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arxiv: 2605.26877 · v1 · pith:DW363AIPnew · submitted 2026-05-26 · ⚛️ nucl-th · hep-ph

Azimuthal asymmetry in exclusive quasi-elastic neutrino-nucleus interactions

Marco Vanderpoorten , Ashish Kumar Jha , Mathias El Baz , Kajetan Niewczas , Federico Sanchez , Natalie Jachowicz This is my paper

Pith reviewed 2026-07-01 16:07 UTC · model grok-4.3

classification ⚛️ nucl-th hep-ph
keywords azimuthal asymmetryquasi-elastic scatteringneutrino-nucleus interactionsparity violationnuclear modelingenergy reconstructionweak interaction
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The pith

The outgoing nucleon in quasi-elastic neutrino-nucleus scattering shows an azimuthal asymmetry outside the lepton plane caused by parity violation.

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

The paper derives the general azimuthal distribution for the outgoing nucleon in exclusive quasi-elastic neutrino-nucleus scattering and identifies an overlooked dependence that produces an asymmetric distribution. This asymmetry arises specifically from parity violation in the weak interaction and varies with nuclear modeling choices and the shell structure of the initial nucleus. The resulting observable supplies additional information that can improve neutrino energy reconstruction in oscillation experiments. Calculations show the asymmetry persists after realistic momentum thresholds and intranuclear cascades are applied, remaining detectable with O(10^4) events on carbon-12 at 99 percent .

Core claim

The azimuthal angle distribution of the outgoing nucleon in exclusive quasi-elastic neutrino-nucleus interactions is asymmetric, with a preference for emission outside the lepton scattering plane. This asymmetry is produced by parity violation in the weak interaction. In cross-section calculations the size of the asymmetry depends on the nuclear model employed and on the shell structure of the target nucleus, supplying a new observable for neutrino energy reconstruction.

What carries the argument

The azimuthal angle distribution of the outgoing nucleon, obtained from the general form of the quasi-elastic cross section and containing parity-violating contributions from the weak interaction.

If this is right

  • The asymmetry supplies a new observable that depends on nuclear modeling and shell structure.
  • It can be used as additional input for neutrino energy reconstruction in oscillation experiments.
  • The effect remains measurable after momentum detection thresholds and intranuclear cascades are applied.
  • O(10^4) events on carbon-12 suffice to reach 99 percent on the asymmetry.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The asymmetry could serve as an independent test of nuclear models used in neutrino event generators.
  • Similar azimuthal effects may appear in other parity-violating weak processes on nuclei.
  • Detector designs that resolve azimuthal angles could extract extra nuclear-structure information from existing data sets.
  • The size of the asymmetry might vary with neutrino energy in ways that help separate interaction channels.

Load-bearing premise

The predicted asymmetry stays large enough to be seen at 99 percent with O(10^4) events after realistic momentum cuts and an intranuclear cascade are included.

What would settle it

No statistically significant azimuthal asymmetry appears in a sample of roughly 10,000 quasi-elastic events on carbon-12 after the stated detection thresholds and cascade modeling.

Figures

Figures reproduced from arXiv: 2605.26877 by Ashish Kumar Jha, Federico Sanchez, Kajetan Niewczas, Marco Vanderpoorten, Mathias El Baz, Natalie Jachowicz.

Figure 1
Figure 1. Figure 1: FIG. 1: Overview of the kinematics of quasi-elastic [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3: The central phase shift as a function of [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4: Azimuthal angle distributions of the hadronic response functions for quasi-elastic [PITH_FULL_IMAGE:figures/full_fig_p007_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5: Azimuthal angle distributions of the differential cross section for quasi-elastic [PITH_FULL_IMAGE:figures/full_fig_p007_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6: Azimuthal angle distributions of the differential cross section for quasi-elastic [PITH_FULL_IMAGE:figures/full_fig_p007_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7: Azimuthal angle distributions of the differential cross section for charged-current quasi-elastic scattering. [PITH_FULL_IMAGE:figures/full_fig_p009_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: FIG. 8: Normalized differential cross sections for nucleons from different shells for [PITH_FULL_IMAGE:figures/full_fig_p009_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: FIG. 9: Top: Distribution of the reconstructed [PITH_FULL_IMAGE:figures/full_fig_p010_9.png] view at source ↗
read the original abstract

In neutrino oscillation experiments, exclusive measurements of neutrino-nucleus interactions play a critical role, by providing the theoretical and experimental input needed for a reliable estimation of the neutrino energy. In this paper, we derive the general form of the azimuthal angle distribution for quasi-elastic scattering, focusing on a dependency that has been routinely overlooked. We demonstrate that the outgoing nucleon exhibits a preference for emission outside the lepton scattering plane, with an asymmetric azimuthal distribution. In the context of neutrino-nucleus scattering, we argue that this asymmetry is caused by parity violation in the weak interaction. Furthermore, we show that in cross section calculations the asymmetry is sensitive to nuclear modeling choices and to the shell structure of the initial nucleus, thus providing a novel source of information for energy reconstruction in neutrino experiments. We study the experimental feasibility of observing this effect by applying a realistic momentum detection threshold and an intranuclear cascade. We estimate that the asymmetry is observable with $\mathcal{O}$($10^4$) events at the 99% confidence level for neutrino interactions on $^{12}$C, suggesting that the effect is within reach of the current generation of neutrino detectors.

