Study of a 144 channel multi-anode hybrid avalanche photo-detector for the Belle II RICH counter

A new hybrid avalanche photo-detector has been developed as a photon sensor for the Belle II RICH counter. Single-photon response was investigated in the presence of a magnetic field and excellent performance was demonstrated. In addition, the radiation damage due to the neutron dose was studied. By building a prototype consisting of six photo-detectors, a test beam experiment was carried out. We successfully obtained a single-photon Cherenkov resolution of 13.5 mrad with 15.3 photoelectrons and achieved a π/Kπ/K separation of more than 6σ6σ at 4 GeV/c.