The photoproduction of η′-mesons off different nuclei has been measured with the CBELSA/TAPS detector system for incident photon energies between 1500–2200 MeV. The transparency ratio has been ...deduced and compared to theoretical calculations describing the propagation of η′-mesons in nuclei. The comparison indicates a width of the η′-meson of the order of Γ=15–25 MeV at ρ=ρ0 for an average momentum pη′=1050 MeV/c, at which the η′-meson is produced in the nuclear rest frame. The inelastic η′N cross section is estimated to be 3–10 mb. Parameterizing the photoproduction cross section of η′-mesons by σ(A)=σ0Aα, a value of α=0.84±0.03 has been deduced.
Properties of the Roper resonance, the first scalar excitation of the nucleon, are determined. Pole positions and residues of the P11 partial wave are studied in a combined analysis of pion- and ...photo-induced reactions. We find the Roper pole at {(1371±7)−i(92±10)} MeV and an elasticity of 0.61±0.03. The largest decay coupling is found for the Nσ (σ=(ππ)-S-wave). The analysis is based on new data on γp→pπ0π0 for photons in the energy range from the two-pion threshold to 820 MeV from TAPS at Mainz and from 0.4 to 1.3 GeV from Crystal Barrel at Bonn and includes further data from other experiments. The partial wave analysis excludes the possibility that the Roper resonance is split into two states with different partial decay widths.
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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