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REVIEW 3 major objections 5 minor 47 references

Future Z factories such as CEPC and FCC-ee could reveal the neutrino mass ordering through the flavor structure of heavy neutral lepton decays—probing total mixings down to about 4×10⁻⁹ and distinguishing the two hierarchies above about 10⁻

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 →

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2026-08-03 10:20 UTC pith:2MF5XKZK

load-bearing objection Worth a serious look, but the headline reach numbers are built on a parameter-space area the model does not actually allow at fixed U_tot^2. the 3 major comments →

arxiv 2601.10311 v2 pith:2MF5XKZK submitted 2026-01-15 hep-ph

Revealing Neutrino Mass Ordering at CEPC and FCC-ee

Wei Liu , Supriya Senapati , Jin Sun This is my paper
classification hep-ph
keywords heavy neutral leptonsneutrino mass orderingType-I seesawlepton flavorCEPCFCC-eeZ factoryCasas-Ibarra parametrization
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 the long-standing question of whether neutrinos are ordered normally or inverted can be answered at high-energy lepton colliders, not just in oscillation experiments. In the minimal Type-I seesaw with two nearly degenerate heavy neutral leptons, the relative couplings of the heavy states to electron, muon, and tau flavors are fixed by the light-neutrino mass spectrum: normal ordering strongly suppresses the electron coupling, while inverted ordering gives roughly democratic couplings. The authors show that at the Z pole of CEPC or FCC-ee, counting electron vs muon final states in prompt HNL decays provides a statistically powerful discrimination, sensitive to total mixings U_tot^2 ≳ 4×10⁻⁹ and able to tell the orderings apart for U_tot^2 ≳ 10⁻⁶. If correct, this would make colliders a complementary, ultraviolet probe of the same property that low-energy oscillation experiments pursue, and a direct test of the minimal two-HNL seesaw.

Core claim

The central claim is that the flavor composition of HNL interactions is not arbitrary but is dictated by the light-neutrino mass ordering. In the two-HNL minimal seesaw, the Casas–Ibarra parametrization yields U^2_alphaN/U^2_tot as a function of the PMNS matrix and light neutrino masses, so the predicted ranges for NH and IH are distinct: NH gives U^2_eN/U^2_tot in (3.1e-3,0.14) with muon and tau fractions up to ~0.88, while IH allows electron fractions from 0.021 to 0.96. At a Z factory with 200 ab^-1, single-HNL production followed by decay into a charged lepton plus two jets provides enough events to exclude the wrong ordering at roughly 2 sigma for the quoted mixings; the fraction of the

What carries the argument

The key object is Eq. (1), the seesaw relation between the measurable HNL mixing U^2_alphaN, the total mixing U^2_tot, and the light-neutrino parameters: through the Casas–Ibarra complex orthogonal matrix (parametrized by complex omega, with x_omega = e^{Im omega}), both the overall size and the flavor ratios of the heavy–light mixing are fixed. This identity converts the neutrino mass ordering—a low-energy property—into a high-energy prediction for the relative event rates in the electron and muon channels. The analysis then uses a chi-squared comparison of observed flavor fractions against the predicted NH/IH regions, quantified by the overlap fraction K, to estimate the discrimination pow

Load-bearing premise

The analysis assumes that, for a fixed total mixing U_tot^2, the HNL flavor ratios can range over the full predicted NH/IH regions, even though in the seesaw model U_tot^2 and the flavor ratios are controlled by the same parameter (x_omega), so a fixed U_tot^2 leaves only a restricted one-dimensional set of allowed flavor ratios; using the full ranges can overstate the discrimination power.

What would settle it

Recompute the K fraction for a given m_N and U_tot^2 (e.g., 50 GeV and 10^-7) by scanning the seesaw parameters (Im omega, PMNS phases) subject to the exact constraint that U_tot^2 takes the fixed value, producing the true admissible (R_e,R_mu) points; if these restricted points make NH and IH overlap substantially, the advertised thresholds fail, whereas if they largely separate, the claim holds.

