2,588 research outputs found
Magnetic Moments of Baryons with a Heavy Quark
We compute magnetic moments of baryons with a heavy quark in the bound state
approach for heavy baryons. In this approach the heavy baryon is considered as
a heavy meson bound to a light baryon. The latter is represented as a soliton
excitation of light meson fields. We obtain the magnetic moments by sandwiching
pertinent components of the electromagnetic current operator between the bound
state wave--functions. We extract this current operator from the coupling to
the photon field after extending the action to be gauge invariant.Comment: Talk presented by HW at MRST'03 (Joe-Fest), Syracuse, NY, May 2003,
12 pages, uses AIP style files. Ref. adde
Autoplot: A browser for scientific data on the web
Autoplot is software developed for the Virtual Observatories in Heliophysics
to provide intelligent and automated plotting capabilities for many typical
data products that are stored in a variety of file formats or databases.
Autoplot has proven to be a flexible tool for exploring, accessing, and viewing
data resources as typically found on the web, usually in the form of a
directory containing data files with multiple parameters contained in each
file. Data from a data source is abstracted into a common internal data model
called QDataSet. Autoplot is built from individually useful components, and can
be extended and reused to create specialized data handling and analysis
applications and is being used in a variety of science visualization and
analysis applications. Although originally developed for viewing
heliophysics-related time series and spectrograms, its flexible and generic
data representation model makes it potentially useful for the Earth sciences.Comment: 16 page
Near-BPS Skyrmions: Non-shell configurations and Coulomb effects
The relatively small binding energy in nuclei suggests that they may be well
represented by near-BPS Skyrmions since their mass is roughly proportional to
the baryon number For that purpose, we propose a generalization of the
Skyrme model with terms up to order six in derivatives of the pion fields and
treat the nonlinear and Skyrme terms as small perturbations. For our
special choice of mass term (or potential) , we obtain well-behaved
analytical BPS-type solutions with non-shell configurations for the baryon
density, as opposed to the more complex shell-like configurations found in most
extensions of the Skyrme model . Along with static and (iso)rotational
energies, we add to the mass of the nuclei the often neglected Coulomb energy
and isospin breaking term. Fitting the four model parameters, we find a
remarkable agreement for the binding energy per nucleon with respect to
experimental data. These results support the idea that nuclei could be near-BPS
Skyrmions.Comment: Correction of minors errors, references adde
Chiral Quark Model
In this talk I review studies of hadron properties in bosonized chiral quark
models for the quark flavor dynamics. Mesons are constructed from
Bethe--Salpeter equations and baryons emerge as chiral solitons. Such models
require regularization and I show that the two--fold Pauli--Villars
regularization scheme not only fully regularizes the effective action but also
leads the scaling laws for structure functions. For the nucleon structure
functions the present approach serves to determine the regularization
prescription for structure functions whose leading moments are not given by
matrix elements of local operators. Some numerical results are presented for
the spin structure functions.Comment: Talk presented at the workshop QCD 2002, IIT Kanpur, Nov. 2002, 10
pages, proceedings style files include
A new BIST scheme for low-power and high-resolution DAC testing
A BIST scheme for testing on chip DAC is presented in this paper. We discuss the generation of on chip testing stimuli and the measurement of digital signals with a narrow-band digital filter. We validate the scheme with software simulation and point out the possibility of ADC BIST with verified DACicus-journals
Visual exploration and retrieval of XML document collections with the generic system X2
This article reports on the XML retrieval system X2 which has been developed at the University of Munich over the last five years. In a typical session with X2, the user
first browses a structural summary of the XML database in order to select interesting elements and keywords occurring in documents. Using this intermediate result, queries combining structure and textual references are composed semiautomatically.
