387 research outputs found
The pi-N Sigma term - a lattice investigation
A lattice calculation of the pi-N sigma term is described using dynamical
staggered fermions. Preliminary results give a sea term comparable in magnitude
to the valence term.Comment: Latex article. 6 pages, uuencoded compressed tar file. Contribution
to the Kyffhaeuser Workshop (Leipzig, Germany, September 1993). HLRZ preprint
93-6
The ``Spin'' Structure of the Nucleon - a lattice investigation
We will discuss here an indirect lattice evaluation of the baryon axial
singlet current matrix element. This quantity may be related to the fraction of
nucleon spin carried by the quarks. The appropriate structure function has
recently been measured (EMC experiment). As in this experiment, we find that
the quarks do not appear to carry a large component of the nucleon spin.Comment: Latex article. 3 pages. Contribution to the Second IMACS Conference
on Computational Physics, Cahokia, U.S.A. October 1993. HLRZ preprint 93-7
The pi-N Sigma term - an evaluation using staggered fermions
A lattice calculation of the pi-N sigma term is described using dynamical
staggered fermions. Preliminary results give a sea term comparable in magnitude
to the valence term.Comment: Latex article, 3 pages. Contribution to the LAT93 Conference (Dallas,
U.S.A., September 1993). HLRZ preprint 93-7
Hadronic coupling constants in lattice QCD
We report on calculations of the hadronic coupling constants
and based on lattice QCD with four flavors of dynamical staggered
fermions. By computing 2--point and 3--point Green's functions we have been
able to determine these coupling constants ab initio from QCD; the results are
compatible with the experimental values.Comment: 3 Page
The spin content of the proton in full QCD
We present preliminary results on the proton spin structure function in full
QCD. The measurement has been done using 4 flavours of staggered fermions and
an improved definition of the lattice topological charge density.Comment: 3 pages, 3 figures, contribution to Lattice-97. Latex file including
espcrc2.sty. The colour of a line in the first figure has been changed to
avoid problems on some printer
Hadronic Coupling Constants in Lattice QCD
We calculate the hadronic coupling constants and
in QCD, including dynamical quarks in the framework of staggered fermions in
the lattice approach. For the nucleon--pion coupling we obtain , to be compared with the experimental value . The
coupling has been analysed for two different sets of operators
with the averaged result which is to be compared
with the experimental value .Comment: 14 pages uuencoded postscript fil
MULTIDIMENSIONAL PEPTIDE/PROTEIN ANALYSIS AND IDENTIFICATION BY SEQUENCE DATABASE SEARCH USING MASS SPECTROMETRIC DATA
In order to generate proteomics data that are suitable to validate protein identification in complex mixtures using multidimensional liquid-chromatography-mass spectrometry approaches, we implemented an offline two-dimensional liquid chromatography method combining strong cation-exchange- and ion-pair reversed-phase chromatography followed by electrospray ionization tandem mass spectrormetry (ESI-MS/MS) for the analysis of a bovine serum albumin digest. The fragment ion spectra generated by ESI-MS/MS were subsequently analyzed via MASCOT database search. The obtained identification data were evaluated in terms of quality of protein/peptide identification by means of score values, reproducibility of identification in replicate measurements, distribution of tryptic peptides among different fractions, and overall number of unique identified proteins/peptides.
Finally, we improved the trapping conditions in the second dimension by using a more hydrophobic amphiphile in the loading buffer. The improvement was demonstrated by comparison of the obtained identification data, such as number of identified peptides, cumulative mowse scores and reproducibility of identification
Helicity and alpha-effect by current-driven instabilities of helical magnetic fields
Helical magnetic background fields with adjustable pitch angle are imposed on
a conducting fluid in a differentially rotating cylindrical container. The
small-scale kinetic and current helicities are calculated for various field
geometries, and shown to have the opposite sign as the helicity of the
large-scale field. These helicities and also the corresponding -effect
scale with the current helicity of the background field. The -tensor is
highly anisotropic as the components and have
opposite signs. The amplitudes of the azimuthal -effect computed with
the cylindrical 3D MHD code are so small that the operation of an
dynamo on the basis of the current-driven, kink-type
instabilities of toroidal fields is highly questionable. In any case the low
value of the -effect would lead to very long growth times of a dynamo
in the radiation zone of the Sun and early-type stars of the order of
mega-years.Comment: 6 pages, 7 figures, submitted to MNRA
The Spin Content of the Nucleon
The fraction of the nucleon spin that is carried by the quarks, , is computed in lattice QCD with dynamical staggered fermions. We
obtain the value .Comment: (contribution to Lattice 1992), 4 pages + 1 encapsulated postscript
figure, HLRZ 92-81 (In the earlier version the topological charge density was
incorrectly normalized. ERRARE HUMANUM EST!
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