Strangeness physics at MAMI: First results and perspectives

During the last two years several experimental approaches to strange systems have been realized at the spectrometer facility of the Mainz Microtron MAMI. An instrument of central importance for the strangeness electro-production program is the magnetic spectrometer Kaos that was installed during 2003-8 and is now operated by the A1 collaboration in (e,e'K) reactions on the proton or light nuclei. Since 2008 kaon production at low four-momentum transfers off a liquid hydrogen target was studied. The measurements were sensitive to details of the phenomenological models describing the reaction. Two very prominent isobar models, Kaon-Maid and Saclay-Lyon A, differ in the number of contributing nucleon resonances and their longitudinal couplings at the kinematics measured at MAMI. In order to use Kaos as a zero-degree double-arm spectrometer a magnetic chicane comprising two compensating sector magnets was constructed and a new electron-arm focal-plane detector system was built.