344 research outputs found
Radiative Decay of Vector Quarkonium: Constraints on Glueballs and Light Gluinos
Given a resonance of known mass, width, and J^{PC}, we can determine its
gluonic branching fraction, b(R->gg), from data on its production in radiative
vector quarkonium decay, V -> gamma+R. For most resonances b(R->gg) is found to
be O(10%), consistent with being q-qbar states, but we find that both
pseudoscalars observed in the 1440 MeV region have b(R->gg) ~ 1/2 - 1, and
b(f_0^{++}->gg) ~ 1/2. As data improves, b(R->gg) should be a useful
discriminator between q-qbar and gluonic states and may permit quantitative
determination of the extent to which a particular resonance is a mixture of
glueball and q-qbar. We also examine the regime of validity of pQCD for
predicting the rate of V -> gamma+eta_gluino, the ``extra'' pseudoscalar bound
state which would exist if there were light gluinos. From the CUSB limit on
peaks in Upsilon -> gamma X, the mass range 3 GeV < m(eta_gluino) < 7 GeV can
be excluded. An experiment must be significantly more sensitive to exclude an
eta_gluino lighter than this.Comment: 36pp (inc figs),RU-94-04. (Replaces original which didn't latex
correctly and didn't have figures.
Meson Decay Constants from Isospin Mass Splittings in the Quark Model
Decay constants of and mesons are estimated within the framework of a
heavy-quark approach using measured isospin mass splittings in the , ,
and states to isolate the electromagnetic hyperfine interaction between
quarks. The values MeV and MeV are
obtained. Only experimental errors are given; possible theoretical ambiguities,
and suggestions for reducing them, are noted.Comment: 7 pages, LaTeX, EFI-92-3
Acute coronary ischemia during alcohol withdrawal: a case report
<p>Abstract</p> <p>Introduction</p> <p>The potential of alcohol withdrawal to cause acute coronary events is an area that needs the urgent attention of clinicians and researchers.</p> <p>Case presentation</p> <p>We report the case of a 52-year-old heavy-alcohol-using Sri Lankan man who developed electocardiogram changes suggestive of an acute coronary event during alcohol withdrawal. Despite the patient being asymptomatic, subsequent echocardiogram showed evidence of ischemic myocardial dysfunction. We review the literature on precipitation of myocardial ischemia during alcohol withdrawal and propose possible mechanisms.</p> <p>Conclusions</p> <p>Alcohol withdrawal is a commonly observed phenomenon in hospitals. However, the number of cases reported in the literature of acute coronary events occurring during withdrawal is few. Many cases of acute ischemia or sudden cardiac deaths may be attributed to other well known complications of delirium tremens. This is an area needing the urgent attention of clinicians and epidemiologists.</p
Deep inelastic production at HERA in the -factorization approach and its consequences for the nonrelativistic QCD
In the framework of the -factorization approach, we analyse the
inclusive and inelastic production of particles in deep inelastic
scattering. We take into account both colour-singlet and colour-octet
production channels. We inspect the sensitivity of theoretical predictions to
the choice of model parameters. Our theoretical results agree reasonably well
with recent experimental data collected by the collaboration H1 at HERA.Comment: 14 pages, 6 figure
Wissenschaftliche Monitoringkonzepte für die Deutsche Bucht (WIMO) - Abschlussbericht
The state and development of coastal marine systems and an understanding of the interaction of
organisms, sea floor, water column, and biochemical and physical processes can only be obtained by
a combination of long-term monitoring and modelling approaches of different complexity. A need for the development and evaluation of monitoring strategies is driven by a framework of different
European and German regulations. The research project WIMO (Scientific Monitoring Concepts for the German Bight) has developed concepts and methods that aim at a fundamental scientific understanding of marine systems and also meet monitoring requirements of European legislation and regulations like the EU Marine Strategy Framework Directive. In this final report examples of common descriptors of ecosystem state like seabed integrity, eutrophication, and biodiversity are discussed. It has been assessed to what extent established measuring procedures used to survey the characteristics of the sea floor, and newly developed technologies are eligible for governmental monitoring. The significance of integrative modelling for linking and visualising results of measurements and
