Pith. sign in

REVIEW 4 major objections 4 minor 87 references

Muon bremsstrahlung from the secondary muon beam at neutrino experiments is a new production channel for heavy neutral leptons, reaching masses near 1 GeV where meson decays cannot reach.

Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →

Challenge this review Re-run · record.json Download PDF Read on arXiv ↗

T0 review · deepseek-v4-flash

2026-08-01 23:32 UTC pith:GRZMOQWC

load-bearing objection Worth refereeing: a genuinely new production channel at neutrino beam-dumps, but the sensitivity curves rest on an unvalidated muon flux and Eq. (8) has an acceptance sign error that needs fixing. the 4 major comments →

arxiv 2607.15368 v1 pith:GRZMOQWC submitted 2026-07-16 hep-ph

Muon Bremsstrahlung as a New Probe of Dark Sector at Neutrino Experiments

P. S. Bhupal Dev , Bhaskar Dutta , Aparajitha Karthikeyan , Mudit Rai , Zahra Tabrizi This is my paper
classification hep-ph
keywords muon bremsstrahlungheavy neutral leptonstau neutrino mixingbeam dumpneutrino experimentsdark sectorDUNE Near DetectorSBND
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved

The pith

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

This paper argues that a previously overlooked source of new physics exists at neutrino beam-dump facilities: the intense, focused muon beam produced alongside the neutrino beam in meson decays. When these muons hit the beam dump, they can radiate a new light particle through bremsstrahlung, which then decays into heavy neutral leptons (HNLs). Because the muon energy sets the kinematic reach rather than the fixed mass of a decaying meson, this mechanism can create HNLs beyond the reach of conventional meson-decay searches. Focusing on HNLs that mix only with tau neutrinos, the paper shows that DUNE's Near Detector and SBND could probe previously unexplored parameter space up to about 1 GeV through decay channels into a neutral pion, a muon pair, or an electron-positron pair, with distinctive forward kinematics.

Core claim

Muon bremsstrahlung—the radiation of a new muonphilic scalar by a muon scattering in the beam absorber—provides a new production mechanism for heavy neutral leptons at accelerator neutrino experiments. The authors demonstrate that the focused secondary muon beam, carrying roughly 0.1 muons per proton on target at the LBNF beamline with energies around 5–20 GeV, produces a substantial flux of scalars, and hence HNLs, when it impinges on the dump. With the scalar mass fixed at 2.1 times the HNL mass and the HNL mixing only with tau neutrinos, the HNL flux from this mechanism is independent of |UτN|², while the observable signal scales with it through the decay probability. Using this mechanism

What carries the argument

The central object is the focused muon flux at the beam dump, obtained by simulating two-body meson decays in the decay pipe and collecting muons that reach the absorber. The paper folds this flux with the differential muon bremsstrahlung cross section to compute the scalar flux, then treats the scalar as decaying promptly into HNLs with a fixed mass ratio mφ = 2.1 mN. The HNL detection probability is governed by the decay length, set by both weak mixing and the muonphilic scalar coupling. The production is independent of the HNL mixing angle, so the observable rate scales directly with |UτN|², making the sensitivity prediction transparent.

Load-bearing premise

The results rely on the modeled focused muon flux at the dump—roughly 0.1 muons per proton on target for LBNF and the BNB analog, with all muons treated as collinear—and if that flux is lower than assumed, every predicted event rate and sensitivity contour scales down proportionally.

What would settle it

A measurement or realistic simulation of the muon flux at the beam dump of LBNF or BNB would settle the claim: if the number of muons reaching the absorber with energies above about 5 GeV is substantially below the assumed ~0.1 per proton on target, the projected sensitivity regions in the paper's Fig. 3 would shrink or disappear. More directly, a dedicated search at DUNE ND for forward single-π⁰, μ⁺μ⁻, or e⁺e⁻ events that cannot be explained by neutrino interactions would test the mechanism experimentally.

Watch this falsifier — get emailed when new claim-graph text bears on it.

If this is right

  • DUNE Near Detector can probe HNL masses up to about 1 GeV in the νπ⁰, νμ⁺μ⁻, and νe⁺e⁻ channels, entering previously unexplored parameter space for tau-mixing HNLs.
  • SBND and MiniBooNE can begin to probe new parameter space in the single-π⁰ channel at lower HNL masses.
  • The signal is forward and high-energy, allowing background suppression via simple cuts such as total transverse momentum below 125 MeV, small opening angles, and energy thresholds around 3 GeV.
  • Three-body kaon decays contribute to scalar production for mφ below about 370 MeV, but muon bremsstrahlung extends the reach to heavier scalars because the relevant energy scale is the muon energy rather than a fixed hadron mass.
  • The muon-bremsstrahlung mechanism is independent of the HNL mixing angle, meaning that the same flux calculation applies for any mixing flavor assumption.

