Speaker
Annika Thiel
(University of Bonn)
Description
In order to understand the dynamics inside the nucleons, their excitation spectrum
needs to be measured and compared to theoretical models like constituent quark models
or recent lattice calculations. Since the excitation spectrum consists of several strongly
overlapping resonances, these resonances are difficult to disentangle and identify. To
determine their exact contributions, a solution of the partial wave analysis has to be
found. For an exact determination of the amplitudes, measurements of several single
and double polarization observables in various final states are needed.
With the CBELSA/TAPS experiment, measurements have been performed to determine
single and double polarization parameters in meson photoproduction. Unpolarized or
longitudinally polarized electrons are provided by the accelerator ELSA, which allow
either unpolarized, circularly or linearly polarized photon beams. For the measurement
of double polarization data, a butanol target provides longitudinally or transversely
polarized nucleons. The CBELSA/TAPS setup features a nearly full 4$\pi$ angular coverage
and a high detection efficiency for neutral photons, which gives an ideal condition for
the study of final states comprising neutral mesons.
This talk will show how the polarization degree of the photons and the dilution factor of
the butanol target are determined. Additionally, the new results of different polarization
observables for single meson photoproduction will be shown.
Supported by the DFG (SFB/TR16).
Primary author
Annika Thiel
(University of Bonn)