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

If this is right

  • If the predictions of Eq. (1) hold, CEPC/FCC-ee can probe mass-ordering-sensitive parameter space at U_tot^2 ≃ 4×10⁻⁹ and achieve near-maximal discrimination, K ≃ 90%, for U_tot^2 ≳ 10⁻⁶—about an order of magnitude below current experimental bounds.
  • The IH flavor region is relatively stable under improved oscillation measurements, so the method is robust; by contrast, shrinking the allowed Dirac CP phase narrows the NH region and sharpens the discrimination.
  • A consistent mass-ordering determination from colliders and from low-energy oscillation experiments would corroborate the minimal two-HNL seesaw; any mismatch would point to dynamics beyond it.
  • The irreducible diboson background of ~1.4×10⁵ events per flavor sets a floor: for N0 smaller than about twice the square root of the background, the overlap region covers the whole parameter space and K vanishes.

Where Pith is reading between the lines

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

  • The paper evaluates the predicted regions as full two-dimensional areas, but for fixed m_N and U_tot^2 the seesaw model restricts (R_e,R_mu) to a one-dimensional curve because x_omega controls both quantities; recomputing K with this restriction could move the quoted thresholds upward.
  • The same flavor-ratio observable contains information about the Dirac CP phase and the lightest neutrino mass, so a future measurement would do more than fix the ordering—it could constrain the full seesaw parameter set.
  • Including tau final states (with improved tau tagging) or displaced-vertex searches at other facilities could extend the method to smaller mixings or heavier masses, where prompt Z-factory decays are kinematically suppressed.
  • If a signal appears, the ratio R_e/R_mu alone—independent of the total production rate—could distinguish the orderings, making the conclusion robust to uncertainties in luminosity and cross-section normalization.

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

3 major / 5 minor

Summary. The Letter proposes that in the minimal Type-I seesaw with two quasi-degenerate HNLs, the heavy-light mixing flavor ratios R_α=U_αN^2/U_tot^2 are fixed by the light-neutrino mass spectrum and the PMNS matrix (Eq. 1). Using NuFIT/JUNO oscillation ranges, it defines NH and IH regions in the (R_e,R_μ) plane, estimates event rates for e+e−→Nν, N→ℓjj at CEPC/FCC-ee with L=200 ab^-1, and introduces a fraction K (Eq. 7) for which the mass ordering can be unambiguously identified. The paper claims thresholds U_tot^2≳4×10^-9 and ≳10^-6 for probing and discriminating the ordering at m_N≈50 GeV.

Significance. The idea is creative and timely: collider flavor ratios could provide a genuinely complementary mass-ordering probe, and the Casas-Ibarra derivation is transparent and parameter-free in the sense that no collider observable is fitted to the model. The paper uses up-to-date oscillation inputs (NuFIT 6.0 and JUNO) and makes a concrete experimental projection. The qualitative pattern — suppressed U_eN in NH and a more democratic flavor pattern in IH — is physically well motivated. However, the advertised numeric reach rests on a parameter-space identification that, as written, overcounts the accessible model points. The central quantitative claims are therefore not yet supported, although they are likely reparable with a recomputation over the actual seesaw parameters.

