314 research outputs found
Large-N_c operator analysis of 2-body meson-baryon counterterms in the chiral Lagrangian
The chiral SU(3) Lagrangian with the baryon octet and decuplet fields is
considered. The Q^2 counterterms involving the decuplet fields are constructed.
We derive the correlation of the chiral parameters implied by the 1/N_c
expansion at leading order in QCD.Comment: 20 pages, 3 figure
Strangeness in the baryon ground states
We compute the strangeness content of the baryon octet and decuplet states
based on an analysis of recent lattice simulations of the BMW, PACS, LHPC and
HSC groups for the pion-mass dependence of the baryon masses. Our results rely
on the relativistic chiral Lagrangian and large- sum rule estimates of the
counter terms relevant for the baryon masses at NLO. A partial summation is
implied by the use of physical baryon and meson masses in the one-loop
contributions to the baryon self energies. A simultaneous description of the
lattice results of the BMW, LHPC, PACS and HSC groups is achieved. From a
global fit we determine the axial coupling constants and in agreement with their values extracted from semi-leptonic
decays of the baryons. Moreover, various flavor symmetric limits of baron octet
and decuplet masses as obtained by the QCDSF-UKQCD group are recovered. We
predict the pion- and strangeness sigma terms and the pion-mass dependence of
the octet and decuplet ground states at different strange quark masses.Comment: 15 pages, 5 tables, 3 figures. There are two significant extensions
in the revised manuscript. First, a precise determination of the axial
coupling constants F and D from the lattice data on the baryon masses is
provided. Second, it is shown that the lattice data of the QCDSF-UKQCD group
on the baryon masses in the flavor symmetric limit are recovered. The 3rd
version is the published versio
On the consistency of recent QCD lattice data of the baryon ground-state masses
In our recent analysis of lattice data of the BMW, LHPC and PACS-CS groups we
determined a parameter set of the chiral Lagrangian that allows a simultaneous
description of the baryon octet and decuplet masses as measured by those
lattice groups. The results on the baryon spectrum of the HSC group were
recovered accurately without their inclusion into our 6 parameter fit. We show
that the same parameter set provides an accurate reproduction of the recent
results of the QCDSF-UKQCD group probing the baryon masses at quite different
quark masses. This shows a remarkable consistency amongst the different lattice
simulations. With even more accurate lattice data in the near future it will
become feasible to determine all low-energy parameters relevant at NLO.Comment: 7 pages, 2 figure
UAT ADS-B Data Anomalies and the Effect of Flight Parameters on Dropout Occurrences
An analysis of the performance of automatic dependent surveillance-broadcast (ADS-B) data received from the Grand Forks, North Dakota International Airport was carried out in this study. The purpose was to understand the vulnerabilities of the universal access transceiver (UAT) ADS-B system and recognize the effects on present and future air traffic control (ATC) operation. The Federal Aviation Administration (FAA) mandated all the general aviation aircraft to be equipped with ADS-B. The aircraft flying within United States and below the transition altitude (18,000 feet) are more likely to install a UAT ADS-B. At present, unmanned aircraft systems (UAS) and autonomous air traffic control (ATC) towers are being integrated into the aviation industry and UAT ADS-B is a basic sensor for both class 1 and class 2 detect-and-avoid (DAA) systems. As a fundamental component of future surveillance systems, the anomalies and vulnerabilities of the ADS-B system need to be identified to enable a fully-utilized airspace with enhanced situational awareness. The data received was archived in GDL-90 format, which was parsed into readable data. The anomaly detection of ADS-B messages was based on the FAA ADS-B performance assessment report. The data investigation revealed ADS-B message suffered from different anomalies including dropout, missing payload, data jump, low confidence data, and altitude discrepancy. Among those studied, the most severe was dropout and 32.49% of messages suffered from this anomaly. Dropout is an incident where ADS-B failed to update within a specified rate. Considering the potential danger being imposed, an in-depth analysis was carried out to characterize message dropout. Three flight parameters were selected to investigate their effect on dropout. Statistical analysis was carried out and the Friedman Statistical Test identified that altitude affected dropout more than any other flight parameter
Nuclear thermodynamics and the in-medium chiral condensate
The temperature dependence of the chiral condensate in isospin-symmetric
nuclear matter at varying baryon density is investigated using thermal
in-medium chiral effective field theory. This framework provides a realistic
approach to the thermodynamics of the correlated nuclear many-body system and
permits calculating systematically the pion-mass dependence of the free energy
per particle. One- and two-pion exchange processes, -isobar
excitations, Pauli blocking corrections and three-body correlations are treated
up to and including three loops in the expansion of the free energy density. It
is found that nuclear matter remains in the Nambu-Goldstone phase with
spontaneously broken chiral symmetry in the temperature range MeV and at baryon densities at least up to about twice the density of
normal nuclear matter, fm. Effects of the nuclear
liquid-gas phase transition on the chiral condensate at low temperatures are
also discussed.Comment: 9 pages, 4 figures. arXiv admin note: substantial text overlap with
arXiv:1104.281
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