Threshold π0π0 photoproduction on transverse polarised protons at MAMI

Polarisation-dependent differential cross sections σTσT associated with the target asymmetry T   have been measured for the reaction γp→→pπ0 with transverse target polarisation from π0π0 threshold to photon energies of 190 MeV. The data were obtained using a frozen-spin butanol target with the Crystal Ball / TAPS detector set-up and the Glasgow photon tagging system at the Mainz Microtron MAMI. Results for σTσT have been used in combination with our previous measurements of the unpolarised cross section σ0σ0 and the beam asymmetry Σ for a model-independent determination of S- and P  -wave multipoles in the π0π0 threshold region, which includes for the first time a direct determination of the imaginary part of the E0+E0+ multipole.