major comments (3)
  1. [Eq. (1), 'Sensitivity on neutrino mass ordering', Figs. 2–3] The theory regions used in the sensitivity analysis are not the physically accessible sets at fixed U_tot^2. Eq. (1) gives U_tot^2 = (m2+m3)/(2 m_N)(x_ω^2 + x_ω^{-2}) for NH (and analogously for IH). Thus once m_N and U_tot^2 are fixed, x_ω is determined up to x_ω → 1/x_ω. For each PMNS point the reachable (R_e,R_μ) values form a curve/finite set, not the full 2D regions shaded in Fig. 2 or implied by Table I. Since N0 in Eq. (4) depends on U_tot^2, one cannot simultaneously fix U_tot^2 and marginalize over x_ω when defining the predicted NH/IH regions. The K contours and the abstract thresholds built on Eq. (7) are therefore not well defined. A recomputation scanning the actual Casas-Ibarra parameters (PMNS entries, masses, x_ω) with the U_tot^2 constraint imposed is required.
  2. [Eq. (7) and Fig. 3] K is defined as 1 − S_NH∩IH/S_tot, an area ratio in the (R_e,R_μ) plane, but it is interpreted as 'the fraction of the allowed seesaw parameter space' in the Fig. 3 caption. The map from (PMNS, x_ω) to R is many-to-one and not area-preserving; equal areas in R-space do not correspond to equal fractions of the model parameter space. Even if the full triangles were valid, Eq. (7) would not be a parameter-space fraction. A proper definition should integrate over the model parameters with a specified measure (for example uniform in log10 U_tot^2 and over x_ω/PMNS) or should report the reach as a function of the true model point.
  3. [Eq. (6) and Table II] The test-statistic construction is underspecified at a point that affects the conclusions. The text refers to 'min(χ2_NH/IH)' but does not state whether the minimum is taken over the predicted NH/IH region, over x_ω, or over the PMNS parameters; importantly, the minimization must be over the x_ω values consistent with the fixed U_tot^2. As written, the favored/excluded regions in Fig. 2 are not reproducible, and the statement that min χ2>4 corresponds to 'approximately 2σ' is not a standard confidence-level construction. Please specify the exact minimization and use a conventional statistical procedure or Monte Carlo p-value.
minor comments (5)
  1. [Eq. (1)] x_ω and the PMNS convention (including Majorana phases) are defined only in Appendix A; the main text should define them so Eq. (1) is self-contained.
  2. [Table I / Fig. 1] The scan ranges are not fully specified. Please state the ranges for x_ω (Re ω and Im ω), the lightest neutrino mass, and Majorana phases; otherwise the Table I ranges cannot be reproduced.
  3. [Eq. (4)] The prefactor N0 ~ O(10^11) U_tot^2 is asserted without derivation. Provide the explicit formula for Br(Z→Nν) and the numerical inputs (Z-pole cross section, luminosity, acceptance) so the sensitivity estimate is reproducible.
  4. [Fig. 3 caption] The phrase 'fraction of parameter space (in log10 scale)' is unclear because Eq. (7) is a simple area ratio in (R_e,R_μ); either define a logarithmic measure or remove the phrase.
  5. [Fig. 1] The dashed red/brown curves corresponding to T2K/NOvA best-fit δ_D are not described in the caption; please state the specific δ_D values and uncertainty assumptions in the caption.

Circularity Check

0 steps flagged

No significant circularity: the central flavor prediction is derived from the Casas-Ibarra parametrization and external neutrino oscillation data, not from a fitted or self-referential input.

full rationale

The paper's central derivation chain is self-contained: Eq. (1), obtained within the minimal two-HNL Type-I seesaw and attributed to the external reference [36], expresses U_alphaN^2 and U_tot^2 in terms of the light-neutrino masses, the PMNS matrix, and the Casas-Ibarra parameter x_omega. The predicted NH/IH flavor regions in Fig. 1 and Table I are obtained by scanning external NuFIT 6.0 and JUNO results, with the standard Casas-Ibarra parametrization [56]. No parameter is fitted to the collider 'prediction'; the sensitivity maps in Figs. 2-3 are projections of this model onto the (R_e,R_mu) plane. The many self-citations in the HNL bibliography (refs. [14-33]) support only the background claim that existing searches are mostly single-flavor and mass-ordering insensitive; they are not load-bearing for the flavor-ordering relation, which rests on external references [34-36,56]. A methodological caveat exists: K in Eq. (7) is an area ratio in the (R_e,R_mu) plane, while Fig. 3 labels it a fraction of the seesaw parameter space, and Eq. (1) restricts the reachable R points at fixed U_tot^2. This is a validity/interpretation issue for the sensitivity contours, but it is not circularity: K is not an input quantity being renamed as a prediction, and the flavor prediction itself does not reduce to its inputs by construction.