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 paper derives the general form of the azimuthal angle distribution in exclusive quasi-elastic neutrino-nucleus scattering and shows that the outgoing nucleon has a preference for emission outside the lepton scattering plane, producing an asymmetric azimuthal distribution. It attributes this asymmetry to parity violation in the weak interaction and demonstrates its sensitivity to nuclear modeling choices and the shell structure of the target nucleus. The work further studies experimental observability by applying a realistic nucleon momentum threshold and an intranuclear cascade model, concluding that the effect remains detectable at the 99% confidence level with O(10^4) events on 12C and could serve as a new input for neutrino energy reconstruction.

Significance. If the central derivation of the azimuthal asymmetry is correct and the effect survives realistic final-state interactions at the claimed magnitude, the result would supply a previously overlooked observable that is directly sensitive to both the weak interaction structure and nuclear dynamics. This could furnish an independent handle on energy reconstruction systematics in neutrino oscillation experiments, complementing existing inclusive and exclusive channels.

major comments (2)
  1. [experimental feasibility discussion (abstract and results)] The feasibility claim in the abstract and the corresponding results section states that the asymmetry remains observable after the intranuclear cascade and momentum threshold, yet provides no explicit numerical value for the post-cascade asymmetry parameter A or the dilution factor. Without these quantities or the associated statistical power calculation, it is not possible to verify whether the 99% CL reach with O(10^4) events on 12C still holds once the cascade randomizes the azimuthal angle.
  2. [nuclear modeling and shell-structure results] The sensitivity of the asymmetry to shell structure is asserted, but the manuscript does not show that this sensitivity survives the same intranuclear cascade modeling used for the observability estimate; if the cascade washes out shell-specific features, the claimed novel source of information for energy reconstruction would be compromised.
minor comments (2)
  1. [formalism section] Notation for the azimuthal angle and the lepton scattering plane should be defined once at first use and used consistently thereafter.
  2. [results] The manuscript would benefit from a table summarizing the asymmetry values before and after the cascade for the different nuclear models considered.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading of our manuscript and the constructive comments. We respond to each major comment below.

read point-by-point responses

  1. Referee: [experimental feasibility discussion (abstract and results)] The feasibility claim in the abstract and the corresponding results section states that the asymmetry remains observable after the intranuclear cascade and momentum threshold, yet provides no explicit numerical value for the post-cascade asymmetry parameter A or the dilution factor. Without these quantities or the associated statistical power calculation, it is not possible to verify whether the 99% CL reach with O(10^4) events on 12C still holds once the cascade randomizes the azimuthal angle.

    Authors: We agree that the manuscript does not report explicit numerical values for the post-cascade asymmetry parameter A or the associated dilution factor, even though the observability estimate incorporates the intranuclear cascade and momentum threshold. To permit independent verification of the 99% CL claim with O(10^4) events, we will add these quantities together with the statistical power calculation in the revised manuscript. revision: yes

  2. Referee: [nuclear modeling and shell-structure results] The sensitivity of the asymmetry to shell structure is asserted, but the manuscript does not show that this sensitivity survives the same intranuclear cascade modeling used for the observability estimate; if the cascade washes out shell-specific features, the claimed novel source of information for energy reconstruction would be compromised.

    Authors: The sensitivity to shell structure is shown within the impulse-approximation framework. The manuscript does not demonstrate that this sensitivity persists after the intranuclear cascade applied in the feasibility study. We will either extend the calculations to verify survival of the shell-specific features under the cascade or qualify the claim regarding its utility for energy reconstruction in the revised version. revision: yes

Circularity Check

0 steps flagged

No circularity detected; derivation follows from weak interaction formalism and applied nuclear models

full rationale

The paper derives the azimuthal distribution from the standard contraction of lepton and hadron tensors, identifying the parity-violating imaginary interference terms as the source of the asymmetry. It then computes the effect's dependence on nuclear models and shell structure via cross-section evaluations, followed by a simulation-based estimate of observability after momentum cuts and intranuclear cascade. No quoted steps equate a claimed prediction to a fitted input by construction, invoke self-citations as load-bearing uniqueness theorems, or rename known results; the chain remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review. No explicit free parameters, axioms, or invented entities are stated. The claim that the asymmetry is caused by parity violation relies on standard weak interaction properties, but nuclear modeling details are unspecified.

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