1,747 research outputs found
Hadronic production of bottom-squark pairs with electroweak contributions
We present the complete computation of the tree-level and the next-to-leading
order electroweak contributions to bottom-squark pair production at the LHC.
The computation is performed within the minimal supersymmetric extension of the
Standard Model. We discuss the numerical impact of these contributions in
several supersymmetric scenarios.Comment: 33 pages, v2: preprint numbers correcte
Rapid Tooling Method for Soft Customized Removable Oral Appliances
Traditionally oral appliances i.e. removable orthodontic appliances, bite splints and snoring / sleep apnea appliances are made with alginate impressions and wax registrations. Our aim was to describe the process of manufacturing customized oral appliances with a new technique i.e. rapid tooling method. The appliance should ideally be custom made to match the teeth. An orthodontic patient, scheduled for conventional orthodontic treatment, served as a study subject. After a precise clinical and radiographic examination, the approach was to digitize the patient’s dental arches and then to correct them virtually by computer. Additive manufacturing was then used to fabricate a mould for a soft customized appliance. The mould was manufactured using stereolithography from Somos ProtoGen O-XT 18420 material. Casting material for the mould to obtain the final appliance was silicone. As a result we managed to create a customized soft orthodontic appliance. Also, the accuracy of the method was found to be adequate. Two versions of the described device were manufactured: one with small and one with moderate orthodontic force. The study person also gave information on the subjective patient adaptation aspects of the oral appliance
Next-to-leading order QCD predictions for production at LHC
We calculate the complete next-to-leading order (NLO) QCD corrections to the
production in association with a jet at the LHC. We study the impacts
of the NLO QCD radiative corrections to the integrated and differential cross
sections and the dependence of the cross section on the
factorization/renormalization scale. We present the transverse momentum
distributions of the final -, Higgs-boson and leading-jet. We find that
the NLO QCD corrections significantly modify the physical observables, and
obviously reduce the scale uncertainty of the LO cross section. The QCD
K-factors can be 1.183 and 1.180 at the and
LHC respectively, when we adopt the inclusive event selection scheme with
, and . Furthermore, we make the comparison between the two scale
choices, and , and find the scale choice seems to be more
appropriate than the fixed scale .Comment: 18 pages, 7 figure
Electrically controlled long-distance spin transport through an antiferromagnetic insulator
Spintronics uses spins, the intrinsic angular momentum of electrons, as an
alternative for the electron charge. Its long-term goal is in the development
of beyond-Moore low dissipation technology devices. Recent progress
demonstrated the long-distance transport of spin signals across ferromagnetic
insulators. Antiferromagnetically ordered materials are however the most common
class of magnetic materials with several crucial advantages over ferromagnetic
systems. In contrast to the latter, antiferromagnets exhibit no net magnetic
moment, which renders them stable and impervious to external fields. In
addition, they can be operated at THz frequencies. While fundamentally their
properties bode well for spin transport, previous indirect observations
indicate that spin transmission through antiferromagnets is limited to short
distances of a few nanometers. Here we demonstrate the long-distance, over tens
of micrometers, propagation of spin currents through hematite (\alpha-Fe2O3),
the most common antiferromagnetic iron oxide, exploiting the spin Hall effect
for spin injection. We control the spin current flow by the interfacial
spin-bias and by tuning the antiferromagnetic resonance frequency with an
external magnetic field. This simple antiferromagnetic insulator is shown to
convey spin information parallel to the compensated moment (N\'eel order) over
distances exceeding tens of micrometers. This newly-discovered mechanism
transports spin as efficiently as the net magnetic moments in the best-suited
complex ferromagnets. Our results pave the way to ultra-fast, low-power
antiferromagnet-insulator-based spin-logic devices that operate at room
temperature and in the absence of magnetic fields
Inadequacy of zero-width approximation for a light Higgs boson signal
In the Higgs search at the LHC, a light Higgs boson (115 GeV <~ M_H <~ 130
GeV) is not excluded by experimental data. In this mass range, the width of the
Standard Model Higgs boson is more than four orders of magnitude smaller than
its mass. The zero-width approximation is hence expected to be an excellent
approximation. We show that this is not always the case. The inclusion of
off-shell contributions is essential to obtain an accurate Higgs signal
normalisation at the 1% precision level. For gg (-> H) -> VV, V= W,Z, O(10%)
corrections occur due to an enhanced Higgs signal in the region M_VV > 2 M_V,
where also sizable Higgs-continuum interference occurs. We discuss how
experimental selection cuts can be used to exclude this region in search
channels where the Higgs invariant mass cannot be reconstructed. We note that
the H -> VV decay modes in weak boson fusion are similarly affected.Comment: 26 pages, 18 figures, 6 tables; added references, expanded
introduction, version to appear in JHE
Electroweak corrections to W-boson pair production at the LHC
Vector-boson pair production ranks among the most important Standard-Model
benchmark processes at the LHC, not only in view of on-going Higgs analyses.
