Study of 144-channel hybrid avalanche photo-detector for Belle II RICH counter

For the upgrade of the Belle detector at the KEKB collider, we are developing a proximity focusing ring imaging Cherenkov detector using a silica aerogel as a radiator. An array of 144 channel HAPD (Hybrid Avalanche Photo Detector) will be used as the photo-detector. We have measured performance of the HAPDs, and succeeded to read out single-photon signals from the HAPD using custom-made ASICs that have been developed for this purpose. We have also performed a beam test with a 2 GeV/c electron beam and demonstrated more than 4σK/π separation performance at 4 GeV/c.