Where Pith is reading between the lines

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

  • If this mechanism is correct, the same muon-bremsstrahlung setup at neutrino facilities could be repurposed to search for other muonphilic states, such as Lμ−Lτ gauge bosons or axion-like particles, and could be extended to elastic or inelastic dark matter scenarios.
  • The sensitivity curves depend critically on the assumed muon flux; a direct measurement of the focused muon flux at the LBNF and BNB beam dumps—or a dedicated simulation validated against data—would test the central prediction and refine the projections.
  • Treating all muons within the absorber acceptance as perfectly collinear likely overestimates the forward flux of scalars; including the finite angular spread of the muon beam would yield a more conservative but more robust sensitivity estimate.
  • At HNL masses above roughly 500 MeV, where two-body meson decays are kinematically suppressed, the muon-bremsstrahlung mechanism could be the only production channel available at these facilities, regardless of the HNL's flavor mixing pattern.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

4 major / 4 minor

Summary. The paper proposes that muon bremsstrahlung from the intense secondary muon beam at neutrino beam-dump facilities constitutes a new production mechanism for dark-sector particles. As a benchmark, the authors consider a muonphilic scalar φ that decays to heavy neutral leptons (HNLs), and compute HNL production from muon bremsstrahlung in the absorber at the BNB and LBNF beamlines. They estimate sensitivities for SBND, MiniBooNE, ICARUS, and DUNE ND to HNL decays into νπ0, νμ+μ−, and νe+e− final states, and claim reach up to mN ~ 1 GeV and previously unexplored |UτN|2 parameter space. The signal chain—muon flux, scalar bremsstrahlung, scalar decay to HNLs, HNL propagation, and detector decay—is modeled end-to-end with a Monte Carlo simulation.

Significance. If the muon-flux modeling and the acceptance calculation hold up, the paper would introduce a genuinely new production channel for HNLs and other dark-sector particles at existing and upcoming neutrino facilities, complementing meson-decay and proton-bremsstrahlung channels. The kinematic signatures are plausibly distinct from neutrino-induced backgrounds, and the authors use published matrix elements and decay widths for the HNL interactions. The main significance risk is quantitative: every sensitivity contour is proportional to the modeled muon flux, which is not validated against an official beam simulation or data and is treated as fully collinear; a factor-of-few error would shrink or eliminate the claimed new parameter space.

major comments (4)
  1. [HNL Detection, Eq. (8)] The acceptance step function has the wrong sign. The text states the signal consists of HNLs 'directed towards' the detector, and θ_det denotes the detector's angular half-aperture; the physical condition is θ_N < θ_det, i.e., Θ(θ_det − θ_N). As written, Θ(θ_N − θ_det) counts only HNLs that miss the detector. If implemented literally, this would massively overcount events and shift all Fig. 3 contours. This must be corrected and the numerical results re-run.
  2. [Scalar Production and End Matter A, Eq. (3)] The muon flux is the most load-bearing input and is not validated. For LBNF it is 'modeled following Refs. [14,16]' with no comparison to a public LBNF beam simulation or data; for BNB, RKHorn is used without a published cross-check. The paper reports ~0.1 muons/POT but gives no uncertainty estimate. Since the HNL yield and all sensitivity contours scale linearly with dNμ/dEμ, a factor-of-2–3 uncertainty directly changes the claimed reach. Please provide validation plots or a conservative band showing the impact of the flux uncertainty, especially in the regions where the projected contours approach existing bounds.
  3. [Scalar Production, after Eq. (3)] After integrating the muon flux over the absorber acceptance, all muons are treated as collinear (θμ = 0). This maximizes the forward scalar flux and hence the HNL flux reaching the small-angle detectors. A realistic finite angular spread of the muon beam, even within the absorber acceptance, will reduce the effective forward flux. Please quantify the effect of the muon angular distribution on the final event counts, or justify with a dedicated check that the collinear approximation is accurate at the percent-to-tens-of-percent level.
  4. [Eq. (3) and λμ] The effective path length λμ(Eμ) is defined as the distance over which a muon loses 10% of its energy. Using this as the production length for bremsstrahlung is an order-of-magnitude approximation, especially for hard emissions with x = Eφ/Eμ not small. The paper should clarify whether this is intended as a conservative one-interaction-length estimate, and ideally compare with a more standard treatment using the full muon energy-loss trajectory.
minor comments (4)
  1. [Eq. (5)] The notation d²BR/dEN dcosθN is not a branching ratio; it appears to be the differential HNL yield per decaying scalar. Please rename to avoid confusion, e.g., d²Γ/(Γ dEN dcosθN) or an explicit differential yield.
  2. [Sensitivities, first paragraph] The sentence 'for ICARUS, MiniBooNE and ICARUS, only the 2.3 event contours are shown' lists ICARUS twice. Also confirm the ordering in the Fig. 3 caption ('BB, IC' vs. 'MB, IC') is consistent.
  3. [End Matter C, SBND/MiniBooNE/ICARUS backgrounds] The paper states that no detailed background analysis is performed for these detectors and relies on a kinematic separation argument. This is acceptable for a phenomenology letter, but it should be clearly listed as a limitation in the main text, not only in the End Matter.
  4. [Figure 3 caption] The left panel is labeled 'νπ0' in the text but 'single π0' in the caption; use a single convention throughout.