Axiom & Free-Parameter Ledger

4 free parameters · 7 axioms · 0 invented entities

The paper introduces no new entities: HNLs are the standard Type-I seesaw particles. The main model overhead is the minimal two-HNL pseudo-Dirac framework, the free seesaw parameter x_omega, and the unstated cancellation that allows large mixing without large light neutrino masses. The event-rate constant N0 is also not derived. Most other inputs are external oscillation data and standard formulas.

free parameters (4)
  • x_omega = exp(Im omega)
    Appears explicitly in Eq. (1) and controls the HNL flavor ratios over the ranges in Table I. The paper's scan description mentions only neutrino oscillation parameters, so the treatment of x_omega is ambiguous; for fixed m_N and U_tot^2 it is determined by Eq. (1).
  • HNL mass m_N
    Scanned over the (m_N, U_tot^2) plane in Fig. 3; sensitivity and kinematical suppression depend on it. It is a model parameter, not fitted to data by the paper.
  • Total mixing U_tot^2
    Scanned input; sets the event rate N0 in Eq. (4) and determines the reach thresholds. It is the parameter the future experiment would measure.
  • N0 prefactor in Eq. (4) = O(10^11)
    The event-rate constant NS,alpha ≈ O(10^11) U_tot^2 R_alpha is stated without derivation. The advertised U_tot^2 thresholds scale directly with this hand-set constant.
axioms (7)
  • domain assumption Minimal two-HNL Type-I seesaw with one massless light neutrino (m1=0 for NH, m3=0 for IH).
    The entire flavor-ordering correlation is derived under this assumption; it is not tested against three-HNL or non-minimal variants.
  • domain assumption Pseudo-Dirac condition: M1 ≃ M2 and Theta_l1 = ± i Theta_l2.
    Stated in Appendix A. This condition allows large U_tot^2 while keeping light neutrino masses small, but the paper nevertheless quotes the naive seesaw bound sum m_nu ≈ U_tot^2 m_N in Fig. 3 without explaining the cancellation.
  • standard math Casas-Ibarra parametrization with the R_NH and R_IH matrices of Eq. (A5).
    A standard exact parametrization of the seesaw; the paper relies on it for Eq. (1).
  • domain assumption Decay-length formula Eq. (A7) and the prompt condition L_N < 1 mm.
    Taken from Ref. [57]; determines which regions of (m_N, U_tot^2) contribute prompt decays and therefore enter the sensitivity calculation.
  • domain assumption Background is only irreducible four-fermion eνjj / muνjj at 0.72 fb per flavor, with no detector-level corrections.
    Appendix B; used to set N_B = 1.4×10^5 in Eq. (5). Other SM backgrounds are argued to be negligible without a full simulation.
  • domain assumption The chi-squared in Eq. (6) with min(chi^2) > 4 defines the 2-sigma discriminating regions; no systematic uncertainties are included.
    The K contours in Fig. 3 are built on this statistical model.
  • domain assumption Oscillation parameter ranges from NuFIT 6.0 and JUNO first results.
    External inputs used to generate the predicted NH and IH regions; they are not derived in this paper.

pith-pipeline@v1.3.0-alltime-deepseek · 10266 in / 24798 out tokens · 276424 ms · 2026-08-03T10:20:55.958284+00:00 · methodology

