Results from the forward G0 experiment. Strange quark contribution to the nucleon structure

The G0 experiment is dedicated to the determination of the strange quark contribution to the electric and magnetic nucleon form factors for a large range of momentum transfers between 0.1 to 1 (GeV/c)2. This information is provided by the asymmetries of cross-sections measured with longitudinally polarized electrons in elastic electron-proton scattering and quasi-elastic electron-deuteron scattering. A set of measurements at two different Q2 will allow the complete separation of the electric and magnetic weak, as well as axial nucleon form factors. This report summarizes the physics case, gives details about the dedicated set-up used, and shows the results of the combination of the strange quark contribution in the electric and magnetic form factors of the protons. The experiment was performed at the Jefferson Laboratory, during years 2003 and 2004, and will be completed after backward-angle measurements in 2006, 2007. (orig.)