Circularity Check

0 steps flagged

No significant circularity: the sensitivity contours are forward calculations from an external Weizsäcker-Williams bremsstrahlung cross section, published HNL widths, and benchmark couplings; the main caveats (unvalidated muon flux, Eq. (8) acceptance sign, no dedicated background study for SBND/MB/IC) are validation/correctness concerns, not input-output identity.

full rationale

The derivation chain is not circular. Eq. (3) evaluates the scalar flux by folding a modeled muon flux with the external Weizsäcker-Williams bremsstrahlung cross section from Ref. [62]; Eq. (5) convolves this with scalar decay kinematics; Eqs. (6)-(8) use published HNL widths (Refs. [46,66-68]) plus the model's scalar-mediated width. The final |UτN|^2 contours are solved as forward predictions for fixed event-number benchmarks (2.3/10/100 events), not fitted to any target result. The muon flux is an input, adopted from RKHorn (BNB) and, for LBNF, from a focused-beam model 'following Refs. [14,16]'; those references are co-authored self-citations, but they supply a boundary condition, not the predicted quantity, and no uniqueness theorem or definitional identity equates the input flux with the output HNL reach. The benchmark choices (mφ/mN = 2.1, yµ saturated to external NA64µ/BaBar/CMS bounds, BR(φ→NN) ≈ 90%) are model assumptions, not fits to the predicted contours. Robustness caveats exist and are partly acknowledged in the paper: the LBNF/BNB muon flux is not validated against an official beam simulation or assigned an uncertainty; End Matter C states that for SBND/MiniBooNE/ICARUS 'We do not perform a detailed signal versus background analysis' and instead 'predict[s]' near-background-free sensitivity; and Eq. (8)'s acceptance factor Θ(θ_N − θ_det) appears to have the inequality reversed relative to the physical θ_N < θ_det. These are correctness and validation concerns, and possibly an internal sign error, but none of them makes a predicted quantity equal by construction to an input. Therefore no circular step is exhibited, and the circularity score is 0.

Axiom & Free-Parameter Ledger

3 free parameters · 6 axioms · 0 invented entities

The paper introduces no new particles: the muonphilic scalar and HNL are pre-existing benchmark constructions. The load-bearing freedom is concentrated in four benchmark choices — yµ, yN, mφ/mN, and τ-only mixing — plus the modeled muon flux at the dump. These are not fitted to data, but they determine the normalization and shape of every sensitivity curve.

free parameters (3)
  • yµ (muon Yukawa coupling) = ~[8×10⁻⁴, 2×10⁻³] for mφ from 10 MeV to 5 GeV
    Set to saturate invisible-scalar bounds from NA64µ, BaBar 4µ, and CMS 4µ. Controls the entire scalar production rate via d²Nφ ∝ yµ².
  • yN (HNL Yukawa coupling) = yN ≳ 10 yµ
    Chosen so that BR(φ→NN) ≈ 90%. Controls the scalar decay length (Eq. 4) and the HNL decay width through the mediator (Eq. 7).
  • mφ/mN mass ratio = 2.1
    Adopted by hand for the entire analysis. This ratio fixes the kinematic relation between the scalar and HNL and directly sets the plotted x-axis mN = mφ/2.1.
axioms (6)
  • standard math Weizsäcker-Williams muon-bremsstrahlung cross section from Ref. [62] is valid in the absorber material with target nuclei density ndump = NAρ/A.
    Invoked in Eq. (3) for all scalar fluxes; no validation against alternate bremsstrahlung calculations is shown.
  • domain assumption Focused meson fluxes from RKHorn (BNB) and from the model in Refs. [14,16] (LBNF) accurately reproduce the muon flux reaching the absorber.
    The entire yield calculation starts from these muon fluxes; no comparison to data or uncertainty estimate is provided.
  • domain assumption Muons satisfying the absorber acceptance can be treated as collinear (θµ = 0) and the angular dependence of the bremsstrahlung cross section can be neglected.
    Stated explicitly in Scalar Production; this simplification affects the scalar angular distribution and hence the fraction of HNLs pointing toward the detector.
  • domain assumption The HNL mixes only with the tau neutrino: |UτN| ≠ 0, |UeN| = |UµN| = 0.
    Motivated by the 3σ allowed range of normal ordering, but it suppresses all standard meson-decay HNL production and is therefore essential to the claim that muon bremsstrahlung dominates.
  • standard math Published HNL decay widths and branching ratios from Refs. [46,66–68] apply, and the scalar-mediated decay width scales as |UαN|²(yµ yN/mφ²)².
    Used in Eq. (7) and Fig. 5 to compute the HNL decay length and final-state branching ratios.
  • domain assumption Existing constraints from CHARM, BEBC, BaBar, ArgoNeuT, DELPHI, and BBN can be straightforwardly applied to this model.
    The authors themselves note that the added muonphilic scalar can modify the BBN constraints and show those bounds as dashed lines, acknowledging that this assumption is not fully quantified.

pith-pipeline@v1.3.0-alltime-deepseek · 14066 in / 13968 out tokens · 143206 ms · 2026-08-01T23:32:42.404612+00:00 · methodology

0 comments
read the original abstract

We show that muon bremsstrahlung provides a new production mechanism for light new physics at accelerator neutrino experiments. The intense, highly collimated muon beam produced alongside the neutrino beam in meson decays provides a powerful source for the bremsstrahlung production of new physics when it impinges on the beam dump at these facilities. As a benchmark scenario, we consider a muonphilic scalar coupled to Heavy Neutral Leptons (HNLs) and show that muon bremsstrahlung enables the production of HNLs with masses beyond the kinematic reach of meson decays. Using this new production mechanism and focusing on HNL mixing with tau neutrinos, we find that ongoing (upcoming) short-baseline experiments like SBND (DUNE Near Detector) can probe previously unexplored parameter space for HNL masses up to $\mathcal{O}(1)~\mathrm{GeV}$ through their decay into pions, $\mu^+\mu^-$, and $e^+e^-$ final states at the detector. The resulting signals exhibit distinctive kinematics, allowing efficient discrimination from neutrino-induced Standard Model backgrounds. Our results demonstrate that the muon bremsstrahlung mechanism substantially extends the discovery potential of accelerator neutrino experiments for HNLs and other dark sector particles.