After query evaluation, the full set of answers is presented in a visual and structured way. X2 largely exploits the structure found in documents, queries and answers to enable new interactive visualization and exploration techniques that support mixed IR and database-oriented querying, thus bridging the gap between these three views on the data to be retrieved. Another salient characteristic of X2 which distinguishes it from other visual query systems for XML is that it supports various degrees of detailedness in the presentation of answers, as well as techniques for dynamically reordering and grouping retrieved elements once the complete answer set has been computed
Instability of the hedgehog shape for the octet baryon in the chiral quark soliton model
In this paper the stability of the hedgehog shape of the chiral soliton is
studied for the octet baryon with the SU(3) chiral quark soliton model. The
strangeness degrees of freedom are treated by a simplified bound-state
approach, which omits the locality of the kaon wave function. The mean field
approximation for the flavor rotation is applied to the model. The classical
soliton changes shape according to the strangeness. The baryon appears as a
rotational band of the combined system of the deformed soliton and the kaon.Comment: 24 pages, LaTeX, 8 eps file
Interpretation of F106B and CV580 in-flight lightning data and form factor determination
Two topics of in-flight aircraft/lightning interaction are addressed. The first is the analysis of measured data from the NASA F106B Thunderstorm Research Aircraft and the CV580 research program run by the FAA and Wright-Patterson Air Force Base. The CV580 data was investigated in a mostly qualitative sense, while the F106B data was subjected to both statistical and quantitative analysis using linear triggered lightning finite difference models. The second main topic is the analysis of field mill data and the calibration of the field mill systems. The calibration of the F106B field mill system was investigated using an improved finite difference model of the aircraft having a spatial resolution of one-quarter meter. The calibration was applied to measured field mill data acquired during the 1985 thunderstorm season. The experimental determination of form factors useful for field mill calibration was also investigated both experimentally and analytically. The experimental effort involved the use of conducting scale models and an electrolytic tank. An analytic technique was developed to aid in the understanding of the experimental results
Observations of meteoric material and implications for aerosol nucleation in the winter Arctic lower stratosphere derived from in situ particle measurements
Number concentrations of total and non-volatile aerosol particles with size diameters >0.01 μm as well as particle size distributions (0.4–23 μm diameter) were measured in situ in the Arctic lower stratosphere (10–20.5 km altitude). The measurements were obtained during the campaigns European Polar Stratospheric Cloud and Lee Wave Experiment (EUPLEX) and Envisat-Arctic-Validation (EAV). The campaigns were based in Kiruna, Sweden, and took place from January to March 2003. Measurements were conducted onboard the Russian high-altitude research aircraft Geophysica using the low-pressure Condensation Nucleus Counter COPAS (COndensation PArticle Counter System) and a modified FSSP 300 (Forward Scattering Spectrometer Probe). Around 18–20 km altitude typical total particle number concentrations nt range at 10–20 cm−3 (ambient conditions). Correlations with the trace gases nitrous oxide (N2O) and trichlorofluoromethane (CFC-11) are discussed. Inside the polar vortex the total number of particles >0.01 μm increases with potential temperature while N2O is decreasing which indicates a source of particles in the above polar stratosphere or mesosphere. A separate channel of the COPAS instrument measures the fraction of aerosol particles non-volatile at 250°C. Inside the polar vortex a much higher fraction of particles contained non-volatile residues than outside the vortex (~67% inside vortex, ~24% outside vortex). This is most likely due to a strongly increased fraction of meteoric material in the particles which is transported downward from the mesosphere inside the polar vortex. The high fraction of non-volatile residual particles gives therefore experimental evidence for downward transport of mesospheric air inside the polar vortex. It is also shown that the fraction of non-volatile residual particles serves directly as a suitable experimental vortex tracer. Nanometer-sized meteoric smoke particles may also serve as nuclei for the condensation of gaseous sulfuric acid and water in the polar vortex and these additional particles may be responsible for the increase in the observed particle concentration at low N2O. The number concentrations of particles >0.4 μm measured with the FSSP decrease markedly inside the polar vortex with increasing potential temperature, also a consequence of subsidence of air from higher altitudes inside the vortex. Another focus of the analysis was put on the particle measurements in the lowermost stratosphere. For the total particle density relatively high number concentrations of several hundred particles per cm3 at altitudes below ~14 km were observed in several flights. To investigate the origin of these high number concentrations we conducted air mass trajectory calculations and compared the particle measurements with other trace gas observations. The high number concentrations of total particles in the lowermost stratosphere are probably caused by transport of originally tropospheric air from lower latitudes and are potentially influenced by recent particle nucleation
CP-violating asymmetry in in the Skyrme model
We study the CP-violating asymmetry in nonleptonic decay .
By employing the Skyrme model to calculate this decay amplitude contributed by
the gluonic diploe operator, we find a possible large CP-violating asymmetry
could be expected, which is consistent with the previous study.Comment: LaTeX file, To appear in J Phys G: Nucl Phys and Part Phy
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