Measurement of Polarisation Observables using Linearly Polarised Photons with the Crystal Ball

In order to further study and expand the kinematic coverage of polarisation observ-ables in pseudoscalar meson photoproduction, a measurement of polarisation observ-ables has been performed at the MAMI facility in Mainz, Germany. The measure-ment used a beam of linearly polarised photons using the coherent bremsstrahlung method and the Glasgow Tagged Photon Spectrometer. The photon beam was in-cident on an lH2 target in order to produce the meson photoproduction reaction γp → pi0p. This target was housed in the centre of the Crystal Ball detector which was used to detect the reaction products. A carbon polarimeter was used to measure the polarisation of the recoiling proton through secondary scattering. The polar-isation observables for pseudoscalar meson photoproduction which were measured included: Σ, the modulation induced in the reaction products by the linearly po-larised photon beam; Ox, the transfer of linear polarisation from the beam to the recoiling proton; and T, the polarisation inherent in the target proton. These mea-surements were performed over a wide kinematic range in both photon energy and polar angle in the centre of mass system, and were compared to three partial wave analyses, SAID, MAID and Bonn-Gatchina. The results contribute to the ongo-ing search for a complete understanding of the nucleon’s excitation spectrum, and significantly enhance the world dataset for these polarisation observables