Assessing the accuracy of the GENIE event generator with electron-scattering data

TL;DR

This paper benchmarks the GENIE neutrino event generator against electron-scattering data to identify discrepancies in modeling complex nuclear physics relevant to future neutrino experiments like DUNE.

Contribution

It introduces a validation procedure using electron-scattering data to evaluate and improve GENIE's accuracy in the 1-4 GeV energy range.

Findings

Large discrepancies in pion production regimes.

Discrepancies observed across different nuclei, including hydrogen and deuterium.

Indications of mismodeled hadronic physics in GENIE.

Abstract

Precision neutrino oscillation experiments of the future---of which DUNE is a prime example---require reliable event generator tools. The 1--4 GeV energy regime, in which DUNE will operate, is marked by the transition from the low-energy nuclear physics domain to that of perturbative QCD, resulting in rich and highly complex physics. Given this complexity, it is important to establish a validation procedure capable of disentangling the physical processes and testing each of them individually. Here, we demonstrate the utility of this approach by benchmarking the GENIE generator, currently used by all Fermilab-based experiments, against a broad set of inclusive electron-scattering data. This comparison takes advantage of the fact that, while electron-nucleus and neutrino-nucleus processes share a lot of common physics, electron scattering gives one access to precisely known beam energies and scattering kinematics. Exploring the kinematic parameter range relevant to DUNE in this manner, we observe patterns of large discrepancies between the generator and data. These discrepancies are most prominent in the pion-producing regimes and are present not only in medium-sized nuclei, including argon, but also in deuterium and hydrogen targets, indicating mismodeled hadronic physics. Several directions for possible improvement are discussed.