Ring Imaging Cherenkov counters (RICH) are often used for charged particle identification in B physics experiments, an example being the Belle II spectrometer. In the Belle II RICH the number of detected photons per particle is of the order of 10 and a position sensitive single photon sensor is needed to successfully reconstruct the image of a ring. Furthermore, the sensor has to operate in a high magnetic field without degradation of efficiency. The Silicon Photomultiplier (SiPM) is a novel solid state sensor capable of registering single photons, which we tested as a photon counter in RICH. We constructed a prototype detector module that operated in a binary mode, reducing the complexity of front-end electronics. By employing a narrow time detection window we were able to reject most of the noise. The signal to noise ratio was further improved by employing light concentrators. Despite the main deficiency of SiPMs, namely a high dark count rate, with our prototype detector module we were able to detect a high number photons, approximately 32 per ring. This would result in approx. 8 sigma separation between kaons and pions in the kinematic region p = 1- 4 GeV/c.
Slides can be found here: https://indico.ph.qmul.ac.uk/indico/conferenceDisplay.py?confId=133