https://doi.org/10.1140/epja/i2017-12194-8
Regular Article - Experimental Physics
Double-polarization observable G in neutral-pion photoproduction off the proton
1
Helmholtz-Institut für Strahlen, und Kernphysik der Universität Bonn, Bonn, Germany
2
Physikalisches Institut, Universität Bonn, Bonn, Germany
3
Petersburg Nuclear Physics Institute, Gatchina, Russia
4
Institut für Experimentalphysik I, Ruhr-Universität Bochum, Bochum, Germany
5
Institut für Physik, Universität Basel, Basel, Switzerland
6
Department of Physics, Florida State University, Tallahassee, FL, USA
7
II. Physikalisches Institut, Universität Gießen, Gießen, Germany
* e-mail: thiel@hiskp.uni-bonn.de
Received:
13
April
2016
Accepted:
14
December
2016
Published online:
18
January
2017
This paper reports on a measurement of the double-polarization observable G in photoproduction off the proton using the CBELSA/TAPS experiment at the ELSA accelerator in Bonn. The observable G is determined from reactions of linearly polarized photons with longitudinally polarized protons. The polarized photons are produced by bremsstrahlung off a diamond radiator of well-defined orientation. A frozen spin butanol target provides the polarized protons. The data cover the photon energy range from 617 to 1325 MeV and a wide angular range. The experimental results for G are compared to predictions by the Bonn-Gatchina (BnGa), Jülich-Bonn (JüBo), MAID and SAID partial wave analyses. Implications of the new data for the pion photoproduction multipoles are discussed.
© SIF, Springer-Verlag Berlin Heidelberg, 2017