885 research outputs found
Three-body analysis of incoherent -photoproduction on the deuteron in the near threshold region
A three-body calculation of the reaction in the energy
region from threshold up to 30 MeV above has been performed. The primary goal
of this study is to assess the importance of the three-body aspects in the
hadronic sector of this reaction. Results are presented for the -meson
spectrum as well as for the total cross section. The three-body results differ
significantly from those predicted by a simple rescattering model in which only
first-order - and -interactions in the final state are considered.
The major features of the experimental data are well reproduced although right
at threshold the rather large total cross section could not be explained.Comment: 6 pages revtex including 3 figure
Coherent eta photoproduction on the deuteron in the resonance region
Coherent eta photoproduction on the deuteron is studied in the
resonance region neglecting eta rescattering and two-body processes. For the
elementary reaction on the nucleon, we have considered the dominant
resonance and as background the nucleon pole terms as well as
and meson exchange. We have studied the influence of different
choices for the neutron resonance amplitude, different prescriptions for fixing
the invariant mass of the resonance amplitude and different methods for
deriving the elementary production amplitude for an arbitrary reference frame.Comment: 33 pages revtex including 13 postscript figure
Coherent -photoproduction on He and C in the near-threshold region
Coherent meson photoproduction on He and C is considered in
the near-threshold region. The elementary photoproduction operator
includes contributions from the and resonances as
well as -channel vector meson exchange and the nucleon pole terms. Due to
the suppression of the dominant resonance for spin and isospin
saturated nuclei, the reaction is mainly governed by exchange.
Furthermore, the influence of Fermi motion and of different prescriptions for
the choice of the invariant reaction energy in the elementary
amplitude is studied.Comment: 27 pages revtex including 9 postscript figure
Breit - Wigner parameters of nucleon resonance S11(1535)
The result of partial - wave analysis of angular distributions for the
process gamma+p -> eta +p at the energies upto 2 GeV are given. From the energy
dependence of the regression coefficient a0(W) the reliable estimates of Breit
- Wigner parameters of S11(1535) - resonance and energy dependence of real and
imagenery parts of electric dipol amplitude E0+ and its phase were obtainedComment: 12 pages, 11 figure
eta-photoproduction in the resonance energy region
The production in the nucleon resonance energy region is studied
within the unitary coupled-channels effective Lagrangian approach of the
Giessen model. We demonstrate that the second peak recently observed in the
cross section of photoproduction on the neutron at =1.66 GeV
can be explained in terms of coupled-channel effects due to and
resonance excitations
The -system at low energy within a three-body approach
The role of the -interaction is studied in the low energy regime in
-deuteron reactions as well as in coherent and incoherent
-photoproduction on the deuteron using a three-body model with separable
two-body interactions. The three-body approach turns out to be quite essential
in the most important lowest partial wave. Results are presented for
differential and total cross sections as well as for the -meson spectrum.
They differ significantly from those predicted by a simple rescattering model
in which only first-order - and -interactions in the final state
are considered. The major features of the experimental data of
-photoproduction in the near-threshold region are well reproduced.Comment: 20 pages revtex including 10 figures, revised version accepted for
publication in Nucl. Phys.
Incoherent Photoproduction of -mesons from the Deuteron near Threshold
Incoherent photoproduction of the -meson on the deuteron is studied for
photon energies from threshold to 800 MeV. The dominant contribution, the
N-N amplitude, is described within an isobar model. The final
state interaction derived from the CD-Bonn potential is included and found to
be important for the description of the production cross section close to
threshold. Possible effects from the final state interaction are
discussed.Comment: 11 pages, revtex, including 6 figure
Do we understand the interaction from the near threshold photoproduction on the deuteron?
The effects of final state interaction in incoherent photoproduction
on deuteron are studied within a three-body approach including a realistic
potential. The results are compared with available data, and differences with
other theoretical predictions are analyzed. The role of the
interaction and the possibility of extracting the scattering
parameters from this reaction are discussed.Comment: 9 pages revtex including 6 ps-figure
Photoproduction of mesons off nuclei
Recent results for the photoproduction of mesons off nuclei are reviewed.
These experiments have been performed for two major lines of research related
to the properties of the strong interaction. The investigation of nucleon
resonances requires light nuclei as targets for the extraction of the isospin
composition of the electromagnetic excitations. This is done with quasi-free
meson photoproduction off the bound neutron and supplemented with the
measurement of coherent photoproduction reactions, serving as spin and/or
isospin filters. Furthermore, photoproduction from light and heavy nuclei is a
very efficient tool for the study of the interactions of mesons with nuclear
matter and the in-medium properties of hadrons. Experiments are currently
rapidly developing due to the combination of high quality tagged (and
polarized) photon beams with state-of-the-art 4pi detectors and polarized
targets
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