early
hearing detection and intervention program coordinators consider
additional supports for family well-being following the early
identification of deafness in children
Phase diagrams of correlated electrons: systematic corrections to the mean field theory
Perturbative corrections to the mean field theory for particle-hole
instabilities of interacting electron systems are computed within a scheme
which is equivalent to the recently developed variational approach to the
Kohn-Luttinger superconductivity. This enables an unbiased comparison of
particle-particle and particle-hole instabilities within the same approximation
scheme. A spin-rotation invariant formulation for the particle-hole
instabilities in the triplet channel is developed. The method is applied to the
phase diagram of the t-t' Hubbard model on the square lattice. At the Van Hove
density, antiferromagnetic and d-wave Pomeranchuk phases are found to be stable
close to half filling. However, the latter phase is confined to an extremely
narrow interval of densities and away from the singular filling, d-wave
superconducting instability dominates
SLIP4EX- a program for routine slope stability analysis to include the effects of vegetation, reinforcement and hydrological changes
SLIP4EX is a straightforward computer program developed in connection with the EU funded ECOSLOPES project for routine stability analysis and the assessment of the contribution of vegetation to slope stability. The slope section is drawn up and dimensions and parameters are fed in to the Microsoft Excel based program for stability calculations and comparisons of Factors of Safety using different methods of analysis (Bishop, Janbu, Fellenius, Simple, Greenwood). The background and assumptions involved in the derivation of each of the methods is briefly described. The simplicity of the program enables the user to understand the nature of the analysis, explore the parameter assumptions made and compare the different methods of analysis. Soil reinforcement by geosynthetic layers or anchors, and vegetation effects of enhanced cohesion, changed water pressures, mass of vegetation, wind forces and root reinforcement forces are readily included in the analysis. The program is freely available on request from the author
Direct calculation of the hard-sphere crystal/melt interfacial free energy
We present a direct calculation by molecular-dynamics computer simulation of
the crystal/melt interfacial free energy, , for a system of hard
spheres of diameter . The calculation is performed by thermodynamic
integration along a reversible path defined by cleaving, using specially
constructed movable hard-sphere walls, separate bulk crystal and fluid systems,
which are then merged to form an interface. We find the interfacial free energy
to be slightly anisotropic with = 0.62, 0.64 and
0.58 for the (100), (110) and (111) fcc crystal/fluid
interfaces, respectively. These values are consistent with earlier density
functional calculations and recent experiments measuring the crystal nucleation
rates from colloidal fluids of polystyrene spheres that have been interpreted
[Marr and Gast, Langmuir {\bf 10}, 1348 (1994)] to give an estimate of
for the hard-sphere system of , slightly lower
than the directly determined value reported here.Comment: 4 pages, 4 figures, submitted to Physical Review Letter
Inconsistency of the MLE for the joint distribution of interval censored survival times and continuous marks
This paper considers the nonparametric maximum likelihood estimator (MLE) for
the joint distribution function of an interval censored survival time and a
continuous mark variable. We provide a new explicit formula for the MLE in this
problem. We use this formula and the mark specific cumulative hazard function
of Huang and Louis (1998) to obtain the almost sure limit of the MLE. This
result leads to necessary and sufficient conditions for consistency of the MLE
which imply that the MLE is inconsistent in general. We show that the
inconsistency can be repaired by discretizing the marks. Our theoretical
results are supported by simulations.Comment: 27 pages, 4 figure
Gauge-invariant magnetic perturbations in perfect-fluid cosmologies
We develop further our extension of the Ellis-Bruni covariant and
gauge-invariant formalism to the general relativistic treatment of density
perturbations in the presence of cosmological magnetic fields. We present
detailed analysis of the kinematical and dynamical behaviour of perturbed
magnetized FRW cosmologies containing fluid with non-zero pressure. We study
the magnetohydrodynamical effects on the growth of density irregularities
during the radiation era. Solutions are found for the evolution of density
inhomogeneities on small and large scales in the presence of pressure, and some
new physical effects are identified.Comment: Revised version (some minor changes - few equations added). 26 pages.
No figures. To appear in Classical and Quantum Gravit
The national telephone plan - numbering [1959]
This article was originally published in the Telecommunication Journal of Australia Volume 12 No 1, 1959. It describes one of the basic elements in the design of the system for the long-term development of the Australian telephone service the national numbering plan
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