18,781 research outputs found
Quark-gluon vertex dressing and meson masses beyond ladder-rainbow truncation
We include a generalized infinite class of quark-gluon vertex dressing
diagrams in a study of how dynamics beyond the ladder-rainbow truncation
influences the Bethe-Salpeter description of light quark pseudoscalar and
vector mesons. The diagrammatic specification of the vertex is mapped into a
corresponding specification of the Bethe-Salpeter kernel, which preserves
chiral symmetry. This study adopts the algebraic format afforded by the simple
interaction kernel used in previous work on this topic. The new feature of the
present work is that in every diagram summed for the vertex and the
corresponding Bethe-Salpeter kernel, each quark-gluon vertex is required to be
the self-consistent vertex solution. We also adopt from previous work the
effective accounting for the role of the explicitly non-Abelian three gluon
coupling in a global manner through one parameter determined from recent
lattice-QCD data for the vertex. With the more consistent vertex used here, the
error in ladder-rainbow truncation for vector mesons is never more than 10% as
the current quark mass is varied from the u/d region to the b region.Comment: 15 pages, 12 figure
Scalable iterative methods for sampling from massive Gaussian random vectors
Sampling from Gaussian Markov random fields (GMRFs), that is multivariate
Gaussian ran- dom vectors that are parameterised by the inverse of their
covariance matrix, is a fundamental problem in computational statistics. In
this paper, we show how we can exploit arbitrarily accu- rate approximations to
a GMRF to speed up Krylov subspace sampling methods. We also show that these
methods can be used when computing the normalising constant of a large
multivariate Gaussian distribution, which is needed for both any
likelihood-based inference method. The method we derive is also applicable to
other structured Gaussian random vectors and, in particu- lar, we show that
when the precision matrix is a perturbation of a (block) circulant matrix, it
is still possible to derive O(n log n) sampling schemes.Comment: 17 Pages, 4 Figure
Apparent multiple Delta m^2_32 in muon anti-neutrino and muon neutrino survival oscillations from non-standard interaction matter effect
Neutrinos propagating through matter may participate in forward coherent
neutral-current-like scattering arising from non-standard interactions as well
as from the Mikheyev-Smirnov-Wolfenstein matter potential . We show that
at fixed long baselines through matter of constant density, the non-standard
interaction potential can contribute an additional
term to the oscillation phase whose sign differs for \anumu versus \numu
propagation in matter. Its presence can cause different apparent
to be erroneously inferred on the basis of oscillations in vacuum, with values
lying above (for \anumu) or below (for \numu) the actual
for the case where is predominantly real-valued and of
sign opposite to . An NSI scenario invoking only
is shown to be capable of accounting for a disparity
recently reported between oscillation survival for \anumu and \numu fluxes
measured at by the MINOS experiment. Implications for mantle
traversal by atmospheric neutrinos are examined. The NSI matter potential with
non-maximal mixing could evade conventional atmospheric neutrino analyses which
do not distinguish \numu from \anumu on an event-by-event basis.Comment: 7 pages, 5 figures. Accepted for publication in Physical Review
Interplay of Spin and Orbital Angular Momentum in the Proton
We derive the consequences of the Myhrer-Thomas explanation of the proton
spin problem for the distribution of orbital angular momentum on the valence
and sea quarks. After QCD evolution these results are found to be in very good
agreement with both recent lattice QCD calculations and the experimental
constraints from Hermes and JLab
Experimental program for real gas flow code validation at NASA Ames Research Center
The experimental program for validating real gas hypersonic flow codes at NASA Ames Rsearch Center is described. Ground-based test facilities used include ballistic ranges, shock tubes and shock tunnels, arc jet facilities and heated-air hypersonic wind tunnels. Also included are large-scale computer systems for kinetic theory simulations and benchmark code solutions. Flight tests consist of the Aeroassist Flight Experiment, the Space Shuttle, Project Fire 2, and planetary probes such as Galileo, Pioneer Venus, and PAET
EFFECT OF RECREATIONAL TRAIL TRAFFIC LEVEL ON EASTERN RED-BACKED SALAMANDER (PLETHODON CINEREUS) RELATIVE ABUNDANCE
The effects of roads and trails on terrestrial salamanders, primarily plethodontids, can be important. The abundance of terrestrial salamanders often increases with distance from roads. Less is known about the effects of recreational or hiking trails on terrestrial salamanders than is known about the effects of roads. We explored how low and high traffic trails in a suburban biological reserve affect the relative abundance of Eastern Red-backed Salamanders (Plethodon cinereus). We found more salamanders under cover objects next to low traffic trails compared to either high traffic trails or wooded areas without trails. At wooded sites, we found only striped morphs whereas at high traffic sites we found only unstriped morphs. Low traffic sites included a range of color morph frequencies. The proportion of females found in each site did not differ, nor did the mean size of the salamanders. Our results suggest that the impact of recreational walking trails needs to be examined more closely to see how and why the distributions of P. cinereus, and potentially other woodland salamanders, are affected and what trail characteristics are important in driving the apparent effects. Such information will contribute to the design and maintenance of walking trails in natural areas that minimize effects on terrestrial salamanders, and likely other organisms
axial form factor from bubble chamber experiments
A careful reanalysis of both Argonne National Laboratory and Brookhaven
National Laboratory data for weak single pion production is done. We consider
deuteron nuclear effects and normalization (flux) uncertainties in both
experiments. We demonstrate that these two sets of data are in good agreement.
For the dipole parametrization of , we obtain , GeV. As an application we present the discussion of
the uncertainty of the neutral current 1 production cross section,
important for the T2K neutrino oscillation experiment.Comment: 16 pages, 8 figures, 2 table
Amino acid incorporation into mitochondrial ribosomes of Neurospora crassa wild-type and Mi-1 mutant
A proposed system for aviation noise measurement and control
January 1973Includes bibliographical references (p. 61-64)This report reviews previous work on various measures for aviation noise, and proposes a completely new system for aviation noise measurement and control compatible with real time, operational noise monitoring hardware. This new system allows new methods of control and regulation to be introduced and is designed to cover problems arising from future CTOL, RTOL, STOL, and VTOL aviation systems operating from current airports as well as new urban sites. New measures are proposed for aircraft flyover noise, airport noise exposure, and community noise impact
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