997 research outputs found
The Meson Spectrum in a Covariant Quark Model
Within the framework of the instantaneous Bethe-Salpeter equation, we present
a detailed analysis of light meson spectra with respect to various
parameterizations of confinement in Dirac space. Assuming a linearly rising
quark-antiquark potential, we investigate two different spinorial forms (Dirac
structures), namely {1/2}(\Id\otimes\Id - \gamma^0\otimes\gamma^0) as well as
the -invariant combination {1/2}(\Id\otimes\Id -
\gamma^5\otimes\gamma^5 - \gamma^\mu\otimes\gamma_\mu), both providing a good
description of the ground state Regge trajectories up to highest observed
angular momenta. Whereas the first structure is slightly prefered concerning
numerous meson decay properties (see \cite{pap41}), we find the
-invariant force to be much more appropriate for the description of a
multitude of higher mass resonances discovered in the data of the {\sc Crystal
Barrel} collaboration during the last few years. Furthermore, this confinement
structure has the remarkable feature to yield a linear dependence of masses on
their radial excitation number. For many experimental resonances such a
trajectory-like behaviour was observed by Anisovich {\it et al.} We can confirm
that almost the same slope occurs for all trajectories. Adding the
-breaking instanton induced 't Hooft interaction we can compute the
pseudoscalar mass splittings with both Dirac structures and for the scalar
mesons a natural mechanism of flavour mixing is achieved. [...]Comment: 32 pages including 19 figures and 3 tables; submitted to Eur. Phys.
Different Roughness Length Scales in Water Worked Sediment Deposits and Their Effect on the Near Bed Turbulent Flow Field
Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv
Semileptonic decays of baryons in a relativistic quark model
We calculate semileptonic decays of light and heavy baryons in a
relativistically covariant constituent quark model. The model is based on the
Bethe-Salpeter-equation in instantaneous approximation. It generates
satisfactory mass spectra for mesons and baryons up to the highest observable
energies. Without introducing additional free parameters we compute on this
basis helicity amplitudes of electronic and muonic semileptonic decays of
baryons. We thus obtain form factor ratios and decay rates in good agreement
with experiment.Comment: 8 pages, 10 figures, 2 tables, typos remove
Dual character of the electronic structure in YBa2Cu4O8: conduction bands of CuO2 planes and CuO chains
We use microprobe Angle-Resolved Photoemission Spectroscopy (muARPES) to
separately investigate the electronic properties of CuO2 planes and CuO chains
in the high temperature superconductor, YBa2Cu4O8. In the CuO2 planes, a two
dimensional (2D) electronic structure with nearly momentum independent bilayer
splitting is observed. The splitting energy is 150 meV at (pi,0), almost 50%
larger than in Bi2Sr2CaCu2O(8+d) and the electron scattering at the Fermi level
in the bonding band is about 1.5 times stronger than in the antibonding band.
The CuO chains have a quasi one dimensional (1D) electronic structure. We
observe two 1D bands separated by ~ 550meV: a conducting band and an insulating
band with an energy gap of ~ 240meV. We find that the conduction electrons are
well confined within the planes and chains with a non-trivial hybridization.Comment: 4 pages, 4 figure
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