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arxiv: 2509.16725 · v5 · submitted 2025-09-20 · ✦ hep-ex

Broadband interferometry-based searches for photon-axion conversion in vacuum

Josep Maria Batllori , Dieter Horns , Marios Maroudas This is my paper

Pith reviewed 2026-05-18 15:37 UTC · model grok-4.3

classification ✦ hep-ex
keywords photon-axion conversioninterferometryFabry-Pérot cavityPrimakoff effectWISP searchvacuum experimentaxion sensitivityMach-Zehnder interferometer
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The pith

A vacuum Mach-Zehnder interferometer with a high-finesse cavity projects sensitivity to photon-axion couplings of 3.7×10^{-14} GeV^{-1} up to 380 μeV.

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

The paper introduces an experiment called WINTER that uses a free-space Mach-Zehnder interferometer to look for photon-axion conversion in a magnetic field placed in vacuum. One arm of the interferometer allows mixing via the Primakoff effect, and the resulting change in light amplitude is modulated by polarization to produce a detectable signal. The design adds a Fabry-Pérot cavity of finesse 10^5 inside the vacuum arm to increase the effective interaction length and reach lower coupling strengths. If the projected performance is realized, the setup can test the DFSZ model line over a continuous range of axion masses without assuming axions account for dark matter.

Core claim

The central claim is that the WINTER interferometer, incorporating an external magnetic field and vacuum in one arm along with a Fabry-Pérot cavity of finesse 10^5, will achieve photon-axion coupling sensitivities down to g_{aγγ} ≃ 3.7×10^{-14} GeV^{-1} for axion masses up to 380 μeV, reaching the DFSZ theoretical line through broadband detection of amplitude and polarization changes.

What carries the argument

The WISP Interferometer (WINTER), a Mach-Zehnder-type setup with photon-axion mixing in a vacuum arm via the Primakoff effect, enhanced by a Fabry-Pérot cavity of finesse 10^5 operated in vacuum to amplify the interaction.

If this is right

  • The search proceeds without any assumption that axions constitute dark matter.
  • The method covers a continuous mass range up to 380 μeV rather than discrete tuned frequencies.
  • Polarization modulation isolates the axion-induced amplitude shift from other effects.
  • The vacuum environment and cavity combination extends laboratory reach toward theoretically motivated coupling values.

Where Pith is reading between the lines

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

  • If vacuum operation succeeds, the same interferometric layout could be scaled or adapted to probe other weakly interacting slim particles.
  • The broadband character offers a complementary laboratory test that does not rely on astrophysical or cosmological production mechanisms.
  • A working prototype would allow direct comparison of sensitivity limits between interferometric and resonant cavity haloscope approaches in the same mass window.

Load-bearing premise

The Fabry-Pérot cavity with finesse of 10^5 can be operated stably in vacuum while preserving the low noise and high stability required for the projected sensitivity.

What would settle it

Measurement showing that the cavity finesse drops or noise rises above the design threshold when the Fabry-Pérot cavity is placed in vacuum, preventing the target coupling sensitivity from being reached.

Figures

Figures reproduced from arXiv: 2509.16725 by Dieter Horns, Josep Maria Batllori, Marios Maroudas.

Figure 1
Figure 1. Figure 1: FIG. 1. Schematic view of the experimental setup of WINTER using a free space MZI for broadband detection. In red, the [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Projected sensitivity for WINTER experiment and a [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Representation of the total losses in ppm (in blue) for WINTER experiment as a function of the beam waist at the [PITH_FULL_IMAGE:figures/full_fig_p011_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Representation of the finesse variation (in blue) for WINTER experiment as a function of the beam waist at the plane [PITH_FULL_IMAGE:figures/full_fig_p012_4.png] view at source ↗
read the original abstract

A novel experiment is introduced to detect photon-axion conversion independent of the dark-matter hypothesis in a broad mass-range called WISP Interferometer (WINTER). The setup consists of a free-space Mach-Zehnder-type interferometer incorporating an external magnetic field and vacuum in one of the arms, where photon-axion mixing occurs via the Primakoff effect and is detected through changes in amplitude. The expected axion-induced signal is then modulated by polarization changes. The experiment is designed to integrate a Fabry-P\'erot cavity with a finesse of $10^{5}$ that will be operated in a vacuum environment, significantly enhancing the sensitivity. It is projected to reach the DFSZ theoretical line with photon-axion coupling sensitivities down to $g_{a\gamma\gamma}\simeq 3.7\times10^{-14}$ $\text{GeV}^{-1}$ for axion masses up to 380 $\mu$eV.

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 proposes the WINTER experiment: a Mach-Zehnder interferometer with a magnetic field and vacuum in one arm to detect photon-axion conversion via the Primakoff effect. A Fabry-Pérot cavity of finesse 10^5 is included to enhance sensitivity, with the axion-induced signal modulated by polarization changes. The central claim is a projected reach of g_{aγγ} ≃ 3.7×10^{-14} GeV^{-1} for axion masses up to 380 μeV, sufficient to test the DFSZ line.

