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We describe the construction and performance of a scintillating fiber detector used in the near detector for the K2K (KEK to Kamioka, KEK E362) long baseline neutrino oscillation experiment. The detector uses 3.7 m long and 0.692 mm diameter scintillating fiber coupled to image-intensifier tubes (IIT), and a CCD camera readout system. Fiber sheet production and detector construction began in 1997, and the detector was commissioned in March, 1999. Results from the first K2K runs confirm good initial performance : position resolution is estimated to be about 0.8 mm, and track finding efficiency is 98 ± 2 % for long tracks (i.e., those which intersect more than 5 fiber planes). The hit efficiency was estimated to be 92 ± 2 % using cosmic-ray muons, after noise reduction at the offline stage. The possibility of using the detector for particle identification is also discussed.

A new tracking detector, scintillating track image camera (SCITIC) was used for hyperon-scattering experiments. Since the hyperon lifetimes are short, the low-energy hyperon-nucleon scattering can be studied only with a track detector used as an active target. The present experiment has shown that the SCITIC is a promising detector for the hyperon scattering experiments. Polarized hyperons AE þ were produced through pð þ ; K þ ÞAE þ reactions with a 1.6 GeV/c pion beam on a liquid scintillator of the active target. Three sets of SCITIC were used to record the pictures of AE þ production and scattering. A kaon spectrometer was used to trigger the SCITIC with a signal of kaon from the reaction. Left/right asymmetries of the AE þ p scattering were determined through analyses of the pictorial data, and the results were in accordance with a quark-model prediction that the asymmetry was large in the AE þ p scattering while it was small in the ÃN case.