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arxiv: 2511.03964 · v3 · submitted 2025-11-06 · ✦ hep-ex

The role of final-state interaction modeling in neutrino energy reconstruction and oscillation measurements

Yinrui Liu , Laura Munteanu , Stephen Dolan This is my paper

Pith reviewed 2026-05-18 00:32 UTC · model grok-4.3

classification ✦ hep-ex
keywords final-state interactionsneutrino energy reconstructionoscillation measurementsDUNEsystematic uncertaintieslong-baseline experimentsneutrino interactions
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The pith

Variations in final-state interaction modeling can distort reconstructed neutrino energies enough to mimic oscillation parameter shifts at DUNE.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper demonstrates that realistic differences in how final-state interactions are modeled in neutrino event simulations can change the reconstructed neutrino energy spectrum by amounts that match or exceed the effects expected from changes in oscillation parameters at the precision of next-generation experiments. Using the DUNE neutrino flux and baseline as an example, these distortions can imitate shifts in the mass splitting Δm²₃₂ or the CP-violating phase δ_CP. This creates a potential degeneracy that could affect the accuracy of oscillation measurements. The analysis concludes that improved theoretical models and dedicated new measurements are required to characterize final-state interactions and enable reliable near-detector constraints.

Core claim

Without additional theoretical and experimental efforts, realistic variations in final-state-interaction (FSI) modeling may alter reconstructed neutrino-energy spectra at next-generation long-baseline experiments by amounts comparable to, or larger than, variations induced by oscillation-parameter shifts at their projected precision. Using the DUNE flux and baseline as a case study, these FSI-driven distortions can mimic the effects of changes in the oscillation parameters Δm²₃₂ or δ_CP, producing a potential degeneracy.

What carries the argument

Final-state interaction (FSI) modeling in neutrino event generators, which governs outgoing particle kinematics and thereby maps true neutrino energy to the reconstructed energy from observed final-state particles.

Load-bearing premise

The specific FSI modeling variations explored are representative of the true theoretical uncertainty range and the simulation framework accurately propagates these variations into reconstructed energy spectra without unaccounted biases.

What would settle it

A high-statistics comparison of reconstructed neutrino energy spectra at a DUNE near detector against predictions from multiple FSI models that would show whether the distortions are smaller than, equal to, or larger than the spectral shifts from projected changes in Δm²₃₂ or δ_CP.

Figures

Figures reproduced from arXiv: 2511.03964 by Laura Munteanu, Stephen Dolan, Yinrui Liu.

Figure 1
Figure 1. Figure 1: The simulated distribution of neutrino energy [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Comparison of the simulated νµ reconstructed energy spectra and an oscillated DUNE experiment flux using different FSI models, to variations of ∆m2 32. This is simulated for neutrino (top) and antineutrino (bot￾tom) beam modes. In each sub-figure, reconstructed energy spectra under different FSI models are shown as histograms and ±0.4% ∆m2 32 variations are shown with shaded blue (+) and red (-) bands cent… view at source ↗
Figure 3
Figure 3. Figure 3: Comparison of the simulated νe reconstructed energy spectra and an oscillated DUNE experiment flux using different FSI models, to variations of ∆m2 32. This is simulated for neutrino (top) and antineutrino (bottom) beam modes. The left and right correspond to δCP = 0 and δCP − π/2, respectively. Other figure elements follow the same conventions as described in [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Comparison of the simulated νµ reconstructed energy spectra and an oscillated DUNE experiment flux using different FSI models, to ±1.3% variations of sin2 θ23. This is simulated for neutrino (top) and antineutrino (bottom) beam modes. Other figure elements follow the same conventions as described in [PITH_FULL_IMAGE:figures/full_fig_p008_4.png] view at source ↗
read the original abstract

We present a quantitative demonstration that, without additional theoretical and experimental efforts, realistic variations in final-state-interaction (FSI) modeling may alter reconstructed neutrino-energy spectra at next-generation long-baseline experiments by amounts comparable to, or larger than, variations induced by oscillation-parameter shifts at their projected precision. Using the DUNE flux and baseline as a case study, we show that these FSI-driven distortions can mimic the effects of changes in the oscillation parameters $\Delta m^2_{32}$ or $\delta_{\rm CP}$, producing a potential degeneracy. Our analysis thereby underscores the urgent need for an improved characterisation of FSI to enable robust constraints from near detectors through the development of theory-driven uncertainty parameterisations benchmarked with dedicated new measurements.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript claims that without additional theoretical and experimental efforts, realistic variations in final-state-interaction (FSI) modeling may alter reconstructed neutrino-energy spectra at next-generation long-baseline experiments by amounts comparable to, or larger than, variations induced by oscillation-parameter shifts at their projected precision. Using the DUNE flux and baseline as a case study, these FSI-driven distortions can mimic the effects of changes in the oscillation parameters Δm²₃₂ or δ_CP, producing a potential degeneracy. The analysis underscores the urgent need for an improved characterisation of FSI to enable robust constraints from near detectors through the development of theory-driven uncertainty parameterisations benchmarked with dedicated new measurements.

