The K2K SciBar Detector

SciBar is a fully-active scintillator tracking detector, which was newly installed at the near detector site of K2K long baseline neutrino oscillation experiment. The purposes of SciBar are to improve the measurement of the neutrino flux and to study neutrino interactions. Its construction was completed in August 2003. The neutrino data have been taken stably since October 2003. We describe its design, operation and basic performance. Preliminary results from an analysis of charged current events are also presented.