  Neutrino oscillation probabilities, which are being measured in long-baseline
experiments, depend on neutrino energy. The energy in a neutrino beam, however,
is broadly smeared so that the neutrino energy in a particular event is not
directly known, but must be reconstructed from final state properties. In this
paper we investigate the contributions from different reaction mechanisms on
the energy-reconstruction method widely used in long-baseline neutrino
experiments. Difference between the true-QE and QE-like cross sections in
MiniBooNE experiment is investigated in details. It is shown, that fake QE-like
events lead to significant distortions in neutrino energy reconstruction.
Flux-folded and unfolded cross sections for QE-like scattering are calculated
as functions of both true and reconstructed energies. Flux-folded momentum
transfer distributions are calculated as functions of both true and
reconstructed momentum transfer. Distributions versus reconstructed values are
compared with the experimental data. Also presented are the conditional
probability densities of finding a true energy for a given reconstructed
energy. It is shown, how the energy reconstruction procedure influences the
measurement of oscillation parameters in T2K experiment. For the reconstruction
procedure based on quasielastic (QE) kinematics, all other reaction channels
beside true-QE scattering show a shift of the reconstructed energy towards
lower values as compared to the true energy. On average in the MiniBooNE and
T2K experiments the shift is 100 - 200 MeV and depends on energy. The
oscillation signals are similarly affected. These uncertainties may limit the
extraction of a CP violating phase from an oscillation result.
