12,103 research outputs found
Right-handed charged currents in the era of the Large Hadron Collider
We discuss the phenomenology of right-handed charged currents in the
framework of the Standard Model Effective Field Theory, in which they arise due
to a single gauge-invariant dimension-six operator. We study the manifestations
of the nine complex couplings of the to right-handed quarks in collider
physics, flavor physics, and low-energy precision measurements. We first obtain
constraints on the couplings under the assumption that the right-handed
operator is the dominant correction to the Standard Model at observable
energies. We subsequently study the impact of degeneracies with other
Beyond-the-Standard-Model effective interactions and identify observables, both
at colliders and low-energy experiments, that would uniquely point to
right-handed charged currents.Comment: 50 pages plus appendices and reference
Image Ellipticity from Atmospheric Aberrations
We investigate the ellipticity of the point-spread function (PSF) produced by
imaging an unresolved source with a telescope, subject to the effects of
atmospheric turbulence. It is important to quantify these effects in order to
understand the errors in shape measurements of astronomical objects, such as
those used to study weak gravitational lensing of field galaxies. The PSF
modeling involves either a Fourier transform of the phase information in the
pupil plane or a ray-tracing approach, which has the advantage of requiring
fewer computations than the Fourier transform. Using a standard method,
involving the Gaussian weighted second moments of intensity, we then calculate
the ellipticity of the PSF patterns. We find significant ellipticity for the
instantaneous patterns (up to more than 10%). Longer exposures, which we
approximate by combining multiple (N) images from uncorrelated atmospheric
realizations, yield progressively lower ellipticity (as 1 / sqrt(N)). We also
verify that the measured ellipticity does not depend on the sampling interval
in the pupil plane using the Fourier method. However, we find that the results
using the ray-tracing technique do depend on the pupil sampling interval,
representing a gradual breakdown of the geometric approximation at high spatial
frequencies. Therefore, ray tracing is generally not an accurate method of
modeling PSF ellipticity induced by atmospheric turbulence unless some
additional procedure is implemented to correctly account for the effects of
high spatial frequency aberrations. The Fourier method, however, can be used
directly to accurately model PSF ellipticity, which can give insights into
errors in the statistics of field galaxy shapes used in studies of weak
gravitational lensing.Comment: 9 pages, 5 color figures (some reduced in size). Accepted for
publication in the Astrophysical Journa
Combining economic and social goals in the design of production systems by using ergonomics standards
In designing of production systems, economic and social goals can be combined, if ergonomics is integrated into the design process. More than 50 years of ergonomics research and practice have resulted in a large number of ergonomics standards for designing physical and organizational work environments. This paper gives an overview of the 174 international ISO and European CEN standards in this field, and discusses their applicability in design processes. The available standards include general recommendations for integrating ergonomics into the design process, as well as specific requirements for manual handling, mental load, task design, human-computer-interaction, noise, heat, body measurements, and other topics. The standards can be used in different phases of the design process: allocation of system functions between humans and machines, design of the work organization, work tasks and jobs, design of work environment, design of work equipment, hardware and software, and design of workspace and workstation. The paper is meant to inform engineers and managers involved in the design of production systems about the existence of a large number of ISO and CEN standards on ergonomics, which can be used to optimize human well-being and overall system performance.review;standard;standardization;ergonomics;CEN;ISO;human factors;production engineering;production planning
Modification of the simple mass balance equation for calculation of critical loads of acidity.
