Physics potential of future long baseline neutrino oscillation experiments with KEK-JAERI HIPA

We study physics potential of Very Long Base-Line (VLBL) Neutrino-Oscillation Experiments with the High Intensity Proton Accelerator, which will be completed by the year 2007 in Tokai-village, Japan. As a target, a 100 kton-level water-$\check{\mathrm{C}}$erenkov detector is considered at 2,100 km away. Assuming the pulsed narrow-band ${\nu }_{\mu }$ beams, we study sensitivity of such experiments to the neutrino mass hierarchy, the mass-squared differences, one CP phase and three angles of the lepton-flavor-mixing matrix. We find that experiments at a distance 2,100 km can determine the neutrino mass hierarchy if the mixing matrix element $\mathrm{\mid }{U}_{e3}\mathrm{\mid }$ is not too small. The CP phase and $\mathrm{\mid }{U}_{e3}\mathrm{\mid }$ can be constrained if the large-mixing-angle solution of the solar-neutrino deficit is realized.