Four-neutrino model and the K2K experiment
  We investigate the neutrino oscillations of \nu_\mu beam at the K2K experiment in the four-neutrino model with three active and one sterile neutrinos, and compare them with the oscillations in the three-neutrino model. In the four-neutrino case, the effect of the \Delta m^2_{LSND} scale of mass-squared difference, derived from the LSND experiments, occurs in the survival probability P(\nu_\mu \to \nu_\mu) in the range of \Delta m^2 < 0.004 eV^2, where \Delta m^2 is the relevant one to the K2K experiment and corresponds to the atmospheric neutrino mass scale. Once the probability P(\nu_\mu \to \nu_\mu) is measured at the K2K, the allowed region of \Delta m^2 would turn out to be broader in the four-neutrino model than the one in the three-neutrino model. 
T. Hattori (Tokushima Univ.), T. Hasuike (Anan Col. Technology), S.   Wakaizumi (Tokushima Univ.)