Barrel photon detector of the KEK KL0→π0νν¯ experiment

Large lead/scintillator sandwich-type photon detectors, sensitive to visible energy depositions of 1 MeV, have been built for the KL0→π0νν¯ experiment at the KEK 12-GeV proton synchrotron. The front barrel (FB) is composed of 16 modules with a length of 2.75 m, forming the 1.5 m-diameter cylinder. The main barrel (MB) is composed of 32 modules with a length of 5.5 m, forming a 3.5 m-diameter cylinder. Scintillation light is read out through wavelength-shifter (WLS) fibers. In this paper, the design, construction and performance of these detectors together with some R&D results are reported.