53,094 research outputs found
Hadron Spectroscopy with COMPASS at CERN
The aim of the COMPASS hadron programme is to study the light-quark hadron
spectrum, and in particular, to search for evidence of hybrids and glueballs.
COMPASS is a fixed-target experiment at the CERN SPS and features a two-stage
spectrometer with high momentum resolution, large acceptance, particle
identification and calorimetry. A short pilot run in 2004 resulted in the
observation of a spin-exotic state with consistent with the
debated . In addition, Coulomb production at low momentum transfer
data provide a test of Chiral Perturbation Theory. During 2008 and 2009, a
world leading data set was collected with hadron beam which is currently being
analysed. The large statistics allows for a thorough decomposition of the data
into partial waves. The COMPASS hadron data span over a broad range of channels
and shed light on several different aspects of QCD.Comment: 4 pages, 5 figure
The Chinese-French SVOM mission for Gamma-Ray Burst studies
We present the Space-based multi-band astronomical Variable Objects Monitor
mission (SVOM) decided by the Chinese National Space Agency (CNSA) and the
French Space Agency (CNES). The mission which is designed to detect about 80
Gamma-Ray Bursts (GRBs) of all known types per year, will carry a very
innovative scientific payload combining a gamma-ray coded mask imagers
sensitive in the range 4 keV to 250 keV, a soft X-ray telescope operating
between 0.5 to 2 keV, a gamma-ray spectro-photometer sensitive in the range 50
keV to 5 MeV, and an optical telescope able to measure the GRB afterglow
emission down to a magnitude limit M with a 300 s exposure. A particular
attention will be also paid to the follow-up in making easy the observation of
the SVOM detected GRB by the largest ground based telescopes.
Scheduled for a launch in 2013, it will provide fast and reliable GRB
positions, will measure the broadband spectral energy distribution and temporal
properties of the prompt emission, and will quickly identify the optical
afterglows of detected GRBs, including those at very high redshift.Comment: Proceedings of the SF2A conference, Paris, 200
Operational Trans-Resistance Amplifier Based Tunable Wave Active Filter
In this paper, Operational Trans-Resistance Amplifier (OTRA) based wave active filter structures are presented. They are flexible and modular, making them suitable to implement higher order filters. The circuits implement the resistors using matched transistors, operating in linear region, making them well suited for IC fabrication. They are insensitive to parasitic input capacitances and input resistances due to the internally grounded input terminals of OTRA. As an application, a doubly terminated third order Butterworth low pass filter has been implemented, by substituting OTRA based wave equivalents of passive elements. PSPICE simulations are given to verify the theoretical analysis
Making Cold Molecules by Time-dependent Feshbach Resonances
Pairs of trapped atoms can be associated to make a diatomic molecule using a
time dependent magnetic field to ramp the energy of a scattering resonance
state from above to below the scattering threshold. A relatively simple model,
parameterized in terms of the background scattering length and resonance width
and magnetic moment, can be used to predict conversion probabilities from atoms
to molecules. The model and its Landau-Zener interpretation are described and
illustrated by specific calculations for Na, Rb, and Cs
resonances. The model can be readily adapted to Bose-Einstein condensates.
Comparison with full many-body calculations for the condensate case show that
the model is very useful for making simple estimates of molecule conversion
efficiencies.Comment: 11 pages, 11 figures; talk for Quantum Challenges Symposium, Warsaw,
Poland, September 4-7, 2003. Published in Journal of Modern Optics 51,
1787-1806 (2004). Typographical errors in Journal article correcte
Ionization of hydrogen atoms by electron impact at 1eV, 0.5eV and 0.3eV above threshold
We present here triple differential cross sections for ionization of hydrogen
atoms by electron impact at 1eV, 0.5eV and 0.3eV energy above threshold,
calculated in the hyperspherical partial wave theory. The results are in very
good agreement with the available semiclassical results of Deb and Crothers
\cite{DC02} for these energies. With this, we are able to demonstrate that the
hyperspherical partial wave theory yields good cross sections from 30 eV
\cite{DPC03} down to near threshold for equal energy sharing kinematics.Comment: 6 pages, 9 figure
Sensitivity of the r-process to nuclear masses
The rapid neutron capture process (r-process) is thought to be responsible
for the creation of more than half of all elements beyond iron. The scientific
challenges to understanding the origin of the heavy elements beyond iron lie in
both the uncertainties associated with astrophysical conditions that are needed
to allow an r-process to occur and a vast lack of knowledge about the
properties of nuclei far from stability. There is great global competition to
access and measure the most exotic nuclei that existing facilities can reach,
while simultaneously building new, more powerful accelerators to make even more
exotic nuclei. This work is an attempt to determine the most crucial nuclear
masses to measure using an r-process simulation code and several mass models
(FRDM, Duflo-Zuker, and HFB-21). The most important nuclear masses to measure
are determined by the changes in the resulting r-process abundances. Nuclei
around the closed shells near N=50, 82, and 126 have the largest impact on
r-process abundances irrespective of the mass models used.Comment: 5 pages, 4 figures, accepted in European Physical Journal
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