Data on the polarization observables T, P, and H for the reaction γp→pπ0 are reported. Compared to earlier data from other experiments, our data are more precise and extend the covered range in ...energy and angle substantially. The results were extracted from azimuthal asymmetries measured using a transversely polarized target and linearly polarized photons. The data were taken at the Bonn electron stretcher accelerator ELSA with the CBELSA/TAPS detector. Within the Bonn-Gatchina partial wave analysis, the new polarization data lead to a significant narrowing of the error band for the multipoles for neutral-pion photoproduction.
The photoproduction of 2
π
0
mesons off protons was studied with the Crystal Barrel/TAPS experiment at the electron accelerator ELSA in Bonn. The energy of photons produced in a radiator was tagged ...in the energy range from 600 MeV to 2.5 GeV. Differential and total cross sections and
pπ
0
π
0
Dalitz plots are presented. Part of the data was taken with a diamond radiator producing linearly polarized photons, and beam asymmetries were derived. Properties of nucleon and
Δ
resonances contributing to the
pπ
0
π
0
final state were determined within the Bonn-Gatchina (BnGa) partial-wave analysis. The data presented here allow us to determine branching ratios of nucleon and
Δ
resonances for their decays into
pπ
0
π
0
via several intermediate states. Most prominent are decays proceeding via
Δ
(1232)
π
,
N
(1440)1/2
+
π
,
N
(1520)3/2
−
π
,
N
(1680)5/2
+
π
, but also
pf
0
(500),
pf
0
(980), and
pf
2
(1270) contribute to the reaction.
Photoproduction of η -mesons off protons Bartholomy, O.; Bogendörfer, R.; Credé, V. ...
The European physical journal. A, Hadrons and nuclei,
8/2007, Letnik:
33, Številka:
2
Journal Article
The photoproduction of η -mesons off
12
C ,
40
Ca ,
93
Nb , and
nat
Pb nuclei has been measured with a tagged photon beam with energies between 0.6 and 2.2GeV. The experiment was performed at the ...Bonn ELSA accelerator with the combined setup of the Crystal Barrel and TAPS calorimeters. It aimed at the in-medium properties of the
S
11
(1535) nucleon resonance and the study of the absorption properties of nuclear matter for η -mesons. Careful consideration was given to contributions from ηπ final states and secondary production mechanisms of η -mesons,
e.g.
from inelastic π
N
reactions of intermediate pions. The analysis of the mass number scaling shows that the nuclear absorption cross-section
for η -mesons is constant over a wide range of the η momentum. The comparison of the excitation functions to data off the deuteron and to calculations in the framework of a BUU model show no unexplained in-medium modifications of the
S
11
(1535) .
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