Apparatus for spin-rotation measurements in pion-proton scattering at high energies

Abstract Measurements of spin-rotation parameters allow a complete determination of the pion-nucleon scattering amplitudes when the differential cross-section and the polarization normal to the scattering plane are known. This requires to scatter pions off a proton target that is polarized along a direction in the scattering plane, and to analyze the polarization of the recoil protons in a carbon plate polarimeter. Scintillation counter hodoscopes associated with fast logic allow the spark chambers of the polarimeter to be triggered mainly on elastic scatterings off the free protons in the target.