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 $U_A(1)$-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 $U_A(1)$-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 $U_A(1)$-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.

Strong Two--Body Decays of Light Mesons

In this paper, we present results on strong two-body decay widths of light $q\bar q$ mesons calculated in a covariant quark model. The model is based on the Bethe-Salpeter equation in its instantaneous approximation and has already been used for computing the complete meson mass spectrum and many electroweak decay observables. Our approach relies on the use of a phenomenological confinement potential with an appropriate spinorial Dirac structure and 't Hooft's instanton--induced interaction as a residual force for pseudoscalar and scalar mesons. The transition matrix element for the decay of one initial meson into two final mesons is evaluated in lowest order by considering conventional decays via quark loops as well as Zweig rule violating instanton--induced decays generated by the six--quark vertex of 't Hooft's interaction; the latter mechanism only contributes if all mesons in the decay have zero total angular momentum. We show that the interference of both decay mechanisms plays an important role in the description of the partial widths of scalar and pseudoscalar mesons.Comment: 35 pages, 7 figure

Use of Policy Risk Assessment Results in Political Decision Making

The RAPID project established, during the first period, a thematic network of risk assessment experts, including relevant partners in the ten countries involved, the "Risk assessor database". The project devoted a specific activity, a single work package, to the dissemination and discussion of the methodology developed during" first two years of the project. National workshops were planned in each country to facilitate integrated knowledge translation activity, using a participatory approach to increase potential knowledge-users awareness on the RAPID project, and to engage them in using the RAPID guidance. Workshops were conceived to present case studies and the RAPID guidance to a targeted audience, to discuss and collect further insights, and integrate different perspectives in the final version of the policy evaluation methodology. However, national workshops also actively contributed to develop evidence based methodological guidance and increase its quality and relevance for potential users by bridging know-do gap between researchers and stakeholders; by involving decision makers and potential users in the knowledge creation process; by facilitating diverse stakeholder participation from governmental, academic and private sectors, carefully identified by national RAPID surveys as having direct expertise in the field of risk assessment. The cultural and administrative differences existing in the countries involved in RAPID guarantee the inclusion of a wide range of perspectives. Results of the national workshops helped to identify barriers and solutions for using the guidance, for adapting necessary changes to it and for communicating results to other potential users.

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

Public Health, Policy Analysis, Risk Assessment,and Impact Assessment

Public health has been defined as "the science and art of preventing disease, prolonging life and promoting health through the organized efforts and informed choices of society, organizations, public and private, communities and individuals"(Winslow 1920) or as "the art of applying science in the context of politics so as to reduce inequalities in health while ensuring the best health for the greatest number"(WHO1998). As the challenges of public health have evolved, from sanitary surveillance and infectious diseases in the past, to chronic diseases, lifestyle factors,socioeconomic conditions, occupational and environmental health determinants,health reforms and others, so have the methods of assessment advanced by research technologies development. The new health threats and epidemics, such as AIDS, SARS (Severe Acute Respiratory Syndrome), influenza H5N1, or emergencies like natural disasters or bioterrorism, effects of globalization and migration present new tasks to public health governance requiring new working methods.