Measurement of the vector analyzing power of the vector pp →{pp}sπ0 reaction at intermediate energies at ANKE/COSY

The reaction vector pp→{pp}sπ0, where {pp}s is a proton pair with an excitation energy E{pp}< 3 MeV, has been observed with the ANKE spectrometer at COSY-Juelich using a polarized beam with energies 353, 500, 550 and 700 MeV. The data have been processed to obtain the vector analyzing power Ay of the reaction. The setup acceptance covers most of the angular range at 353 MeV and forward angles at the higher beam energies, allowing one to obtain the Ay angular dependence. From the results of the analysis at 353 MeV, one can extract information on the pion d-wave contribution, which is important for Chiral Perturbation Theory tests at this energy. At higher energies the results are compared with a phenomenological model and this gives additional information about Δ-nucleon dynamics.