10 research outputs found
Meson Production on the Nucleon in the Giessen K-Matrix Approach
Meson production on the proton is described in a coupled channels K-matrix
approach. Both hadronic and photonic scenarios are taken into account on the
same theoretical footing. At tree-level the Born amplitudes are obtained from
an effective Lagrangian with phenomenologically adjustable coupling constants.
The spectral distributions, resonances and their width and the background
contributions are obtained within the same approach, thus accounting properly
for interference effects. Applications to omega- and associated strangeness
production on the proton are discussed.Comment: 11 pages, 6 Figures, Proc. Int. Workshop NSTAR 2005 at Tallahassee,
Fl., Oct. 200
production in the Giessen coupled-channel model
We present a coupled-channel Lagrangian approach (GiM) to describe the , scattering in the resonance energy region. The
production has been significantly improved by using the isobar approximation
with and in the intermediate state. The
three-body unitarity is maintained up to interference pattern between the
isobar subchannels. The scattering amplitudes are obtained as a solution of the
Bethe-Salpeter equation in the matrix approximation. As a first application
we perform a partial wave analysis of the ,
reactions in the Roper resonance region. We obtain \,\% and \,\% for the
and decay branching ratios of respectively.
The extracted inelasticities and reaction amplitudes are consistent
with the results from other groups.Comment: replaced with the published versio
Eta-meson production in the resonance energy region
We perform an updated coupled-channel analysis of eta-meson production
including all recent photoproduction data on the proton. The dip observed in
the differential cross sections at c.m. energies W=1.68 GeV is explained by
destructive interference between the and states.
The effect from is found to be small but still important to
reproduce the correct shape of the differential cross section.
For the scattering we suggest a reaction mechanism in
terms of the , , and states. Our
conclusion on the importance of the , , and
resonances in the eta-production reactions is in line with our
previous results. No strong indication for a narrow state with a width of 15
MeV and the mass of 1680 MeV is found in the analysis. scattering
length is extracted and discussed.Comment: replaced with a published version, pole parameters and scattering
lengths are adde
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
Study of nucleon resonances with electromagnetic interactions
Recent developments in using electromagnetic meson production reactions to
study the structure of nucleon resonances are reviewed. Possible future works
are discussed.Comment: 25 pages, 19 figure