Figures

Figures reproduced from arXiv: 2607.15368 by Aparajitha Karthikeyan, Bhaskar Dutta, Mudit Rai, P. S. Bhupal Dev, Zahra Tabrizi.

Figure 1
Figure 1. Figure 1: Schematic sketch (not to scale) showing the muon bremsstrahlung production of scalars ( [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: The number of HNLs that are directed towards [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: HNL sensitivity at DUNE ND, SBND, MiniBooNE (MB), and ICARUS (IC) in the [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Muon flux that reaches the dump at the BNB [PITH_FULL_IMAGE:figures/full_fig_p008_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Relevant branching ratios of the HNL to e +e −, π 0 and µ +µ −. C. Signal vs. Background To show how the SM backgrounds can affect our sensitivity analysis, for the DUNE ND we show in [PITH_FULL_IMAGE:figures/full_fig_p009_5.png] view at source ↗

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

87 extracted references · 63 linked inside Pith

  1. [1]

    A. A. Aguilar-Arevaloet al.(MiniBooNE), The Mini- BooNE Detector, Nucl. Instrum. Meth. A599, 28 (2009), arXiv:0806.4201 [hep-ex]

    Pith/arXiv arXiv 2009

  2. [2]

    R. Acciarriet al.(MicroBooNE, LAr1-ND, ICARUS- W A104), A Proposal for a Three Detector Short-Baseline Neutrino Oscillation Program in the Fermilab Booster Neutrino Beam, (2015), arXiv:1503.01520 [physics.ins- det]

    arXiv 2015

  3. [3]

    Alvarez Garrote (SBND), Status of the Short-Baseline Near Detector at Fermilab, PoSICHEP2024, 135 (2025), arXiv:2501.11349 [hep-ex]

    R. Alvarez Garrote (SBND), Status of the Short-Baseline Near Detector at Fermilab, PoSICHEP2024, 135 (2025), arXiv:2501.11349 [hep-ex]

    Pith/arXiv arXiv 2025

  4. [4]

    Amerioet al.(ICARUS), Design, construction and tests of the ICARUS T600 detector, Nucl

    S. Amerioet al.(ICARUS), Design, construction and tests of the ICARUS T600 detector, Nucl. Instrum. Meth. A527, 329 (2004)

    2004

  5. [5]

    R. Acciarriet al.(DUNE), Long-Baseline Neutrino Facil- ity (LBNF) and Deep Underground Neutrino Experiment (DUNE): Conceptual Design Report, Volume 1: The LBNF and DUNE Projects, (2016), arXiv:1601.05471 [physics.ins-det]

    arXiv 2016

  6. [6]

    Heweset al.(DUNE), Deep Underground Neutrino Experiment (DUNE) Near Detector Conceptual De- sign Report, Instruments5, 31 (2021), arXiv:2103.13910 [physics.ins-det]

    V. Heweset al.(DUNE), Deep Underground Neutrino Experiment (DUNE) Near Detector Conceptual De- sign Report, Instruments5, 31 (2021), arXiv:2103.13910 [physics.ins-det]

    arXiv 2021

  7. [7]

    Iltenet al., Experiments and Facilities for Accelerator- Based Dark Sector Searches, inSnowmass 2021(2022) arXiv:2206.04220 [hep-ex]

    P. Iltenet al., Experiments and Facilities for Accelerator- Based Dark Sector Searches, inSnowmass 2021(2022) arXiv:2206.04220 [hep-ex]

    Pith/arXiv arXiv 2021

  8. [8]

    Batell, N

    B. Batell, N. Blinov, C. Hearty, and R. McGehee, Explor- ing Dark Sector Portals with High Intensity Experiments, inSnowmass 2021(2022) arXiv:2207.06905 [hep-ph]

    Pith/arXiv arXiv 2021

  9. [9]

    Goriet al., Dark Sector Physics at High-Intensity Ex- periments, inSnowmass 2021(2022) arXiv:2209.04671 [hep-ph]

    S. Goriet al., Dark Sector Physics at High-Intensity Ex- periments, inSnowmass 2021(2022) arXiv:2209.04671 [hep-ph]

    Pith/arXiv arXiv 2021

  10. [10]

    Batell, J

    B. Batell, J. Berger, and A. Ismail, Probing the Higgs Por- tal at the Fermilab Short-Baseline Neutrino Experiments, Phys. Rev. D100, 115039 (2019), arXiv:1909.11670 [hep- ph]

    arXiv 2019

  11. [11]

    J. M. Berryman, A. de Gouvea, P. J. Fox, B. J. Kayser, K. J. Kelly, and J. L. Raaf, Searches for Decays of New Particles in the DUNE Multi-Purpose Near Detector, JHEP02, 174, arXiv:1912.07622 [hep-ph]

    Pith/arXiv arXiv 1912

  12. [12]

    Dutta, D

    B. Dutta, D. Kim, A. Thompson, R. T. Thornton, and R. G. Van de Water, Solutions to the MiniBooNE Anomaly from New Physics in Charged Meson Decays, Phys. Rev. Lett.129, 111803 (2022), arXiv:2110.11944 [hep-ph]

