Experimental technique for antiproton-nucleus annihilation cross section measurements at low energy

The interaction of very low energy antiprotons (p¯s) and antineutrons (¯ ns) with nuclei is interesting for its influence on both fundamental cosmology and nuclear physics. Measuring the annihilation cross section of antimatter on matter can help in solving the universe matter-antimatter puzzle and could give relevant hints in the definition of strong interaction model parameters as well. The ASACUSA collaboration recently measured the antiproton-carbon annihilation cross section at 5.3 MeV of kinetic energy of the incoming antiproton. The experimental apparatus consisted in a vacuum chamber containing thin foils (∼0.7-1 µm) of carbon crossed by a bunched beam of antiprotons from the CERN Antiproton Decelerator (AD). The fraction of antiprotons annihilating on the target nucleons gives origin to charged pions which can be detected and counted by segmented scintillators placed outside the chamber. This work describes the experimental details of the apparatus and the technique to perform the cross section measurements.