  The concept of a very long baseline neutrino experiment with quasi
monochromatic neutrino beam and very large area underground detector is
discussed. The detector could be placed in the existing 20 km tunnel at IHEP,
Protvino. The High Intensity Proton Accelerators (HIPA) which are planned to be
built in Japan (JAERI-KEK, baseline of 7000 km) and Germany (GSI, baseline of
2000 km) as well as the Main Injector at Fermilab (7600 km) are considered as
possible sources of neutrino beams. The oscillations are analysed in the
three-neutrino scheme taking into account terrestrial matter effects. In the
proposed experiment it is feasible to observe the oscillation pattern as an
unique proof of the existence of neutrino oscillations. Precise measurements of
disappearance oscillation parameters of the muon neutrinos and antineutrinos
can be done within a reasonable time.