    Pith/arXiv arXiv 2022

  13. [13]

    Abratenkoet al.(MicroBooNE), Search for long-lived heavy neutral leptons and Higgs portal scalars decaying in the MicroBooNE detector, Phys

    P. Abratenkoet al.(MicroBooNE), Search for long-lived heavy neutral leptons and Higgs portal scalars decaying in the MicroBooNE detector, Phys. Rev. D106, 092006 (2022), arXiv:2207.03840 [hep-ex]

    Pith/arXiv arXiv 2022

  14. [14]

    P. S. B. Dev, B. Dutta, T. Han, and D. Kim, Anomalous tau neutrino appearance from light mediators in short- baseline neutrino experiments, Phys. Lett. B850, 138500 (2024), arXiv:2304.02031 [hep-ph]

    Pith/arXiv arXiv 2024

  15. [15]

    Batell, W

    B. Batell, W. Huang, and K. J. Kelly, Keeping it simple: simplified frameworks for long-lived particles at neutrino facilities, JHEP08, 092, arXiv:2304.11189 [hep-ph]

    Pith/arXiv arXiv

  16. [16]

    Dutta, A

    B. Dutta, A. Karthikeyan, and D. Kim, Longer-lived mediators from charged mesons and photons at neu- trino experiments, Phys. Rev. D109, 075029 (2024), arXiv:2308.01491 [hep-ph]

    Pith/arXiv arXiv 2024

  17. [17]

    Brdar, B

    V. Brdar, B. Dutta, W. Jang, D. Kim, I. M. Shoemaker, Z. Tabrizi, A. Thompson, and J. Yu, Axionlike Parti- cles at Future Neutrino Experiments: Closing the Cos- mological Triangle, Phys. Rev. Lett.126, 201801 (2021), arXiv:2011.07054 [hep-ph]

    Pith/arXiv arXiv 2021

  18. [18]

    Dutta, D

    B. Dutta, D. Goswami, A. Karthikeyan, and K. J. Kelly, Dirt/Detector/Dump: complementary BSM production at Short-Baseline Neutrino Facilities, JHEP05, 240, arXiv:2501.09840 [hep-ph]

    Pith/arXiv arXiv

  19. [19]

    Dutta, D

    B. Dutta, D. Goswami, and A. Karthikeyan, Monopho- tons from scalar portal dark matter at neutrino experi- ments, JHEP02, 142, arXiv:2507.07936 [hep-ph]

    arXiv

  20. [20]

    Foroughi-Abari and A

    S. Foroughi-Abari and A. Ritz, Dark sector production via proton bremsstrahlung, Phys. Rev. D105, 095045 (2022), arXiv:2108.05900 [hep-ph]

    Pith/arXiv arXiv 2022

  21. [21]

    Foroughi-Abari, P

    S. Foroughi-Abari, P. Reimitz, and A. Ritz, Closer look at dark vector splitting functions in proton bremsstrahlung, Phys. Rev. D112, 015030 (2025), arXiv:2409.09123 [hep- ph]

    Pith/arXiv arXiv 2025

  22. [22]

    Kling, P

    F. Kling, P. Reimitz, and A. Ritz, Dark vector bo- son bremsstrahlung: New form factors for a broader class of models, Phys. Rev. D113, 015008 (2026), arXiv:2509.09437 [hep-ph]

    arXiv 2026

  23. [23]

    Blumlein and J

    J. Blumlein and J. Brunner, New Exclusion Limits for Dark Gauge Forces from Beam-Dump Data, Phys. Lett. B701, 155 (2011), arXiv:1104.2747 [hep-ex]

    Pith/arXiv arXiv 2011

  24. [24]

    J. B. Dent, B. Dutta, D. Kim, S. Liao, R. Mahapatra, K. Sinha, and A. Thompson, New Directions for Axion Searches via Scattering at Reactor Neutrino Experiments, Phys. Rev. Lett.124, 211804 (2020), arXiv:1912.05733 [hep-ph]

    Pith/arXiv arXiv 2020

  25. [25]

    Blinov, P

    N. Blinov, P. J. Fox, K. J. Kelly, P. A. N. Machado, and R. Plestid, Dark fluxes from electromagnetic cascades, JHEP07, 022, arXiv:2401.06843 [hep-ph]

    Pith/arXiv arXiv

  26. [26]

    Tsai, AXION BREMSSTRAHLUNG BY AN ELECTRON BEAM, Phys

    Y.-S. Tsai, AXION BREMSSTRAHLUNG BY AN ELECTRON BEAM, Phys. Rev. D34, 1326 (1986)

    1986

  27. [27]

    Tsai, PRODUCTION OF NEUTRAL BOSONS BY AN ELECTRON BEAM, Phys

    Y.-S. Tsai, PRODUCTION OF NEUTRAL BOSONS BY AN ELECTRON BEAM, Phys. Rev. D40, 760 (1989)

    1989

  28. [28]

    Rella, B

    C. Rella, B. D¨ obrich, and T.-T. Yu, Searching for muon- philic dark sectors with proton beams, Phys. Rev. D106, 035023 (2022), arXiv:2205.09870 [hep-ph]

    Pith/arXiv arXiv 2022

  29. [29]

    C.-Y. Chen, J. Kozaczuk, and Y.-M. Zhong, Exploring leptophilic dark matter with NA64-µ, JHEP10, 154, arXiv:1807.03790 [hep-ph]. 7

