50 research outputs found
Probing anomalous top quark interactions at the Fermilab Tevatron Collider
We study the effects of dimension-six operators contributing to the vertex in top quark pair production at the Tevatron collider. We derive both
the limits from Run 1 data and the potential bounds from future runs (Run 2 and
3). Although the current constraints are not very strong, the future runs are
quite effective in probing these operators. We investigate the possibility of
disentangling different operators with the invariant mass
distribution and the top quark polarization asymmetry. We also study the
effects of a different set of operators contributing to single top production
via the coupling. We derive the current and potential future bounds
on these anomalous operators and find that the upgraded Tevatron can improve
the existing constraints from for one of the operators.Comment: 20 pages, 2 figures, REVTEX, some clarifying remarks adde
R-parity violation and top quark polarization at the Fermilab Tevatron collider
The lepton or baryon number violating top quark interactions in the
supersymmetric standard model with R parity violation contribute to the process
d dbar to t tbar at the tree level via the t- or u-channel sfermion exchange.
Since these interactions are chiral, they induce polarization to the top quark
in the t tbar events at hadron colliders. We show in this article that the
polarization can be a useful observable for probing these interactions at the
upgraded Fermilab Tevatron collider, because the polarization is expected to be
very small in the standard model.Comment: 15 pages, 5 figure
The fully differential single-top-quark cross section in next-to-leading order QCD
We present a new next-to-leading order calculation for fully differential
single-top-quark final states. The calculation is performed using phase space
slicing and dipole subtraction methods. The results of the methods are found to
be in agreement. The dipole subtraction method calculation retains the full
spin dependence of the final state particles. We show a few numerical results
to illustrate the utility and consistency of the resulting computer
implementations.Comment: 37 pages, latex, 2 ps figure
Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign
Abstract: In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass ∼6.5 × 109 M ⊙. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87’s spectrum. We can exclude that the simultaneous γ-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the γ-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded
Direct Writing on Paper of Foldable Capacitive Touch Pads with Silver Nanowire Inks
Paper-based capacitive touch pads
can be fabricated utilizing high-concentration silver nanowire inks
needle-printed directly onto paper substrates through a 2D programmable
platform. Post deposition, silver nanowire tracks can be photonically
sintered using a camera flash to reduce sheet resistance similar to
thermal sintering approaches. Touch pad sensors on a variety of paper
substrates can be achieved with optimized silver nanowire tracks.
Rolling and folding trials, which yielded only modest changes in capacitance
and no loss of function, coupled with touch pad functionality on curved
surfaces, suggest sufficient flexibility and durability for paper
substrate touch pads to be used in diverse applications. A simplified
model to predict touch pad capacitance variation ranges with differing
touch conditions was developed, with good agreement against experimental
results. Such paper-based touch pads have the advantage of simple
structure, easy fabrication, and fast sintering, which holds promise
for numerous commercial applications including low-cost portable devices
where ultrathin and lightweight features, coupled with reliable bending
stability are desirable
Determination of Pharmaceutical Residues in Fish Bile by Solid-Phase Microextraction Couple with Liquid Chromatography-Tandem Mass Spectrometry (LC/MS/MS)
The present study investigates possible uptake and bioconcentration
of different classes of pharmaceuticals residues (organic contaminants)
in fish bile using a simplified analytical methodology based on solid
phase microextration (SPME). The use of solid phase microextraction
(SPME), as a simple analytical tool, to screen for target pharmaceuticals
in fish bile samples was validated in rainbow trout (<i>Oncorhynchus
mykiss</i>) following short-term laboratory exposures to carbamazepine
and fluoxetine. While fish bioconcentrated both fluoxetine and carbamazepine
from exposure water, fluoxetine accumulated to a greater degree in
bile than carbamazepine. Good agreement was obtained for both analytes
in bile samples between SPME and traditional liquid (solvent) extraction
approaches (R<sup>2</sup> > 0.99). The field application of SPME
sampling
was further demonstrated in fathead minnow (<i>Pimephales promelas</i>), a small-bodied fish caged upstream and downstream of a local wastewater
treatment plant where fluoxetine, atorvastatin, and sertraline were
detected in fish bile at the downstream location. SPME is a promising
analytical tool for investigating the bioconcentration of trace contaminants
in fish bile, facilitating detection of trace environmental contaminants
otherwise undetectable due to low concentrations in the environment
and biological tissues as well as the complexity of the sample matrices