Implementation and investigation of electron-nucleus scattering in the \textsc{NEUT} neutrino event generator

Abstract: Understanding nuclear effects is essential for improving the sensitivity of neutrino oscillation measurements. Validating nuclear models solely through neutrino scattering data is challenging due to limited statistics and the broad energy spectrum of neutrinos. In contrast, electron scattering experiments provide abundant high-precision data with various monochromatic energies and angles. Since both neutrinos and electrons interact via electroweak interactions, the same nuclear models can be applied to simulate both interactions. Thus, high-precision electron scattering data is essential for validating the nuclear models used in neutrino experiments. To enable this, the author has introduced a new electron scattering framework in the \textsc{NEUT} neutrino event generator, covering two interaction modes: quasielastic (QE) and single pion production. \textsc{NEUT} predictions of QE agree well with numerical calculations, supporting the validity of this implementation. From comparisons with \textsc{NEUT} predictions and inclusive electron scattering data, the momentum-dependent removal energy correction is derived, addressing effects beyond the plane wave impulse approximation. This correction is applied to neutrino interactions, observing significant changes in charged lepton kinematics. Notably, the reconstructed neutrino energy distribution shows a peak shift of approximately 20--30\,MeV, which is crucial for accurately measuring neutrino oscillation parameters.