  Background: The total inclusive cross sections obtained for quasielastic (QE)
scattering in the Mini Booster Neutrino Experiment (MiniBooNE) are
significantly larger than those calculated by all models based on the impulse
approximation and using the world average value for the axial mass of $M_A
\approx 1 \GeV$. This discrepancy has led to various, quite different
explanations in terms of increased axial masses, changes in the functional form
of the axial form factor, increased vector strength in nuclei, and initial
two-particle interactions. This is disconcerting since the neutrino energy
reconstruction depends on the reaction mechanism. Purpose: We investigate
whether exclusive observables, such as nucleon knock-out, can be used to
distinguish between the various proposed reaction mechanisms. We determine the
influence of 2p-2h excitations on the energy reconstruction. Method: We use the
Giessen Boltzmann--Uehling--Uhlenbeck (GiBUU) model to predict numbers and
spectra of knock-out nucleons. The model is extended by incorporating a simple,
but realistic treatment of initial 2p-2h excitations. Results: We show numbers
and spectra of knock-out nucleons and show their sensitivity to the presence of
2p-2h initial excitations. We also discuss the influence of 2p-2h excitations
on the neutrino energy reconstruction. Conclusions: 2p-2h excitations do lead
to an increase in the number $n$ of knock-out nucleons for $n \ge 2$ while only
the $n=1$ knock-out remains a clean signal of true QE scattering. The spectra
of knock-out nucleons do also change, but their qualitative shape remains as
before. In the energy reconstruction 2p-2h interactions lead to a downward
shift of the reconstructed energy; this effect of 2p-2h excitations disappears
at higher energies because the 2p-2h influence is spread out over a wider
energy range.
