The Aerogel Ring Image Cherenkov Counter for Particle Identification in the Belle II Experiment

The Aerogel Ring Imaging Cherenkov (ARICH) counter is an upgrade of the forward endcap particle identification device in the upcoming Belle II experiment to secure \(4\sigma \) separation of charged kaons and pions up to momenta of 3.5 GeV. Developments and productions of Silica aerogel radiator, Hybrid Avalanche Photo Detector (HAPD) and its readout electronics, key components of the ARICH counter, are done while surrounding subsystems; a power supply, a readout slow control and a LED light injection system are in operation. And then construction of the ARICH counter is ongoing in parallel to cosmic ray test. Details of the detector components with construction status are described and the test operation are discussed in the letter.