5 J un 2 00 6 Scintillator counters with multi - pixel avalanche photodiode readout for the ND 280 detector of the T 2 K experiment

The Tokai–to–Kamioka (T2K) experiment is a second generation long baseline neutrino oscillation experiment which aims at a sensitive search for the νe appearance. The main design features of the T2K near neutrino detectors located at 280 m from the target are presented. Scintillator counters developed for the T2K near detectors are described. Readout of the counters is provided via WLS fibers embedded into S–shape grooves in a scintillator and viewed from both ends by multi–pixel avalanche photodiodes operating in a limited Geiger mode. A description, operational principles and the results of tests of photosensors with a sensitive area of 1.1 mm2 are presented. A time resolution of 1.5 ns, a spatial resolution of 9.9–12.4 cm, and a MIP detection efficiency of more than 99% were obtained for scintillator detectors in a beam test. ∗Corresponding author. Email address: [email protected]