models is illustrated. It is shown how new concepts have been implemented into governmental monitoring in the form of web based data sheets. These insights enable continuous analyses and developments in the future
Leptonic and Semileptonic Decays of Charm and Bottom Hadrons
We review the experimental measurements and theoretical descriptions of
leptonic and semileptonic decays of particles containing a single heavy quark,
either charm or bottom. Measurements of bottom semileptonic decays are used to
determine the magnitudes of two fundamental parameters of the standard model,
the Cabibbo-Kobayashi-Maskawa matrix elements and . These
parameters are connected with the physics of quark flavor and mass, and they
have important implications for the breakdown of CP symmetry. To extract
precise values of and from measurements, however,
requires a good understanding of the decay dynamics. Measurements of both charm
and bottom decay distributions provide information on the interactions
governing these processes. The underlying weak transition in each case is
relatively simple, but the strong interactions that bind the quarks into
hadrons introduce complications. We also discuss new theoretical approaches,
especially heavy-quark effective theory and lattice QCD, which are providing
insights and predictions now being tested by experiment. An international
effort at many laboratories will rapidly advance knowledge of this physics
during the next decade.Comment: This review article will be published in Reviews of Modern Physics in
the fall, 1995. This file contains only the abstract and the table of
contents. The full 168-page document including 47 figures is available at
http://charm.physics.ucsb.edu/papers/slrevtex.p
Upsilonium polarization as a touchstone in understanding the proton dynamics in QCD
In the framework of the k_t-factorization approach, the production of
\alpha$ are presented. We argue
that measuring the polarization of quarkonium states can serve as a crucial
test discriminating two competing theoretical approaches to parton dynamics in
QCD.Comment: 8 pages, 2 figure
Possible Explanation Why \tau_{B^{\pm}}\sim\tau_{B^0} But \tau_{D^{\pm}}\sim \tau_{D^0}
Data show that \tau_{B^{\pm}}\sim\tau_{B^0}, but \tau_{D^{\pm}}\sim
2\tau_{D^0}. The naive interpretation which attributes \tau_{D^{\pm}}\sim
2\tau_{D^0} to a destructive interference between two quark diagrams for
D^{\pm} decays, definitely fails in the B-case. We investigate Close and
Lipkin's suggestion that the phases for producing radially excited states
\psi_{2s} in the decay products of B-mesons can possess an opposite sign to the
integrals for \psi_{1s} decay products. Their contributions can partially
compensate each other to result in \tau_{B^{\pm}}\sim\tau_{B^0}. Since D-mesons
are much lighter than B-mesons, such possibilities do not exist in D-decays.Comment: 14 pages, latex, 4 ps figures. to appear in Phys. Rev.
The Coastal Observing System for Northern and Arctic Seas (COSYNA)
The Coastal Observing System for Northern and Arctic Seas (COSYNA) was established in order to better understand the complex interdisciplinary processes of northern seas and the Arctic coasts in a changing environment. Particular focus is given to the German Bight in the North Sea as a prime example of a heavily used coastal area, and Svalbard as an example of an Arctic coast that is under strong pressure
due to global change. The COSYNA automated observing and modelling system is designed to monitor real-time conditions and provide short-term forecasts, data, and data products to help assess the impact of anthropogenically induced change. Observations are carried out by combining satellite and radar remote sensing with various in situ platforms. Novel sensors, instruments, and algorithms are developed to further improve the understanding of the interdisciplinary interactions between physics, biogeochemistry, and the ecology of coastal seas. New modelling and data assimilation techniques are used to integrate observations and models in a quasi-operational system providing descriptions and forecasts of key hydrographic variables. Data and data products are publicly available free of charge and in real time. They are used by multiple interest
groups in science, agencies, politics, industry, and the public
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