KEK to Kamioka Long Baseline Neutrino Oscillation Experiment K2K and Future Plan (<Special Issue>Physics of Neutrino - Commemorating Masatoshi Koshiba's Winning of the Nobel Prize in Physics -)

Abstract

The K2K collaboration has established the principles of the accelerator based long baseline neutrino experiment. The data prove the existence of neutrino oscillation with better than 99% confidence level and the indication of the neutrino spectrum distortion is observed. The results of oscillation analysis show that the oscillation parameters are consistent with the atmospheric neutrino results from Super-Kamiokande experiment.