7,086 research outputs found
Search Strategies for Non-Standard Higgs Bosons at Future e^+e^- Colliders
Already in the simplest two-Higgs-doublet model with CP violation in the
Higgs sector, the mixing matrix for the neutral Higgs bosons can
substantially modify their couplings, thereby endangering the ``classical''
Higgs search strategies. However, there are sum rules relating Yukawa and
Higgs-Z couplings which ensure that the ZZ, b\anti b and t\anti t couplings
of a given neutral 2HDM Higgs boson cannot all be simultaneously suppressed.
This result implies that any single Higgs boson will be detectable at an e^+e^-
collider if the Z+Higgs, b\anti b+Higgs {\it and} t\anti t+Higgs production
channels are all kinematically accessible {\it and} if the integrated
luminosity is sufficient. We explore, as a function of Higgs mass, the
luminosity required to guarantee Higgs boson detection, and find that for
moderate values the needed luminosity is unlikely to be available
for all possible mixing scenarios. The additional difficulties for the case
when the two-doublet Higgs sector is extended by adding one more singlet are
summarized. Implications of the sum rules for Higgs discovery at the Tevatron
and LHC are briefly discussed.Comment: 16 pages, 4 postscript figures, references added in replacemen
Preventing Incomplete/Hidden Requirements: Reflections on Survey Data from Austria and Brazil
Many software projects fail due to problems in requirements engineering (RE).
The goal of this paper is analyzing a specific and relevant RE problem in
detail: incomplete/hidden requirements. We replicated a global family of RE
surveys with representatives of software organizations in Austria and Brazil.
We used the data to (a) characterize the criticality of the selected RE
problem, and to (b) analyze the reported main causes and mitigation actions.
Based on the analysis, we discuss how to prevent the problem. The survey
includes 14 different organizations in Austria and 74 in Brazil, including
small, medium and large sized companies, conducting both, plan-driven and agile
development processes. Respondents from both countries cited the
incomplete/hidden requirements problem as one of the most critical RE problems.
We identified and graphically represented the main causes and documented
solution options to address these causes. Further, we compiled a list of
reported mitigation actions. From a practical point of view, this paper
provides further insights into common causes of incomplete/hidden requirements
and on how to prevent this problem.Comment: in Proceedings of the Software Quality Days, 201
CBRN Threats and the Economic Analysis of Terrorism
The aim of this paper is to investigate the economic aspects of CBRN threats. For this purpose, the extent to which this topic is reflected in freely-accessible academic literature and the costs associated with such threats will be assessed. Furthermore, it is to be determined which industries have a particular interest in security against such CBRN threats.
Two-color QCD with staggered fermions at finite temperature under the influence of a magnetic field
In this paper we investigate the influence of a constant external magnetic
field on the finite-temperature phase structure and the chiral properties of a
simplified lattice model for QCD. We assume an SU(2) gauge symmetry and employ
dynamical staggered fermions of identical mass without rooting, corresponding
to Nf=4 flavors of identical electric charge. For fixed mass (given in lattice
units) the critical temperature is seen to rise with the magnetic field
strength. For three fixed beta-values, selected such that we stay (i) within
the chirally broken phase, (ii) within the transition region or (iii) within
the chirally restored phase, we study the approach to the chiral limit for
various values of the magnetic field. Within the chirally broken (confinement)
phase the chiral condensate is found to increase monotonically with a growing
magnetic field strength. In the chiral limit the increase starts linear in
agreement with a chiral model studied by Shushpanov and Smilga. Within the
chirally restored (deconfinement) phase the chiral condensate tends to zero in
the chiral limit, irrespective of the strength of the magnetic field.Comment: 15 pages, 12 figures; version accepted by Physical Review
A novel vacuum ultra violet lamp for metastable rare gas experiments
We report on a new design of a vacuum ultra violet (VUV) lamp for direct
optical excitation of high laying atomic states e.g. for excitation of
metastable rare gas atoms. The lamp can be directly mounted to ultra high
vacuum vessels (p <= 10^(-10) mbar). It is driven by a 2.45 GHz microwave
source. For optimum operation it requires powers of approximately 20 W. The VUV
light is transmitted through a magnesium fluoride window, which is known to
have a decreasing transmittance for VUV photons with time. In our special
setup, after a run-time of the VUV lamp of 550 h the detected signal
continuously decreased to 25 % of its initial value. This corresponds to a
lifetime increase of two orders of magnitude compared to previous setups or
commercial lamps
The W_L W_L scattering at the LHC: improving the selection criteria
We present a systematic study of the different mechanisms leading to WW pair
production at the LHC, both in the same-sign and opposite-sign channels, and we
emphasize that the former offers much better potential for investigating
non-resonant W_L W_L scattering. We propose a new kinematic variable to isolate
the W_L W_L scattering component in same-sign WW production at the LHC.
Focusing on purely leptonic W decay channels, we show that it considerably
improves the LHC capabilities to shed light on the electroweak symmetry
breaking mechanism after collecting 100 fb^{-1} of data at sqrt{s} = 14 TeV.
The new variable is less effective in the opposite-sign WW channel due to
different background composition.Comment: 25 pages, 32 figure
Elucidating structure-function relationships from molecule-to-cell-to-tissue: from research modalities to clinical realities
The National Academy of Engineering selected âImagingâ as one of the greatest engineering achievements of the 20th century (Greatest Engineering Achievements of the 20th Century. 2009 (cited 2008, November 10); available from: http://www.greatachievements.org/). The combination of different imaging modalities and technologies for mapping bimolecular and/or biological processes within single cells or even whole organs has extraordinary potential for revolutionizing the diagnosis and treatment of pathophysiological disorders, and thus for mitigating the significant social and economic costs associated with the clinical management of disease. Such integrated imaging approaches will eventually lead to individualized programs for disease prevention through advanced diagnosis, risk stratification and targeted cell therapies resulting in more successful and efficient health care. The goal of this article is to provide readers with a current update of selected of state-of-the-art imaging modalities which would likely to lead to improved clinical outcomes if employed in an integrated approach, including use of ultramicrosensors to detect reactive oxygen/nitrogen species in a single cell, use of electron tomography to visualize and characterize cellular organization in three dimensions (3D), and molecular imaging strategies to assess naturally occurring and therapeutic peripheral and myocardial angiogenesis using targeted radiolabeled tracers
A novel vacuum ultra violet lamp for metastable rare gas experiments
We report on a new design of a vacuum ultra violet (VUV) lamp for direct
optical excitation of high laying atomic states e.g. for excitation of
metastable rare gas atoms. The lamp can be directly mounted to ultra high
vacuum vessels (p <= 10^(-10) mbar). It is driven by a 2.45 GHz microwave
source. For optimum operation it requires powers of approximately 20 W. The VUV
light is transmitted through a magnesium fluoride window, which is known to
have a decreasing transmittance for VUV photons with time. In our special
setup, after a run-time of the VUV lamp of 550 h the detected signal
continuously decreased to 25 % of its initial value. This corresponds to a
lifetime increase of two orders of magnitude compared to previous setups or
commercial lamps
New proton polarized structure functions in charged current processes at HERA
Estimates for longitudinal spin asymmetries which single out new polarized
nucleon structure functions in deeply inelastic charged current interactions at
HERA energies are given, exploiting their interpretation in terms of polarized
quark distributions. These asymmetries turn out to be large and allow a
measurement of the new polarized structure functions and ,
which would add valuable tests and information on the spin content of quarks
inside a polarized proton. We also show that single spin asymmetries in neutral
current interactions are very small.Comment: LaTeX, 8 pages, 6 figure
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