High granularity scintillating fiber trackers based on Silicon Photomultiplier

Scintillating fibers coupled to photosensors provide flexible, fast and high granularity detectors which are able to work in high rate environment. We will report about the performances obtained with multi-layer detector prototype based on 250 mm multi-clad square scintillating fibers, 20 cm long, coupled to 1:31:3mm2 active area silicon photomultiplier (SiPMs). Current measurements show results never reached up to now: high detection efficiency for minimum ionizing particles (m.i.p.) already for a single layer (> 90%, mean collected light/fiber 8.5 phe). Also a good spatial resolution can be achieved by keeping the optical cross-talk between fibers at a negligible level (<1%), a level has been achieved by coating the fibers with aluminum.. Finally, the time resolution of the order of 500 ps has been achieved for m.i.p. in a single layer configuration. The resolution improves with increasing the number of detector layers. All measurements have been supported with a Monte Carlo simulation based on Geant4 and a custom code, describing the response of the SiPMs.