Darmstadt 2016 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 33: Hadron Structure and Spectroscopy VI

HK 33.1: Gruppenbericht

Mittwoch, 16. März 2016, 14:00–14:30, S1/01 A5

Complete Experiments in pseudoscalar meson photoproduction — •Yannick Wunderlich for the CBELSA/TAPS collaboration — HISKP, Universität Bonn

The understanding of the nucleon excitation spectrum poses a long lasting challenge on the way towards a precise picture on how QCD forms bound states. Many excited states that were predicted by phenomenological models have not shown up in the results of analyses for π N scattering data. Therefore, experiments on photoproduction of mesons have been planned and executed, in order to find resonances with a comparatively large photocoupling, which have escaped observation before. The reaction γ N→ π N in particular allows for the extraction of 16 polarization observables.
An interesting mathematical problem associated with polarization measurements is the so called ’Complete Experiment’. Here, one investigates the content and size of a minimal subset of the 16 observables which still allows for an unambiguous determination of the underlying amplitudes. It can be shown that, at least in case numerically precise pseudo-data are investigated, 8 carefully selected observables can constitute a Complete Experiment. If a truncated partial wave analysis is done, fewer observables can be already sufficient.
The presentation will treat the Complete Experiment problem for truncated partial wave analyses and show preliminary results for an analysis of γ p→ π⁰ p, which utilizes 7 polarization observables measured in the second resonance region. Supported by the Deutsche Forschungsgemeinschaft (SFB/TR16).