    Pith/arXiv arXiv

  30. [30]

    Y. M. Andreevet al.(NA64), First Results in the Search for Dark Sectors at NA64 with the CERN SPS High En- ergy Muon Beam, Phys. Rev. Lett.132, 211803 (2024), arXiv:2401.01708 [hep-ex]

    Pith/arXiv arXiv 2024

  31. [31]

    Ahdidaet al.(SHiP), The SHiP experiment at the proposed CERN SPS Beam Dump Facility, Eur

    C. Ahdidaet al.(SHiP), The SHiP experiment at the proposed CERN SPS Beam Dump Facility, Eur. Phys. J. C82, 486 (2022), arXiv:2112.01487 [physics.ins-det]

    Pith/arXiv arXiv 2022

  32. [32]

    Apyanet al., DarkQuest: A dark sector upgrade to SpinQuest at the 120 GeV Fermilab Main Injector, in Snowmass 2021(2022) arXiv:2203.08322 [hep-ex]

    A. Apyanet al., DarkQuest: A dark sector upgrade to SpinQuest at the 120 GeV Fermilab Main Injector, in Snowmass 2021(2022) arXiv:2203.08322 [hep-ex]

    Pith/arXiv arXiv 2021

  33. [33]

    Blinov, S

    N. Blinov, S. Gori, and N. Hamer, Diphoton signals of muon-philic scalars at DarkQuest, Phys. Rev. D110, 075006 (2024), arXiv:2405.17651 [hep-ph]

    Pith/arXiv arXiv 2024

  34. [34]

    Blinov, P

    N. Blinov, P. J. Fox, K. J. Kelly, R. Plestid, and T. Zhou, Lµ −L τ gauge bosons in beam dumps and supernovae, JHEP06, 155, arXiv:2511.09619 [hep-ph]

    Pith/arXiv arXiv

  35. [35]

    Minkowski,µ→eγat a Rate of One Out of 10 9 Muon Decays?, Phys

    P. Minkowski,µ→eγat a Rate of One Out of 10 9 Muon Decays?, Phys. Lett. B67, 421 (1977)

    1977

  36. [36]

    R. N. Mohapatra and G. Senjanovic, Neutrino Mass and Spontaneous Parity Nonconservation, Phys. Rev. Lett. 44, 912 (1980)

    1980

  37. [37]

    Gell-Mann, P

    M. Gell-Mann, P. Ramond, and R. Slansky, Complex Spinors and Unified Theories, Conf. Proc. C790927, 315 (1979), arXiv:1306.4669 [hep-th]

    Pith/arXiv arXiv 1979

  38. [38]

    Yanagida, Horizontal gauge symmetry and masses of neutrinos, Conf

    T. Yanagida, Horizontal gauge symmetry and masses of neutrinos, Conf. Proc. C7902131, 95 (1979)

    1979

  39. [39]

    Asaka, S

    T. Asaka, S. Eijima, and A. Watanabe, Heavy neutrino search in accelerator-based experiments, JHEP03, 125, arXiv:1212.1062 [hep-ph]

    Pith/arXiv arXiv

  40. [40]

    K. J. Kelly and P. A. N. Machado, MicroBooNE experi- ment, NuMI absorber, and heavy neutral leptons, Phys. Rev. D104, 055015 (2021), arXiv:2106.06548 [hep-ph]

    Pith/arXiv arXiv 2021

  41. [41]

    Abratenkoet al.(MicroBooNE), Search for Heavy Neu- tral Leptons in Electron-Positron and Neutral-Pion Final States with the MicroBooNE Detector, Phys

    P. Abratenkoet al.(MicroBooNE), Search for Heavy Neu- tral Leptons in Electron-Positron and Neutral-Pion Final States with the MicroBooNE Detector, Phys. Rev. Lett. 132, 041801 (2024), arXiv:2310.07660 [hep-ex]

    Pith/arXiv arXiv 2024

  42. [42]

    G. F. S. Alves, P. S. B. Dev, K. J. Kelly, and P. A. N. Machado, Mass reconstruction of heavy neutral leptons from stopped mesons, Phys. Rev. D111, 015017 (2025), arXiv:2409.04394 [hep-ph]

    Pith/arXiv arXiv 2025

  43. [43]

    J. L. Feng, A. Hewitt, F. Kling, and D. La Rocco, Sim- ulating heavy neutral leptons with general couplings at collider and fixed target experiments, Phys. Rev. D110, 035029 (2024), arXiv:2405.07330 [hep-ph]

    Pith/arXiv arXiv 2024

  44. [44]

    Hostert and S

    M. Hostert and S. Urrea, Long-Lived Particles from Me- son and Muon Decays at Rest at Spallation Sources, (2025), arXiv:2509.14085 [hep-ph]

    arXiv 2025

  45. [45]

    Ballett, M

    P. Ballett, M. Hostert, and S. Pascoli, Dark Neutrinos and a Three Portal Connection to the Standard Model, Phys. Rev. D101, 115025 (2020), arXiv:1903.07589 [hep-ph]

    Pith/arXiv arXiv 2020

  46. [46]

    Capozzi, B

    F. Capozzi, B. Dutta, G. Gurung, W. Jang, I. M. Shoemaker, A. Thompson, and J. Yu, Enhancing the sensitivity to seesaw mechanism predictions in gauged B-L scenarios, Phys. Rev. D111, 055036 (2025), arXiv:2410.08981 [hep-ph]

