  A method for detecting the transition \omutau in long-baseline accelerator
experiments, that consists in comparing the far-to-near ratios of the spectra
of quasielastic CC events generated by high- and low-energy beams of muon
neutrinos, is proposed. The test may be accessible to big water Cherenkov
detectors and iron--scintillator calorimeters, and is limited by statistics
rather than systematics.