Over the last few years, the simple mass balance equation for the calculation of critical loads of acidity has been gradually modified as the underlying critical load concepts have developed and as problems with particular forms of the equation have been identified, through application in particular countries. The first major update of the equation took place following a workshop held in Vienna, Austria (Hojesky et al. 1993). The workshop was held to discuss problems which had been identified when the then current form of the equation was applied in countries with high rainfall. The problems had largely arisen because of simplifications and assumptions incorporated into the early formulation of the equation. The equation was reformulated to overcome the problems identified at the workshop. However, further problems were identified when the reformulated equation was applied in the UK in situations with a combination of high rainfall, large marine inputs and widespread occurrence of organic soils. A small workshop was, therefore held in Grange-over-Sands, UK in late 1993 to dicuss the problems and to further re-evaluate the equation. The problems had arisen in the UK because of simplifications and assumptions made in the formulation concerning, in particular, cation leaching and uptake. As a result, a more rigorous treatment of these variables was incorporated into the equation. The reformulation of the equation, as derived at the September 1993 workshop is described below
Co-creation in social media platforms: End-users as innovation partners: Online co-innovation within the open discovery space
Innovation is a way of meeting changing public needs by developing new and better solutions; it is also one of the most extensively discussed issues in the academic literature and field practice. Changing students’ behaviour, increasing knowledge development, increasing parents’ involvement and new teaching methods that overtake the existing methods creates a certain necessity to develop new knowledge media in collaboration with all educational stakeholders. Under increasing competition and market pressure the innovation process has been subject to important transformation during the last 30 years. Educational publishers changed from being traditionally a “closed’, internal process, based on internal organisational expertise and structures (R&D, New Product Department, New product Management etc.) the innovation process is increasingly becoming externally oriented. Chesbrough (2003) popularized the trend of externalizing the innovation process by engaging innovation partners in what he called the Open Innovation model. With the explosion of the social media and the subsequent public empowerment the innovation process is becoming a domain where the end-users and stakeholders are often directly involved (Prahalad and Ramaswamy, 2004); Crowdsourcing and innovation with the end-users and stakeholders is becoming the new innovation norm after closed- and open innovation. In this paper we identify this trend as Online Co-Innovation and explain its main merits in relation to the implementation of the Open Discovery Space project in the Netherlands
CP-violating axion interactions in effective field theory
Axions are introduced to explain the observed smallness of the
term of QCD. Standard Model extensions typically contain new sources of CP
violation, for instance to account for the baryon asymmetry of the universe. In
the presence of additional CP-violating sources a Peccei-Quinn mechanism does
not remove all CP violation, leading to CP-odd interactions among axions and
Standard Model fields. In this work, we use effective field theory to
parametrize generic sources of beyond-the-Standard-Model CP violation. We
systematically compute the resulting CP-odd couplings of axions to leptons and
hadrons by using chiral perturbation theory. We discuss in detail the
phenomenology of the CP-odd axion couplings and compare limits from axion
searches, such as fifth force and monopole-dipole searches and astrophysics, to
direct limits on the CP-violating operators from electric dipole moment
experiments. While limits from electric dipole moment searches are tight, the
proposed ARIADNE experiment can potentially improve the existing constraints in
a window of axion masses
The Astrophysical Multipurpose Software Environment
We present the open source Astrophysical Multi-purpose Software Environment
(AMUSE, www.amusecode.org), a component library for performing astrophysical
simulations involving different physical domains and scales. It couples
existing codes within a Python framework based on a communication layer using
MPI. The interfaces are standardized for each domain and their implementation
based on MPI guarantees that the whole framework is well-suited for distributed
computation. It includes facilities for unit handling and data storage.
Currently it includes codes for gravitational dynamics, stellar evolution,
hydrodynamics and radiative transfer. Within each domain the interfaces to the
codes are as similar as possible. We describe the design and implementation of
AMUSE, as well as the main components and community codes currently supported
and we discuss the code interactions facilitated by the framework.
Additionally, we demonstrate how AMUSE can be used to resolve complex
astrophysical problems by presenting example applications.Comment: 23 pages, 25 figures, accepted for A&
Relativistic Hartree approach with exact treatment of vacuum polarization for finite nuclei
We study the relativistic Hartree approach with the exact treatment of the
vacuum polarization in the Walecka sigma-omega model. The contribution from the
vacuum polarization of nucleon-antinucleon field to the source term of the
meson fields is evaluated by performing the energy integrals of the Dirac Green
function along the imaginary axis. With the present method of the vacuum
polarization in finite system, the total binding energies and charge radii of
16O and 40Ca can be reproduced. On the other hand, the level-splittings in the
single-particle level, in particular the spin-orbit splittings, are not
described nicely because the inclusion of vacuum effect provides a large
effective mass with small meson fields. We also show that the derivative
expansion of the effective action which has been used to calculate the vacuum
contribution for finite nuclei gives a fairly good approximation.Comment: 15 pages, 8 figure
A new limit on the Ultra-High-Energy Cosmic-Ray flux with the Westerbork Synthesis Radio Telescope
A particle cascade (shower) in a dielectric, for example as initiated by an
ultra-high energy cosmic ray, will have an excess of electrons which will emit
coherent \v{C}erenkov radiation, known as the Askaryan effect. In this work we
study the case in which such a particle shower occurs in a medium just below
its surface. We show, for the first time, that the radiation transmitted
through the surface is independent of the depth of the shower below the surface
when observed from far away, apart from trivial absorption effects. As a direct
application we use the recent results of the NuMoon project, where a limit on
the neutrino flux for energies above \,eV was set using the Westerbork
Synthesis Radio Telescope by measuring pulsed radio emission from the Moon, to
set a limit on the flux of ultra-high-energy cosmic rays.Comment: Accepted for publication in Phys. Rev.
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