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read the original abstract

The neutrino masses ordering remains one of the most important open questions in neutrino physics. While upcoming oscillation experiments aim to resolve this problem at low energies, complementary approaches are highly desirable. In this Letter, we show that the neutrino mass ordering can be probed at high-energy colliders through the lepton-flavor structure of heavy neutral lepton (HNL) interactions. In the minimal Type-I seesaw scenario with two nearly degenerate HNLs, the heavy--light neutrino mixings are strongly correlated with the light-neutrino mass spectrum, leading to distinct flavor patterns for the normal and inverted hierarchies. We demonstrate that future $Z$ factories, such as CEPC and FCC-ee, can probe the neutrino mass ordering for total HNL mixings as small as $U_{\rm tot}^2 \gtrsim 4 \times 10^{-9}$, and discriminate between the two hierarchies for $U_{\rm tot}^2 \gtrsim 10^{-6}$. Our results establish collider searches for HNLs as a powerful and complementary probe of the neutrino mass ordering.

Figures

Figures reproduced from arXiv: 2601.10311 by Jin Sun, Supriya Senapati, Wei Liu.

Figure 1
Figure 1. Figure 1: FIG. 1. Ternary plot showing the distribution of flavor [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Sensitivity of the neutrino mass orderings in the plane of ( [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Fraction of the parameter space (in log [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗

discussion (0)

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Reference graph

Works this paper leans on

47 extracted references · 41 linked inside Pith

  1. [5]

    Minkowski,µ→eγat a Rate of One Out of10 9 Muon Decays?, Phys

    P. Minkowski,µ→eγat a Rate of One Out of10 9 Muon Decays?, Phys. Lett. B67(1977) 421–428

    1977

  2. [6]

    Yanagida,Horizontal Symmetry and Masses of Neutrinos, Prog

    T. Yanagida,Horizontal Symmetry and Masses of Neutrinos, Prog. Theor. Phys.64(1980) 1103

    1980

  3. [7]

    Gell-Mann, P

    M. Gell-Mann, P. Ramond, and R. Slansky,Complex Spinors and Unified Theories, Conf. Proc. C790927 (1979) 315–321, [arXiv:1306.4669]

    Pith/arXiv arXiv 1979

  4. [8]

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

    1980

  5. [9]

    Kaneta, Z

    K. Kaneta, Z. Kang, and H.-S. Lee,Right-handed neutrino dark matter under theB−Lgauge interaction, JHEP02(2017) 031, [arXiv:1606.09317]

    Pith/arXiv arXiv 2017

  6. [10]

    Bondarenko, A

    K. Bondarenko, A. Boyarsky, D. Gorbunov, and O. Ruchayskiy,Phenomenology of GeV-scale Heavy Neutral Leptons, JHEP11(2018) 032, [arXiv:1805.08567]

    Pith/arXiv arXiv 2018

  7. [11]

    D. A. Bryman and R. Shrock,Constraints on Sterile Neutrinos in the MeV to GeV Mass Range, Phys. Rev. D100(2019) 073011, [arXiv:1909.11198]

    Pith/arXiv arXiv 2019

  8. [12]

    Balaji, M

    S. Balaji, M. Ramirez-Quezada, and Y.-L. Zhou,CP violation and circular polarisation in neutrino radiative decay, JHEP04(2020) 178, [arXiv:1910.08558]

    Pith/arXiv arXiv 2020

  9. [13]

    P. D. Bolton, F. F. Deppisch, and P. S. Bhupal Dev, Neutrinoless double beta decay versus other probes of heavy sterile neutrinos, JHEP03(2020) 170, [arXiv:1912.03058]

    Pith/arXiv arXiv 2020

  10. [14]

    Liu, K.-P

    W. Liu, K.-P. Xie, and Z. Yi,Testing leptogenesis at the LHC and future muon colliders: AZ ′ scenario, Phys. Rev. D105(2022), no. 9 095034, [arXiv:2109.15087]

    Pith/arXiv arXiv 2022

  11. [15]

    A. M. Abdullahi et al.,The present and future status of heavy neutral leptons, J. Phys. G50(2023), no. 2 020501, [arXiv:2203.08039]

    Pith/arXiv arXiv 2023

  12. [16]