    Pith/arXiv arXiv 2025

  47. [47]

    F. M. Burk, P. S. B. Dev, B. Dutta, T. Han, A. Karthikeyan, and D. Kim, Drell-Yan Production of New Particles at Fixed-Target Experiments: Heavy Neu- tral Lepton as a Case Study, (2026), arXiv:2601.18874 [hep-ph]

    arXiv 2026

  48. [48]

    A. M. Abdullahi, A. de Gouvˆ ea, B. Dutta, I. M. Shoe- maker, and Z. Tabrizi, Heavy Neutral Leptons via Ax- ionlike Particles at Neutrino Facilities, Phys. Rev. Lett. 133, 261802 (2024), arXiv:2311.07713 [hep-ph]

    Pith/arXiv arXiv 2024

  49. [49]

    Batell, A

    B. Batell, A. Freitas, A. Ismail, and D. Mckeen, Flavor- specific scalar mediators, Phys. Rev. D98, 055026 (2018), arXiv:1712.10022 [hep-ph]

    Pith/arXiv arXiv 2018

  50. [50]

    Dutta, S

    B. Dutta, S. Ghosh, and T. Li, Explaining (g−2) µ,e, the KOTO anomaly and the MiniBooNE excess in an extended Higgs model with sterile neutrinos, Phys. Rev. D102, 055017 (2020), arXiv:2006.01319 [hep-ph]

    Pith/arXiv arXiv 2020

  51. [51]

    Harris, P

    P. Harris, P. Schuster, and J. Zupan, Snowmass White Paper: New flavors and rich structures in dark sectors, in Snowmass 2021(2022) arXiv:2207.08990 [hep-ph]

    Pith/arXiv arXiv 2021

  52. [52]

    X.-G. He, G. C. Joshi, H. Lew, and R. R. Volkas, Simplest Z-prime model, Phys. Rev. D44, 2118 (1991)

    1991

  53. [53]

    Dutta, S

    B. Dutta, S. Ghosh, and J. Kumar, A sub-GeV dark matter model, Phys. Rev. D100, 075028 (2019), arXiv:1905.02692 [hep-ph]

    Pith/arXiv arXiv 2019

  54. [54]

    R. N. Mohapatra and J. W. F. Valle, Neutrino Mass and Baryon Number Nonconservation in Superstring Models, Phys. Rev. D34, 1642 (1986)

    1986

  55. [55]

    A. Atre, T. Han, S. Pascoli, and B. Zhang, The Search for Heavy Majorana Neutrinos, JHEP05, 030, arXiv:0901.3589 [hep-ph]

    Pith/arXiv arXiv

  56. [56]

    de Gouvˆ ea and A

    A. de Gouvˆ ea and A. Kobach, Global Constraints on a Heavy Neutrino, Phys. Rev. D93, 033005 (2016), arXiv:1511.00683 [hep-ph]

    Pith/arXiv arXiv 2016

  57. [57]

    Chrzaszcz, M

    M. Chrzaszcz, M. Drewes, T. E. Gonzalo, J. Harz, S. Kr- ishnamurthy, and C. Weniger, A frequentist analysis of three right-handed neutrinos with GAMBIT, Eur. Phys. J. C80, 569 (2020), arXiv:1908.02302 [hep-ph]

    Pith/arXiv arXiv 2020

  58. [58]

    P. D. Bolton, F. F. Deppisch, and P. S. Bhupal Dev, Neu- trinoless double beta decay versus other probes of heavy sterile neutrinos, JHEP03, 170, arXiv:1912.03058 [hep- ph]

    Pith/arXiv arXiv 1912

  59. [59]

    Fern´ andez-Mart ´ ınez, M

    E. Fern´ andez-Mart ´ ınez, M. Gonz´ alez-L´ opez, J. Hern´ andez-Garc ´ ıa, M. Hostert, and J. L´ opez-Pav´ on, Effective portals to heavy neutral leptons, JHEP09, 001, arXiv:2304.06772 [hep-ph]

    Pith/arXiv arXiv

  60. [60]

    Drewes, J

    M. Drewes, J. Klari´ c, and J. L´ opez-Pav´ on, New bench- mark models for heavy neutral lepton searches, Eur. Phys. J. C82, 1176 (2022), arXiv:2207.02742 [hep-ph]

    Pith/arXiv arXiv 2022

  61. [61]

    Thompson, Rkhorn (2024), Available at https://github.com/athompson-git/RKHorn

    A. Thompson, Rkhorn (2024), Available at https://github.com/athompson-git/RKHorn

    2024

  62. [62]

    Sieber, D

    H. Sieber, D. V. Kirpichnikov, I. V. Voronchikhin, P. Crivelli, S. N. Gninenko, M. M. Kirsanov, N. V. Kras- nikov, L. Molina-Bueno, and S. K. Sekatskii, Probing hid- den sectors with a muon beam: Implication of spin-0 dark matter mediators for the muon (g-2) anomaly and the va- lidity of the Weisz¨ acker-Williams approach, Phys. Rev. D 108, 056018 (2023),...

