Active target system with MPPC readout for hyperon-proton scattering experiment

We are developing an active target system with Multi-Pixeled Photon Counter (MPPC) readout for a hyperon-proton (YN) scattering experiment. The active target consists of scintillation fibers and each scintillation fiber is read by one MPPC. In order to check the detector response to a minimum ionization particle (MIP) and to a low energy proton, three test experiments with different beam conditions were performed. The light yield for the 450 MeV positron beam was obtaind to be about 7 photons (fired pixel), and the trajectory of the positron was clearly identified. The response to a low-energy protonwas checked using the proton beam of energies from 10 MeV to 50 MeV. The light yields were about 110 and 270 photons for protons penetrating through the fiber layers and stopped, respectively. The range of the proton in the active target corresponds to the energy of the proton. Finally, as the feasibility test of the YN scattering experiments, we have performed a proton scattering experiment using our imaging system. This system worked well under a rather high counting rate of about 50 kHz. The images of the proton-proton and proton-¹²C scattering events were clearly identified.