Study of a very long scintillating fiber TOF detector. Application to the Tau-Charm-Factory

We have studied the time resolution, light yield and attenuation length of a scintillation counter prototype made of a bundle of plastic scintillating fibers 2 mm in diameter 6.15 m long and 5 cm × 5.5 cm in cross section. In order to achieve 3σ K-π separation at 1 GeV/c via TOF in the Tau-Charm-Factory geometry one requires ≈ 120 ps time resolution. Measurements using one photomultiplier on cosmic muons crossing through the center of the counter give a resolution σ = (237±5) ps thus indicating that two layers of counters each looked at by photomultipliers at both ends can provide the needed time resolution.