K2K far detector analysis

The far detector analysis for v(mu) disappearance in the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment is presented. The data used for this analysis is 8.9 x 10(19) protons on target (POT). A total of 107 events are observed in the far detector, Super-Kamiokande (SK), while 151(-10)(+12) are expected without v, oscillation. Spectral distortion of the reconstructed neutrino energy (E-v) is also observed, and it is consistent with v(mu) - v(tau) oscillation. The two-flavor v(mu) - v(tau) oscillation analysis is evaluated. We obtain an allowed region which is consistent with SK atmospheric neutrino oscillation analysis results. The probability to observe our results from a statistical fluctuation is 0.005% (4.0 sigma) in the case of no oscillation.