Test of the GENIE neutrino event generator against ${}^{16}$O $(e,e'p)$ data: Reduced cross section

TL;DR

The paper tests GENIE v3 CCQE models against precise semiexclusive electron-scattering data on $^{16}$O to probe bound-nucleon momentum distributions and nucleon final-state interactions. Using the reduced cross section $\sigma_{red}$ as a distorted spectral function within RDWIA/PWIA, the authors benchmark four GENIE ground-state models and two FSI schemes against Saclay and NIKHEF data. They find persistent discrepancies: GENIE overpredicts $\sigma_{red}$ at low missing momentum $p_m$ and often mis-shapes the $p_m$ dependence across kinematics, whereas RDWIA electron data align well with measurements, highlighting inadequacies in the nuclear ground-state and FSI treatments in GENIE. The work demonstrates that precise electron-scattering data provide a robust benchmark for nuclear models in neutrino event generators and motivates adopting more sophisticated spectral-function and RDWIA-like approaches to improve CCQE semiexclusive simulations.

Abstract

The reduced cross section of the semiexclusive $(l,l'p)$ lepton scat tering process irrespective of the type of interaction is determined mainly by bound nucleon momentum distribution in target and nucleon final state interaction with residual nucleus. These cross sections can be identified with distorted nuclear spectral functions and therefore are similar up to Coulomb c orrections for neutrino and electron scattering on nuclei. In this article we exploit this similarity and use data with precise kinematics and large statistics for semiexclusive electron scattering on oxygen target to test models employed in the GENIE neutrino event generator. We find that these models can not reproduce well the measured reduced cross sections in all allowed kinematic region and the GENIE event generator needs to better describe both the nuclear ground states and nucleon final state interaction. The approach presented in this paper provides a great opportunity to test better the accuracy of nuclear models of quasielastic neutrino-nucleus scattering, employed in neutrino event generators.

Figures (10)

• Figure 1: Initial nucleon momentum distribution for ${}^{16}$O according to the GENIE implementation of G18_02a (FG, solid line), G18_10a (LFG, dashed line), and effsf (dot-dashed) models.
• Figure 2: Probability density distribution vs missing energy $E_{mis}$ calculated for neutrino energy $\hbox{\boldmath $\varepsilon$}_{\nu}=0.5$ GeV. Left panel: PDF for (1p+Nn) events calculated with the G18_02 (solid line), G18_10 (dashed line) and G21_11 (dot-dashed line) models and for (1p+0n) events calculated within G21_11 (dotted line) model. Right panel: PDF for (1p+0n) set calculated with effsh (dotted line) model and PDF for (1p+Nn) set calculated within the effsf (dot-dashed line) models.
• Figure 3: Comparison of the RDWIA electron, neutrino, and antineutrino reduced cross sections BAV1 for the removal of nucleons from $1p_{1/2}$ and $1p_{3/2}$ shells of oxygen for Saclay Saclay perpendicular kinematics. Saclay data for beam energy $E_{beam}=500$ MeV, proton kinetic energy $T_p=100$ MeV and $Q^2=0.3$GeV${}^2$.
• Figure 4: The RDWIA electron reduced cross section BAV1 for the removal of protons from $1s$, $1p$, and $1s+1p$ shells of ${}^{16}$O for Saclay kinematics (upper panel) and ratio $R_{1p}$ (lower panel) as functions of missing momentum. Also shown (upper panel) are Saclay data for the removal protons from $1p=1p_{1/2}+1p_{3/2}$ shell.
• Figure 5: The RDWIA calculation of electron, neutrino, and antineutrino reduced cross sections BAV1 for the removal of nucleons from $1p_{1/2}$ and $1p_{3/2}$ shells of ${}^{16}$O for NIKHEF parallel kinematics NIK1NIK2 as function of $p_m$. NIKHER data for beam energy $E_{beam}=304-521$ MeV, proton kinetic energy $T_p=89-99$ MeV and $Q^2$ is varied.