The experimental data and the theoretical predictions for reactions with three nucleons at low and intermediate energies are today at variance. We plan to make an extensive study of a large set of spin observables in the three nucleon continuum in proton deuteron breakup reactions between 30 and 50 MeV proton beam energies, an energy range where previous measurements are rather limited and where the predictive power of chiral perturbation theory is reliable. The longstanding physics question of the existence and nature of possible three-nucleon forces, will be studied with large coverage provided by an optimized silicon detector barrel, and flexibility utilizing the sampling method, a technique developed specifically for the complex analysis of three particle final states, providing a direct comparison between experiment and theory. The experiment will be done at COSY at a newly installed low beta section of the accelerator ring using a stored polarized beam and a polarized internal gas target.
The consistent inclusion of three-nucleon forces within chiral perturbation theory will offer a solid theoretical interpretation of the measurements.