Measurement of Cherenkov photons with silicon photomultipliers

In addition to their other advantages, silicon photomultipliers (SiPMs) are insensitive to magnetic fields, so they would be attractive as photon detectors for ring imaging Cherenkov counters inside large magnetic spectrometers. In view of the foreseen upgrade of the particle identification system of the Belle spectrometer, we have investigated the possibilities offered by these new photon detectors. Cherenkov photons emitted by cosmic ray particles in an aerogel radiator have been detected with SiPMs for the first time. Estimates and tests show that light concentrators may improve the detection efficiency, thus showing promise for an SiPM based RICH detector.