The parity experiment at the Bonn Isochronous Cyclotron probed the weak interaction in a pure hadronic channel i.e. scattering. This kind of experiment was proposed in 1972 by Simonius [1] and has the advantage of a relatively simple theoretical interpretation at the expense of the accuracy (some 10^-8) the longitudinal analyzing power A_z has to be measured. As this kind of test constitutes a null-experiment the sensitivity is risen by 2-3 orders of magnitude. Moreover, since a polarization observable is measured no absolute cross-sections have to be determined. In order to suppress drifts of parameters all means of correlations in the time-domain  can be applied, improving the sensitivity by another 2-3 orders of magnitude.

The experiment at Bonn was planned in 1980 and carried out until June 1991 with the final result A_z = (-0.93�0.20�0.05)�10^-7[ 2,20]. After a first stage (1985) tests demonstrated the feasibility of the experiment, resulting in improvements of the source for polarized protons, the beam-line, experimental set-up and data acquisition. Finally, the ratio of time used for care of the source, accelerator and beam-handling to the time spent for data-taking could be improved from 80/20 to 10/90. Intermediate results can be found in [3,4]. In all, 16 diploma theses  [5-20] and 2 PhD theses [21,22] have contributed to the experiment.