    Zhang and W

    Y. Zhang and W. Liu,Probing active-sterile neutrino transition magnetic moments at LEP and CEPC, Phys. Rev. D107(2023), no. 9 095031, [arXiv:2301.06050]

    Pith/arXiv arXiv 2023

  13. [17]

    Barducci, W

    D. Barducci, W. Liu, A. Titov, Z. S. Wang, and Y. Zhang,Probing the dipole portal to heavy neutral leptons via meson decays at the high-luminosity LHC, Phys. Rev. D108(2023), no. 11 115009, [arXiv:2308.16608]

    Pith/arXiv arXiv 2023

  14. [18]

    W. Liu, F. F. Deppisch, and Z. Chen,Testing leptogenesis and seesaw in the B-L model using long-lived particle searches, Phys. Rev. D110(2024), no. 3 035017, [arXiv:2312.11165]

    Pith/arXiv arXiv 2024

  15. [19]

    W. Liu, S. Kulkarni, and F. F. Deppisch,Heavy neutrinos at the FCC-hh in the U(1)B-L model, Phys. Rev. D105(2022), no. 9 095043, [arXiv:2202.07310]

    Pith/arXiv arXiv 2022

  16. [20]

    C. Han, T. Li, and C.-Y. Yao,Searching for heavy neutrino in terms of tau lepton at future hadron collider, Phys. Rev. D104(2021), no. 1 015036, [arXiv:2103.03548]

    Pith/arXiv arXiv 2021

  17. [21]

    Das and N

    A. Das and N. Okada,Bounds on heavy Majorana neutrinos in type-I seesaw and implications for collider searches, Phys. Lett. B774(2017) 32–40, [arXiv:1702.04668]

    Pith/arXiv arXiv 2017

  18. [22]

    Maiezza, M

    A. Maiezza, M. Nemevˇ sek, and F. Nesti,Lepton Number Violation in Higgs Decay at LHC, Phys. Rev. Lett.115(2015) 081802, [arXiv:1503.06834]

    Pith/arXiv arXiv 2015

  19. [23]

    F. F. Deppisch, W. Liu, and M. Mitra,Long-lived Heavy Neutrinos from Higgs Decays, JHEP08(2018) 181, [arXiv:1804.04075]. 7

    Pith/arXiv arXiv 2018

  20. [24]

    J. D. Mason,Time-Delayed Electrons from Higgs Decays to Right-Handed Neutrinos, JHEP07(2019) 089, [arXiv:1905.07772]

    Pith/arXiv arXiv 2019

  21. [25]

    Accomando, L

    E. Accomando, L. Delle Rose, S. Moretti, E. Olaiya, and C. H. Shepherd-Themistocleous,Novel SM-like Higgs decay into displaced heavy neutrino pairs in U(1)’ models, JHEP04(2017) 081, [arXiv:1612.05977]

    Pith/arXiv arXiv 2017

  22. [26]

    A. M. Gago, P. Hern´ andez, J. Jones-P´ erez, M. Losada, and A. Moreno Brice˜ no,Probing the Type I Seesaw Mechanism with Displaced Vertices at the LHC, Eur. Phys. J. C75(2015), no. 10 470, [arXiv:1505.05880]

    Pith/arXiv arXiv 2015

  23. [27]

    Jones-P´ erez, J

    J. Jones-P´ erez, J. Masias, and J. D. Ruiz-´Alvarez, Search for Long-Lived Heavy Neutrinos at the LHC with a VBF Trigger, Eur. Phys. J. C80(2020), no. 7 642, [arXiv:1912.08206]

    Pith/arXiv arXiv 2020

  24. [28]

    W. Liu, J. Li, J. Li, and H. Sun,Testing the seesaw mechanisms via displaced right-handed neutrinos from a light scalar at the HL-LHC, Phys. Rev. D106(2022), no. 1 015019, [arXiv:2204.03819]

    Pith/arXiv arXiv 2022

  25. [29]