Significance. If the central result holds after addressing the concerns below, the work would be significant in identifying a potentially important systematic uncertainty for precision neutrino oscillation measurements at facilities such as DUNE. By providing a concrete demonstration of possible degeneracies between FSI modeling choices and key oscillation parameters, the paper would motivate targeted theoretical and experimental efforts to improve FSI constraints, which could directly impact the robustness of future long-baseline analyses.

major comments (2)
  1. [Simulation and Analysis Methods] The manuscript does not benchmark the selected FSI modeling variations (different tunes, parameter shifts, or model switches) against observed discrepancies in MINERvA or T2K final-state observables. This is load-bearing for the central claim because the reported size of the reconstructed-energy distortions, and thus their comparability to Δm²₃₂ or δ_CP shifts, depends on the variations lying inside the range allowed by current theory and experiment.
  2. [Results] The analysis does not propagate the FSI variations through a full near-detector constraint chain. Without this step, it remains unclear whether the demonstrated degeneracy with oscillation parameters would survive the standard near-detector constraints that are expected to be applied at DUNE.
minor comments (2)
  1. [Abstract] The abstract would benefit from including at least one quantitative estimate of the reported spectral distortion magnitude to give readers immediate context for the claimed effect size.
  2. [Figures] Figure captions and axis labels should explicitly state the specific FSI model variants shown in each panel to improve clarity for readers unfamiliar with the generator tunes.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful and constructive review. The comments highlight important aspects of validating the FSI variations and assessing the impact of near-detector constraints. We address each major comment below and indicate the revisions we will make to the manuscript.

read point-by-point responses

  1. Referee: [Simulation and Analysis Methods] The manuscript does not benchmark the selected FSI modeling variations (different tunes, parameter shifts, or model switches) against observed discrepancies in MINERvA or T2K final-state observables. This is load-bearing for the central claim because the reported size of the reconstructed-energy distortions, and thus their comparability to Δm²₃₂ or δ_CP shifts, depends on the variations lying inside the range allowed by current theory and experiment.

    Authors: We agree that direct benchmarking against MINERvA and T2K final-state observables is necessary to confirm that the chosen FSI variations remain within the range permitted by existing data. In the revised manuscript we will add a dedicated subsection to the methods that compares the selected tunes, parameter shifts, and model switches to published MINERvA and T2K measurements of proton and pion multiplicities, transverse momentum distributions, and nuclear de-excitation signatures. This addition will explicitly link the magnitude of the reported energy-spectrum distortions to the size of discrepancies already observed in current experiments. revision: yes

  2. Referee: [Results] The analysis does not propagate the FSI variations through a full near-detector constraint chain. Without this step, it remains unclear whether the demonstrated degeneracy with oscillation parameters would survive the standard near-detector constraints that are expected to be applied at DUNE.

    Authors: We recognize that a complete near-detector constraint analysis would be required to determine whether the FSI-induced degeneracy persists after standard ND fits. Implementing the full DUNE near-detector simulation and oscillation-parameter fitting chain lies beyond the scope of the present work, which focuses on isolating the potential size of the effect prior to constraints. In the revised manuscript we will expand the discussion to include a qualitative assessment, based on published ND constraint studies, of how much of the FSI variation might be absorbed by near-detector data and what residual uncertainty would remain for the far-detector spectrum. We will also outline the additional steps needed for a quantitative propagation in future analyses. revision: partial

Circularity Check

0 steps flagged

No circularity: direct simulation comparison of FSI variations to oscillation effects

full rationale

The paper conducts a simulation-based sensitivity study by applying varied FSI models from standard event generators to DUNE flux and baseline, then directly comparing the resulting shifts in reconstructed neutrino energy spectra against the size of shifts induced by changes in oscillation parameters such as Δm²₃₂ and δ_CP. No load-bearing step reduces by construction to a fitted parameter, self-citation chain, or ansatz imported from the authors' prior work; the central demonstration relies on explicit propagation through external simulation frameworks without fitting to the target oscillation observables or redefining quantities in terms of themselves. The analysis is therefore self-contained as a computational illustration of potential degeneracy.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on the domain assumption that current neutrino event generators provide a sufficient basis for exploring realistic FSI variations and that the DUNE flux and baseline are representative of next-generation long-baseline setups.

axioms (1)
  • domain assumption Standard neutrino interaction models in event generators capture the relevant final-state interaction physics for the purpose of this uncertainty study.
    Invoked when the paper varies FSI modeling within these frameworks to produce the reported spectral distortions.

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