422 research outputs found
Meson Physics at Gem
Some experimental studies of production and interactions
performed or presently under way by the GEM collaboration at COSY J\"{u}lich
are reviewed.Comment: invited talk, ETA'05 Workshop, 15.- 17. Sept. 2005, Cracow, Polan
Physics at COSY
The COSY accelerator in J\'ulich is presented together with its internal and
external detectors. The physics programme performed recently is discussed with
emphasis on strangeness physics.Comment: Invited talk given at the "10th International Symposium on
Meson-Nucleon Physics and the Structure of the Nucleon (MENU04)," IHEP,
Beijing, China, 30/Aug.-4/Sept./0
Correlations of projectile like fragments in heavy ion reactions at Fermi energy
Correlations between pairs of projectile-like fragments, emitted by the
system at the laboratory bombarding energy of 515 MeV,
have been studied under two stipulated conditions: (1) at least one member of
the pair is emitted at an angle less than the grazing angle for the system, (2)
both the members of the pair are emitted at angles larger than the grazing
angle. A surprisingly large difference, by more than an order of magnitude, is
found between the correlations for the two cases. This observation could be
explained on the basis of a simple semi-classical break up model. Further
analysis of the variation of the charge correlation function with the
difference in the nuclear charges of the correlated pair showed trends which
are consistent with an "inelastic break up process", in which the projectile
breaks up at the radius of contact, in such a way that, one fragment
(preferably the lighter) is emitted to one side within the grazing angle, while
the other orbits around the target nucleus for a while and emerges on the other
side, at a negative scattering angle, much like in a deep inelastic scattering.Comment: 19 pages, 12 figures accepted by Eurp. Physics Journal
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
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
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
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
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.
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