304 research outputs found
Study of the Interaction Close to the and Thresholds
The interaction close to the threshold is considered.
Specifically, the pronounced structure seen in production reactions like and around the threshold
is analyzed. Modern interaction models of the coupled
systems generate such a structure either due to the presence of a
(deuteron-like) unstable bound state or of an inelastic virtual state. % A
determination of the position of the prominent peak as observed in various
experiments for the two aforementioned reactions leads to values that agree
quite well with each other. Furthermore, the deduced mean value of MeV for the peak position coincides practically with the threshold energy
of the channel. This supports the interpretation of the structure
as a genuine cusp, signaling an inelastic virtual state in the
partial wave of the isospin 1/2 channel. % There is also evidence
for a second peak (or shoulder) in the data sets considered which appears at
roughly 10-15 MeV above the threshold. However, its concrete
position varies significantly from data set to data set and, thus, a
theoretical interpretation is difficult.Comment: accepted for publication Nucl. Phys.
Event Reconstruction for a DIRC
Monte Carlo simulations were made for a possible DIRC at the WASA detector at
COSY. A statistical method for pattern recognition is presented and the
possible angle resolution and velocity precision achieved are discussed.Comment: Minor changes in text. Figures updated. accepted by JINS
Polarization phenomena in the reaction NN to NNpi near threshold
First calculations for spin-dependent observables of the reactions , and near threshold are presented,
employing the J\"ulich model for pion production. The influence of resonant
(via the excitation of the ) and non-resonant p-wave pion
production mechanisms on these observables is examined. For the reactions and nice agreement of our predictions with the
presently available data on spin correlation coefficents is observed whereas
for the description of the data is less satisfying.Comment: 10 pages, 4 figure
Isotopic Production Cross Sections in Proton-Nucleus Collisions at 200 MeV
Intermediate mass fragments (IMF) from the interaction of Al,
Co and Au with 200 MeV protons were measured in an angular range
from 20 degree to 120 degree in the laboratory system. The fragments, ranging
from isotopes of helium up to isotopes of carbon, were isotopically resolved.
Double differential cross sections, energy differential cross sections and
total cross sections were extracted.Comment: accepted by Phys. Rev.
Fission studies with 140 MeV -Particles
Binary fission induced by 140 MeV -particles has been measured for
Ag, La, Ho and Au targets. The measured
quantities are the total kinetic energies, fragment masses, and fission cross
sections. The results are compared with other data and systematics. A minimum
of the fission probability in the vicinity is observed.Comment: 4 figures, 2 table
Search for Low Mass Exotic mesonic structures. Part I: experimental results
Recently, several papers discussed on the existence of a low mass new
structure at a mass close to M=214.3 MeV. It was suggested that the
disintegration: pP, P
proceeds through an intermediate particle P having such mass. The present
work intends to look at other new or available data, in order to observe the
eventual existence of small narrow peaks or shoulders in very low mesonic
masses. Indeed narrow structures were already extracted from various data in
dibaryons, baryons and mesons (at larger masses that those studied here).Comment: 7 pages 11 figure
Study of the and reactions close to threshold
Two--kaon production in proton--deuteron collisions has been studied at three
energies close to threshold using a calibrated magnetic spectrograph to measure
the final He and a vertex detector to measure the pair.
Differential and total cross sections are presented for the production of
--mesons, decaying through , as well as for prompt
production. The prompt production seems to follow phase space in both
its differential distributions and in its energy dependence. The amplitude for
the {He} reaction varies little for excess energies below 22
MeV and the value is consistent with that obtained from a threshold
measurement. The angular distribution of the decay pair shows that
near threshold the --mesons are dominantly produced with polarization
along the initial proton direction. No conclusive evidence for
production is found in the data.Comment: 13 figure
Upper limits for a narrow resonance in the reaction p + p -> K^+ + (Lambda p)
The reaction pp -> K^+ + (Lambda p) has been measured at T_p = 1.953 GeV and
\Theta = 0 deg with a high missing mass resolution in order to study the Lambda
p final state interaction. Narrow S = -1 resonances predicted by bag model
calculations are not visible in the missing mass spectrum. Small structures
observed in a previous experiment are not confirmed. Upper limits for the
production cross section of a narrow resonance are deduced for missing masses
between 2058 and 2105 MeV/c^2.Comment: 8 pages, 5 figure
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