    Pith/arXiv arXiv 2023

  63. [63]

    Navaset al.(Particle Data Group), Review of particle physics, Phys

    S. Navaset al.(Particle Data Group), Review of particle physics, Phys. Rev. D110, 030001 (2024)

    2024

  64. [64]

    J. P. Leeset al.(BaBar), Search for a muonic dark force at BABAR, Phys. Rev. D94, 011102 (2016), arXiv:1606.03501 [hep-ex]

    Pith/arXiv arXiv 2016

  65. [65]

    A. Hayrapetyanet al.(CMS), Model-independent search for pair production of new bosons decaying into muons in proton-proton collisions at √s= 13 TeV, JHEP12, 172, arXiv:2407.20425 [hep-ex]

    Pith/arXiv arXiv

  66. [66]

    Bondarenko, A

    K. Bondarenko, A. Boyarsky, D. Gorbunov, and O. Ruchayskiy, Phenomenology of GeV-scale Heavy Neu- tral Leptons, JHEP11, 032, arXiv:1805.08567 [hep-ph]

    Pith/arXiv arXiv

  67. [67]

    Ballett, T

    P. Ballett, T. Boschi, and S. Pascoli, Heavy Neutral Lep- tons from low-scale seesaws at the DUNE Near Detector, JHEP03, 111, arXiv:1905.00284 [hep-ph]

    Pith/arXiv arXiv 1905

  68. [68]

    Coloma, E

    P. Coloma, E. Fern´ andez-Mart ´ ınez, M. Gonz´ alez-L´ opez, J. Hern´ andez-Garc ´ ıa, and Z. Pavlovic, GeV-scale neutri- nos: interactions with mesons and DUNE sensitivity, Eur. Phys. J. C81, 78 (2021), arXiv:2007.03701 [hep-ph]. 8

    Pith/arXiv arXiv 2021

  69. [69]

    Orloff, A

    J. Orloff, A. N. Rozanov, and C. Santoni, Limits on the mixing of tau neutrino to heavy neutrinos, Phys. Lett. B 550, 8 (2002), arXiv:hep-ph/0208075

    Pith/arXiv arXiv 2002

  70. [70]

    Boiarska, A

    I. Boiarska, A. Boyarsky, O. Mikulenko, and M. Ovchyn- nikov, Constraints from the CHARM experiment on heavy neutral leptons with tau mixing, Phys. Rev. D104, 095019 (2021), arXiv:2107.14685 [hep-ph]

    Pith/arXiv arXiv 2021

  71. [71]

    A. M. Cooper-Sarkaret al.(W A66), Search for Heavy Neutrino Decays in the BEBC Beam Dump Experiment, Phys. Lett. B160, 207 (1985)

    1985

  72. [72]

    Barouki, G

    R. Barouki, G. Marocco, and S. Sarkar, Blast from the past II: Constraints on heavy neutral leptons from the BEBC W A66 beam dump experiment, SciPost Phys.13, 118 (2022), arXiv:2208.00416 [hep-ph]

    Pith/arXiv arXiv 2022

  73. [73]

    J. P. Leeset al.(BaBar), Search for heavy neutral leptons using tau lepton decays at BaBaR, Phys. Rev. D107, 052009 (2023), arXiv:2207.09575 [hep-ex]

    Pith/arXiv arXiv 2023

  74. [74]

    Acciarriet al.(ArgoNeuT), New Constraints on Tau-Coupled Heavy Neutral Leptons with Masses mN=280–970 MeV, Phys

    R. Acciarriet al.(ArgoNeuT), New Constraints on Tau-Coupled Heavy Neutral Leptons with Masses mN=280–970 MeV, Phys. Rev. Lett.127, 121801 (2021), arXiv:2106.13684 [hep-ex]

    Pith/arXiv arXiv 2021

  75. [75]

    Abreuet al.(DELPHI), Search for neutral heavy lep- tons produced in Z decays, Z

    P. Abreuet al.(DELPHI), Search for neutral heavy lep- tons produced in Z decays, Z. Phys. C74, 57 (1997), [Erratum: Z.Phys.C 75, 580 (1997)]

    1997

  76. [76]

    G. B. Gelmini, M. Kawasaki, A. Kusenko, K. Murai, and V. Takhistov, Big Bang Nucleosynthesis constraints on sterile neutrino and lepton asymmetry of the Universe, JCAP09, 051, arXiv:2005.06721 [hep-ph]

    Pith/arXiv arXiv 2005

  77. [77]

    Sabti, A

    N. Sabti, A. Magalich, and A. Filimonova, An Extended Analysis of Heavy Neutral Leptons during Big Bang Nu- cleosynthesis, JCAP11, 056, arXiv:2006.07387 [hep-ph]

    Pith/arXiv arXiv 2006

  78. [78]

    Boyarsky, M

    A. Boyarsky, M. Ovchynnikov, O. Ruchayskiy, and V. Syvolap, Improved big bang nucleosynthesis con- straints on heavy neutral leptons, Phys. Rev. D104, 023517 (2021), arXiv:2008.00749 [hep-ph]

    Pith/arXiv arXiv 2021

  79. [79]

    P. S. B. Dev, Q.-f. Wu, and X.-J. Xu, No Hiding in the Dark: Cosmological Bounds on Heavy Neutral Leptons with Dark Decay Channels, Phys. Rev. D113, 063532 (2026), arXiv:2507.12270 [hep-ph]

    arXiv 2026

  80. [80]

    Bolton, Sterile neutrino constraints (2020)

    P. Bolton, Sterile neutrino constraints (2020)

    2020

Showing first 80 references.