Beam test of FARICH prototype with digital photon counter

Abstract In June 2012 we tested a Focusing Aerogel RICH detector prototype based on Digital Photon Counters (DPC) by Philips at the CERN PS T10 beam line with a particle momentum up to 6 GeV/ c . The prototype comprises a 20×20 cm 2 photon detector with 48×48 DPC pixels. In order to reduce the dark count rate, the photon detector was cooled to −40 °C in addition to disabling individual DPC's microcells. A four layer focusing aerogel radiator with 200 mm focal distance was studied. We obtained a Cherenkov angle resolution of 3.61±0.04 mrad. The mean number of photoelectrons in a ring is 12. Directly measured π / K separation at 6 GeV/ c momentum is 3.5 σ , μ / π separation is 5.3 σ at 1 GeV/ c . A comparison with a Monte Carlo simulation is presented as well.