These processes may also help to gain a deeper understanding of the electroweak
interaction in general, and to test the validity of the Standard Model at
highest energies. In this work, the first calculation of the full one-loop
electroweak corrections to on-shell W-boson pair production at hadron colliders
is presented. We discuss the impact of the corrections on the total cross
section as well as on relevant differential distributions. We observe that
corrections due to photon-induced channels can be amazingly large at energies
accessible at the LHC, while radiation of additional massive vector bosons does
not influence the results significantly.Comment: 29 pages, 15 figures, 4 tables; some references and comments on
\gamma\gamma -> WW added; matches version published in JHE
NLO QCD bottom corrections to Higgs boson production in the MSSM
We present a calculation of the two-loop bottom-sbottom-gluino contributions
to Higgs boson production via gluon fusion in the MSSM. The calculation is
based on an asymptotic expansion in the masses of the supersymmetric particles,
which are assumed to be much heavier than the bottom quark and the Higgs
bosons. We obtain explicit analytic results that allow for a straightforward
identification of the dominant contributions in the NLO bottom corrections. We
emphasize the interplay between the calculations of the masses and the
production cross sections of the Higgs bosons, discussing sensible choices of
renormalization scheme for the parameters in the bottom/sbottom sector.Comment: 25 pages, 4 figures. v2: references and two figures added, version
published in JHE
Automation of one-loop QCD corrections
We present the complete automation of the computation of one-loop QCD
corrections, including UV renormalization, to an arbitrary scattering process
in the Standard Model. This is achieved by embedding the OPP integrand
reduction technique, as implemented in CutTools, into the MadGraph framework.
By interfacing the tool so constructed, which we dub MadLoop, with MadFKS, the
fully automatic computation of any infrared-safe observable at the
next-to-leading order in QCD is attained. We demonstrate the flexibility and
the reach of our method by calculating the production rates for a variety of
processes at the 7 TeV LHC.Comment: 64 pages, 12 figures. Corrected the value of m_Z in table 1. In table
2, corrected the values of cross sections in a.4 and a.5 (previously computed
with mu=mtop/2 rather than mu=mtop/4). In table 2, corrected the values of
NLO cross sections in b.3, b.6, c.3, and e.7 (the symmetry factor for a few
virtual channels was incorrect). In sect. A.4.3, the labeling of the
four-momenta was incorrec
The Passive Yet Successful Way of Planktonic Life: Genomic and Experimental Analysis of the Ecology of a Free-Living Polynucleobacter Population
Background: The bacterial taxon Polynucleobacter necessarius subspecies asymbioticus represents a group of planktonic freshwater bacteria with cosmopolitan and ubiquitous distribution in standing freshwater habitats. These bacteria comprise,1 % to 70 % (on average about 20%) of total bacterioplankton cells in various freshwater habitats. The ubiquity of this taxon was recently explained by intra-taxon ecological diversification, i.e. specialization of lineages to specific environmental conditions; however, details on specific adaptations are not known. Here we investigated by means of genomic and experimental analyses the ecological adaptation of a persistent population dwelling in a small acidic pond. Findings: The investigated population (F10 lineage) contributed on average 11 % to total bacterioplankton in the pond during the vegetation periods (ice-free period, usually May to November). Only a low degree of genetic diversification of the population could be revealed. These bacteria are characterized by a small genome size (2.1 Mb), a relatively small number of genes involved in transduction of environmental signals, and the lack of motility and quorum sensing. Experiments indicated that these bacteria live as chemoorganotrophs by mainly utilizing low-molecular-weight substrates derived from photooxidation of humic substances. Conclusions: Evolutionary genome streamlining resulted in a highly passive lifestyle so far only known among free-living bacteria from pelagic marine taxa dwelling in environmentally stable nutrient-poor off-shore systems. Surprisingly, such a lifestyle is also successful in a highly dynamic and nutrient-richer environment such as the water column of the investigate
Higgs Boson Masses in the Complex NMSSM at One-Loop Level
The Next-to-Minimal Supersymmetric Extension of the Standard Model (NMSSM)
with a Higgs sector containing five neutral and two charged Higgs bosons allows
for a rich phenomenology. In addition, the plethora of parameters provides many
sources of CP violation. In contrast to the Minimal Supersymmetric Extension,
CP violation in the Higgs sector is already possible at tree-level. For a
reliable understanding and interpretation of the experimental results of the
Higgs boson search, and for a proper distinction of Higgs sectors provided by
the Standard Model or possible extensions, the Higgs boson masses have to be
known as precisely as possible including higher-order corrections. In this
paper we calculate the one-loop corrections to the neutral Higgs boson masses
in the complex NMSSM in a Feynman diagrammatic approach adopting a mixed
renormalization scheme based on on-shell and conditions. We study
various scenarios where we allow for tree-level CP-violating phases in the
Higgs sector and where we also study radiatively induced CP violation due to a
non-vanishing phase of the trilinear coupling in the stop sector. The
effects on the Higgs boson phenomenology are found to be significant. We
furthermore estimate the theoretical error due to unknown higher-order
corrections by both varying the renormalization scheme of the top and bottom
quark masses and by adopting different renormalization scales. The residual
theoretical error can be estimated to about 10%
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