    J. Li, W. Liu, and H. Sun,Z’ mediated right-handed neutrinos from meson decays at the F ASER, Phys. Rev. D109(2024), no. 3 035022, [arXiv:2309.05020]

    Pith/arXiv arXiv 2024

  26. [30]

    F. F. Deppisch, S. Kulkarni, and W. Liu,Sterile Neutrinos at MAPP in the B-L Model, 11, 2023. arXiv:2311.01719

    arXiv 2023

  27. [31]

    W. Liu, S. Kulkarni, and F. F. Deppisch,Revealing the origin of neutrino masses through displaced shower searches in the CMS muon system, Phys. Rev. D111 (2025), no. 9 093003, [arXiv:2407.20676]

    Pith/arXiv arXiv 2025

  28. [32]

    Z. S. Wang, Y. Zhang, and W. Liu,Searching for heavy neutral leptons coupled to axion-like particles at the LHC far detectors and SHiP, JHEP01(2025) 070, [arXiv:2409.18424]

    Pith/arXiv arXiv 2025

  29. [33]

    Z. S. Wang, Y. Zhang, and W. Liu,Long-lived sterile neutrinos from an axionlike particle at Belle II, Phys. Rev. D111(2025), no. 3 035010, [arXiv:2410.00491]

    Pith/arXiv arXiv 2025

  30. [34]

    Tastet, O

    J.-L. Tastet, O. Ruchayskiy, and I. Timiryasov, Reinterpreting the ATLAS bounds on heavy neutral leptons in a realistic neutrino oscillation model, JHEP 12(2021) 182, [arXiv:2107.12980]

    Pith/arXiv arXiv 2021

  31. [35]

    Abada, P

    A. Abada, P. Escribano, X. Marcano, and G. Piazza, Collider searches for heavy neutral leptons: beyond simplified scenarios, Eur. Phys. J. C82(2022), no. 11 1030, [arXiv:2208.13882]

    Pith/arXiv arXiv 2022

  32. [36]

    Eijima, M

    S. Eijima, M. Shaposhnikov, and I. Timiryasov, Parameter space of baryogenesis in theνMSM, JHEP 07(2019) 077, [arXiv:1808.10833]

    Pith/arXiv arXiv 2019

  33. [37]

    Esteban, M

    I. Esteban, M. C. Gonzalez-Garcia, M. Maltoni, I. Martinez-Soler, J. P. Pinheiro, and T. Schwetz, NuFit-6.0: updated global analysis of three-flavor neutrino oscillations, JHEP12(2024) 216, [arXiv:2410.05380]

    Pith/arXiv arXiv 2024

  34. [38]

    Esteban, M

    I. Esteban, M. C. Gonzalez-Garcia, M. Maltoni, I. Martinez-Soler, J. P. Pinheiro, and T. Schwetz, NuFIt-6.0 (2024),http://www.nu-fit.org. [39]JUNOCollaboration, A. Abusleme et al.,First measurement of reactor neutrino oscillations at JUNO, arXiv:2511.14593

    arXiv 2024

  35. [40]

    Ge, C.-F

    S.-F. Ge, C.-F. Kong, and P. Pasquini,Improving CP measurement with THEIA and muon decay at rest, Eur. Phys. J. C82(2022), no. 6 572, [arXiv:2202.05038]. [41]T2KCollaboration, K. Abe et al.,Measurements of neutrino oscillation parameters from the T2K experiment using3.6×10 21 protons on target, Eur. Phys. J. C83(2023), no. 9 782, [arXiv:2303.03222]. [42]N...

