Bochum 2009 – scientific programme

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HK: Fachverband Hadronen und Kerne

HK 69: Hadron Structure and Spectroscopy I

HK 69.6: Talk

Thursday, March 19, 2009, 18:15–18:30, H-ZO 20

Measurement of the double polarization asymmetry G in π⁰ and η photoproduction — •Annika Thiel — Helmholtz-Institut für Strahlen- und Kernphysik, Nußallee 14-16, D-53115 Bonn

The excitation spectrum of the proton consists of several overlapping resonances, which are difficult to disentangle. To determine the exact contributions and identify the resonances, a solution of the partial wave analysis has to be found. For a complete experiment, which leads to an unambiguous solution, at least 8 well chosen single and double polarization observables are needed. With the new Crystal-Barrel/TAPS experiment at ELSA, the measurement of double polarization parameters like E and G in different reactions is possible by using a circularly or linearly polarized photon beam on a longitunally polarized butanol target. The Crystal-Barrel/TAPS setup provides a nearly 4π angular coverage and a high detection efficiency for neutral states, which gives an ideal condition for the study of final state comprising neutral mesons. In this talk the first results of the G asymmetry measurement in the reactions γ^→p^→→pπ⁰ and γ^→p^→→pη, which utilizes linearly polarized photons in combination with the longitudinally polarized target, will be presented.
Supported by the Deutsche Forschungsgemeinschaft (SFB/TR 16).