A method for detecting $\nu_\tau$ appearance in the spectra of   quasielastic CC events
  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. 
A.E. Asratyan, G.V. Davidenko, A.G. Dolgolenko, V.S. Kaftanov, M.A.   Kubantsev, V.S. Verebryusov