    Pith/arXiv arXiv 2022

  36. [46]

    T. H. Kwok, L. Li, T. Liu, and A. Rock,Searching for heavy neutral leptons at a future muon collider, Phys. Rev. D110(2024), no. 7 075009, [arXiv:2301.05177]

    Pith/arXiv arXiv 2024

  37. [47]

    P. Li, Z. Liu, and K.-F. Lyu,Heavy neutral leptons at muon colliders, JHEP03(2023) 231, [arXiv:2301.07117]

    Pith/arXiv arXiv 2023

  38. [48]

    Mkeka la, J

    K. Mkeka la, J. Reuter, and A. F. ˙Zarnecki,Optimal search reach for heavy neutral leptons at a muon collider, Phys. Lett. B841(2023) 137945, [arXiv:2301.02602]

    Pith/arXiv arXiv 2023

  39. [49]

    A. Das, J. Li, S. Mandal, T. Nomura, and R. Zhang, Testing tree level TeV scale seesaw scenarios in µTRISTAN, Phys. Rev. D112(2025), no. 3 035008, [arXiv:2410.21956]

    Pith/arXiv arXiv 2025

  40. [50]

    Alwall, R

    J. Alwall, R. Frederix, S. Frixione, V. Hirschi, F. Maltoni, O. Mattelaer, H. S. Shao, T. Stelzer, P. Torrielli, and M. Zaro,The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations, JHEP07(2014) 079, [arXiv:1405.0301]. [51]IDEA Study GroupCollaboration, M. Abbrescia et ...

    Pith/arXiv arXiv 2014

  41. [52]

    Ai et al.,Flavor Physics at the CEPC: a General Perspective, Chin

    X. Ai et al.,Flavor Physics at the CEPC: a General Perspective, Chin. Phys.49(2025), no. 10 103003, [arXiv:2412.19743]

    arXiv 2025

  42. [53]

    Alekhin et al.,A facility to Search for Hidden Particles at the CERN SPS: the SHiP physics case, Rept

    S. Alekhin et al.,A facility to Search for Hidden Particles at the CERN SPS: the SHiP physics case, Rept. Prog. Phys.79(2016), no. 12 124201, [arXiv:1504.04855]

    Pith/arXiv arXiv 2016

  43. [54]

    Drewes and J

    M. Drewes and J. Hajer,Heavy Neutrinos in displaced vertex searches at the LHC and HL-LHC, JHEP02 (2020) 070, [arXiv:1903.06100]. [55]PlanckCollaboration, N. Aghanim et al.,Planck 2018 results. VI. Cosmological parameters, Astron. Astrophys.641(2020) A6, [arXiv:1807.06209]. [Erratum: Astron.Astrophys. 652, C4 (2021)]

    Pith/arXiv arXiv 2020

  44. [56]

    J. A. Casas and A. Ibarra,Oscillating neutrinos and µ→e, γ, Nucl. Phys. B618(2001) 171–204, [hep-ph/0103065]

    Pith/arXiv arXiv 2001

  45. [57]

    Drewes,Distinguishing Dirac and Majorana Heavy Neutrinos at Lepton Colliders, PoSICHEP2022 (2022) 608, [arXiv:2210.17110]

    M. Drewes,Distinguishing Dirac and Majorana Heavy Neutrinos at Lepton Colliders, PoSICHEP2022 (2022) 608, [arXiv:2210.17110]

    Pith/arXiv arXiv 2022

  46. [58]

    Ibarra, E

    A. Ibarra, E. Molinaro, and S. T. Petcov,Low Energy Signatures of the TeV Scale See-Saw Mechanism, Phys. Rev. D84(2011) 013005, [arXiv:1103.6217]. 8

    Pith/arXiv arXiv 2011

  47. [59]

    D. N. Dinh, A. Ibarra, E. Molinaro, and S. T. Petcov, Theµ−eConversion in Nuclei,µ→eγ, µ→3eDecays and TeV Scale See-Saw Scenarios of Neutrino Mass Generation, JHEP08(2012) 125, [arXiv:1205.4671]. [Erratum: JHEP 09, 023 (2013)]. [60]MEG IICollaboration, K. Afanaciev et al.,New limit on theµ + →e +γdecay with the MEG II experiment, Eur. Phys. J. C85(2025), ...

    Pith/arXiv arXiv 2012