Study of RICH Counter with Silica Aerogel Radiator

A proximity focusing RICH using aerogel as the Cherenkov radiator is being developed as a new particle identification device for the Belle detector upgrade. A prototype counter was constructed with recently produced aerogel samples, arranged in a focusing configuration, and a test beam experiment was carried out in order to evaluate the performance of the apparatus. With this device we have achieved a pi-K separation that exceeded 5sigma at 4 GeV/c, with ap9 detected photoelectrons per track. We have also studied the influence of various parameters like radiator refractive index combinations on the performance of the apparatus.