Significance. If the projected sensitivity can be realized, the result would be significant for axion searches by providing broadband coverage independent of the dark-matter hypothesis and by using interferometric readout rather than resonant conversion. The approach could complement existing helioscope and haloscope limits in the μeV mass range.

major comments (2)
  1. [Abstract] Abstract: the sensitivity projection g_{aγγ} ≃ 3.7×10^{-14} GeV^{-1} is stated without derivation, error budget, or explicit formula showing how the value follows from the cavity finesse of 10^5, magnetic-field strength, integration time, or shot-noise floor. No equation or calculation is supplied that would allow independent verification of the scaling with F/π.
  2. [Experimental Setup] Cavity and vacuum section: the projection assumes the Fabry-Pérot cavity maintains an effective finesse of 10^5 and remains shot-noise limited when operated at 10^{-6}–10^{-8} mbar. No measured vacuum-cavity data, outgassing model, thermal-drift analysis, or alignment-stability budget is provided to support that the vacuum environment introduces neither excess mirror losses nor additional amplitude/phase noise.
minor comments (2)
  1. Define the acronym WISP at first use and clarify the distinction between WISP and WINTER.
  2. Figure captions should explicitly state the assumed integration time, magnetic-field strength, and noise model used to generate the projected sensitivity curve.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading and constructive comments on our manuscript. We address each major point below and have revised the manuscript to improve transparency and support for the projections.

read point-by-point responses

  1. Referee: [Abstract] Abstract: the sensitivity projection g_{aγγ} ≃ 3.7×10^{-14} GeV^{-1} is stated without derivation, error budget, or explicit formula showing how the value follows from the cavity finesse of 10^5, magnetic-field strength, integration time, or shot-noise floor. No equation or calculation is supplied that would allow independent verification of the scaling with F/π.

    Authors: We agree that the abstract would benefit from an explicit indication of the scaling. The projected sensitivity follows from the cavity-enhanced effective interaction length scaling as F/π, combined with the applied magnetic field, integration time, and shot-noise floor. In the revised manuscript we have added a concise statement of this scaling to the abstract together with a reference to the full derivation and error budget now summarized in the main text. revision: yes

  2. Referee: [Experimental Setup] Cavity and vacuum section: the projection assumes the Fabry-Pérot cavity maintains an effective finesse of 10^5 and remains shot-noise limited when operated at 10^{-6}–10^{-8} mbar. No measured vacuum-cavity data, outgassing model, thermal-drift analysis, or alignment-stability budget is provided to support that the vacuum environment introduces neither excess mirror losses nor additional amplitude/phase noise.

    Authors: The referee correctly notes that the sensitivity projection rests on the assumption that a finesse of 10^5 can be maintained in the stated vacuum range without excess losses or noise. As this is a proposed experiment, no measured data for the final WINTER apparatus exist at present. We have revised the manuscript to include a dedicated discussion of the expected vacuum performance, drawing on standard outgassing models and alignment budgets reported for comparable high-finesse cavities in the literature, and we explicitly flag that these assumptions will be validated experimentally during commissioning. revision: partial

Circularity Check

0 steps flagged

No circularity: sensitivity projection uses standard scaling with stated design assumptions

full rationale

The manuscript calculates projected reach by applying the known Primakoff conversion probability scaled by the cavity enhancement factor F/π (with F=10^5 given as a design target). This is a forward projection from first-principles formulas and an assumed performance level, not a fit to data that is then relabeled as a prediction. No equation reduces to its own output by construction, no self-citation supplies a load-bearing uniqueness theorem, and the vacuum-cavity operation is presented as an engineering requirement rather than a result derived from the sensitivity claim itself. The derivation chain is therefore self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The sensitivity projection depends on unverified assumptions about cavity performance and noise in vacuum; the paper introduces no new free parameters beyond the stated design choice of finesse 10^5.

free parameters (1)
  • Fabry-Pérot cavity finesse
    Design parameter chosen by hand to reach the stated sensitivity projection.
axioms (1)
  • domain assumption Photon-axion mixing occurs via the Primakoff effect in an external magnetic field
    Invoked to explain signal generation in the interferometer arm.

pith-pipeline@v0.9.0 · 5691 in / 1418 out tokens · 43332 ms · 2026-05-18T15:37:10.277590+00:00 · methodology

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Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

  • IndisputableMonolith/Foundation/RealityFromDistinction.lean reality_from_one_distinction unclear
    ?
    unclear

    Relation between the paper passage and the cited Recognition theorem.

    The experiment is designed to integrate a Fabry-Pérot cavity with a finesse of 10^5 that will be operated in a vacuum environment, significantly enhancing the sensitivity. It is projected to reach the DFSZ theoretical line with photon-axion coupling sensitivities down to g_aγγ ≃ 3.7×10^{-14} GeV^{-1}

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matches
The paper's claim is directly supported by a theorem in the formal canon.
supports
The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
extends
The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
uses
The paper appears to rely on the theorem as machinery.
contradicts
The paper's claim conflicts with a theorem or certificate in the canon.
unclear
Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.

Reference graph

Works this paper leans on

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    limit is also shown in gray. The specific parameters used for the calculation of both setups are shown in Tab. I. Note that the differences in the cutoff axion masses between the prototype and the full WINTER setup are due to the differ- ent wavelengths and magnet length along which the FPC is integrated. Parameter WINTER-prototype WINTER B ext 1.2 T 9 T ...

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    Sideband Amplitude Contribution The upper(+) and lower(-) sideband contribution for the sensitive and reference arms is given by: Esid,(±),S =± βmE0 2i √ 2 (1−P γ→a)e i[(ωγ+ωm)t−ϕ± S ], (35) Esid,(±),R =± βmE0 2 √ 2 ei[(ωγ+ωm)t−ϕ± R], (36) where the phase contributions for each arm are: ϕ± S = (kγ ±k m) L+ ∆L 2 ϕ± R = (kγ ±k m) L− ∆L 2 (37) The total side...

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