New measurements on the nucleon structure with MAMI

The Institut fuer Kernphysik in Mainz is operating the microtron MAMI producing a high-quality continuous beam of electrons with an endpoint energy of 1.5-1.6 GeV for hadron and nuclear physics. The spectrometer facility has been used to measure the proton elastic form factors with unprecedented sub-percent precision, being sensitive for the first time to detailed structures in the form factor as currently under debate. Since 2008 the magnetic spectrometer Kaos is used in the facility for kaon spectroscopy addressing some important issues in the field of elementary kaon photoelectro-production. The Crystal Ball and TAPS set-up was equipped with a frozen-spin polarized target to perform new high-precision, high-statistics measurements of neutral meson production and polarization observables on the nucleon. At the A4 experimental set-up new measurements of the parity violating asymmetry in elastic electron scattering were performed, leading to an improved determination of the strange quark contributions to the vector form factors of the proton. To conclude, the electron accelerator MAMI represents a unique research tool for precision measurements with the electroweak probe that is now also covering the strangeness sector.