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Implementation of a relativistic distorted wave impulse approximation model into the NEUT event generator

J. McKean1,*, R. González-Jiménez2,†, M. Kabirnezhad1,‡, J. M. Udías3,§, and Y. Uchida1,∥

  • 1Imperial College London, Department of Physics, London SW7 2BZ, United Kingdom
  • 2Departamento de Física Atómica, Molecular y Nuclear, Universidad de Sevilla, 41080 Sevilla, Spain
  • 3Grupo de Física Nuclear, Departamento de Estructura de la Materia, Física Térmica y Electrónica, Facultad de Ciencias Físicas, Universidad Complutense de Madrid and IPARCOS, CEI Moncloa, Madrid 28040, Spain

  • *Contact author: j.mckean21@imperial.ac.uk
  • †Contact author: raugj@us.es
  • ‡Contact author: m.kabirnezhad@imperial.ac.uk
  • §Contact author: jmudiasm@ucm.es
  • ∥Contact author: yoshi.uchida@imperial.ac.uk
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Phys. Rev. D 112, 032009 – Published 26 August, 2025

DOI: https://doi.org/10.1103/f7x5-snmz

Abstract

We describe the implementation of a model for charged-current quasielastic (CCQE) neutrino-nucleus scattering in the NEUT Monte Carlo event generator. This model employs relativistic momentum distributions obtained from mean-field theory and relativistic distorted waves to describe the initial and final nucleon states. Final state interactions, both elastic and inelastic, are modeled by combining distorted waves with NEUT’s intranuclear cascade, offering a more accurate representation of the interactions experienced by scattered nucleons. The model and its implementation in NEUT are described in detail and benchmarked against νμ−C12 scattering cross section measurements from T2K and MINERνA, as well as νμ−Ar40 measurements from MicroBooNE. The results, including transverse kinematic imbalance variables and scattered nucleon kinematics, show improved χ2 values compared to other CCQE models in NEUT. Furthermore, the model consistently predicts lower cross sections in CCQE-dominated regions, indicating the potential for further refinement, such as incorporating two-body currents or the use of more advanced nucleon axial form factors consistent with lattice QCD calculations.

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Phys. Rev. D 112, 032009– Published 26 August, 2025
  • Received 21 February 2025
  • Accepted 24 July 2025
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