Cross-sections and spin observables in proton-proton elastic scattering: Results from EDDA at COSY

. At the Cooler-Synchrotron COSY/Jülich polarized and unpolarized elastic proton-proton scattering has been investigated with the EDDA-Experiment in the energy range ( T_p ≈ 0.5 -2.5 GeV). By taking scattering data during the acceleration of the beam with a large-acceptance ( θ_ c.m.≈ 30^∘ - 90^∘ ) detector, precise excitation functions for differential cross-section and analyzing power have been measured in small energy steps with consistent normalization with respect to luminosity and polarization. These data have helped to improve the determination of phase-shifts at higher energies and impose tight quantitative upper bounds on possible resonant contributions to pp elastic scattering, as they might arise from exotic 6-quark configurations. Recently, with polarized beam and target, the spin-correlation parameters A_ NN , A_ SS , and A_ SL have been determined at 10 energies between 0.8 and 2.5 GeV. The observable A_ SS has been measured the first time above 800 MeV and our results are in sharp contrast to phase-shift predictions at higher energies.