Neutrino energy reconstruction problems and neutrino oscillations

We discuss the accuracy of the usual procedure for neutrino energy reconstruction which is based on the quasielastic kinematics. Our results are described in terms of a probability distribution for a real neutrino energy starting from the reconstructed energy. Several factors are responsible for the deviations from the reconstructed value. The main one is the multinucleon component of the neutrino-nucleus interaction which in the case of Cherenkov detectors enters as a quasielastic cross section. Our procedure is discussed in connection to the MiniBooNE and T2K excess electron events from the conversion of muonneutrinos. The result is a reshaping effect which may influence the interpretation in terms of oscillation.