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Heavy Pseudo-Dirac Doublet Dark Matter and Non-Thermal Leptogenesis in Light of the LZ Event

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Masahiro Ibe, Jun Miyamoto

High Energy Physics - Phenomenology · Submitted 21 Oct 2026 · 95 references

Pith's verdict: A careful, honest map of whether LZ-motivated heavy doublet dark matter can coexist with non-thermal leptogenesis; the paper's own conclusion is conditional, and the key parameter point is never exhibited.

T0 · AI review

How this review was made: An AI referee (deepseek/deepseek-v4-flash) read the paper on October 22, 2026 and answered a fixed list of questions about it. T0 is the starting level every paper gets. The levels describe how deeply Pith has checked the paper, never the authors.

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arXiv ID2610.29335 (version 1)
Pith ID4LGSE7DX, Pith's permanent record of this paper and its review
CitationJun Miyamoto, Masahiro Ibe. "Heavy Pseudo-Dirac Doublet Dark Matter and Non-Thermal Leptogenesis in Light of the LZ Event." arXiv:2610.29335 (2026). https://pith.science/paper/4LGSE7DX
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The paper

The paper claims

Heavy pseudo-Dirac doublet dark matter can fit the LZ event, but only in a fine-tuned corner of parameter space.

The reading

The paper asks whether one and the same early-universe reheating history can do two jobs: dilute the over-abundant dark matter of a heavy pseudo-Dirac electroweak doublet (masses $10^2$--$10^4$ TeV, the range that fits the LZ nuclear-recoil candidate) and generate the observed baryon asymmetry through non-thermal leptogenesis. It finds that the reheating temperature needed to hit the observed dark matter abundance is about a TeV, far too low for standard leptogenesis, and that the required CP asymmetry overshoots the Davidson-Ibarra bound by factors of $10^3$--$10^4$. It then shows that dark matter is unavoidably produced after freeze-out, both through virtual electroweak-boson emission in right-handed-neutrino decays and through the thermalization cascade of decay products, and that both channels overproduce dark matter unless pair emission is kinematically forbidden ($M_N < 2m_D$) and the cascade is suppressed by a low reheating temperature and a low inflaton mass. The bottom line is a narrow, fine-tuned window: the scenario can work, but the large CP asymmetry it needs typically requires heavy cancellations in the seesaw mechanism or near-degenerate right-handed neutrinos, and the paper leaves the existence of a point satisfying every condition to a more detailed analysis.

What carries the argument

The load-bearing machinery is a small coupled system of Boltzmann equations (Eqs. (12), (14)--(16)) tracking the inflaton energy density, the radiation bath, the doublet number density, and the $B-L$ asymmetry through inflaton domination and reheating. From it the paper derives the scaling relation for the required reheating temperature, $T_R^{(\mathrm{th})} \simeq 1.3\times10^4\,{\rm GeV}\,(m_D/10^2\,{\rm TeV})^{1/3} x_F^{-4/3}$, and the yield estimate $Y_{B-L} \sim \epsilon T_R/m_\Phi$ that ties baryogenesis to the reheating temperature; the Davidson-Ibarra bound $\epsilon_{\rm DI} \simeq (3/16\pi)(M_{N1}/v^2)m_{\nu 3}$ fixes the reference scale for the required CP enhancement. The two non-thermal production estimates carry the overproduction constraints: the soft-emission branching fraction ${\rm Br}_D \sim (g'^4+3g^4)/(12\times192\pi^4)\,\log^3(M_N^2/m_D^2)$ for gauge-boson-mediated four-body decays, and the cascade yield $m_D Y_D^{(\mathrm{cas})} \sim T_R^5/(m_D^2 T_{\rm end}^2)$ with $T_{\rm end} = \max(T_R,\, 4m_D^2/m_\Phi)$, each capped by a re-annihilation floor. Together these reduce the compatibility question to three simultaneous conditions - $M_N < 2m_D$, low $T_R$ with low enough $m_\Phi$, and $\epsilon$ large enough for the observed $Y_B$ - summarized in Eqs. (85) and (86).

Extended reading notes

Core claim

The paper's central claim is conditional: a heavy pseudo-Dirac electroweak doublet - a pair of vector-like fermions whose two neutral states are split by a few hundred keV and therefore scatter inelastically off nuclei - can serve as dark matter in the $10^2$--$10^4$ TeV range, and the same reheating history that dilutes its thermal relic can also generate the baryon asymmetry, but only in a narrow corner of parameter space. Freeze-out during an inflaton-dominated era followed by entropy production reproduces the observed abundance $\Omega_{\rm DM} h^2 \simeq 0.12$ with reheating temperatures $T_R$ of order a TeV (Eq. (46)). At such low temperatures, non-thermal leptogenesis needs an effective CP asymmetry $\epsilon$ exceeding the Davidson-Ibarra bound by $10^3$--$10^4$ (Eq. (55)), a level the paper exhibits in $N_2$-dominated benchmark points that keep all Yukawa couplings perturbative while demanding cancellations of order $10^3$--$10^4$ among the seesaw contributions. The paper then shows that two post-freeze-out production channels - four-body decays $\bar N_R \to \ell + H + \chi + \bar\chi$ with a branching fraction of order $10^{-4}$, and thermalization-cascade pair production - each overproduce dark matter, so viability requires $M_N < 2m_D$ and a low inflaton mass $m_\Phi \sim 10^6$ GeV at $T_R \sim 0.1$ TeV (Eqs. (85)--(86)). The conclusion is existence in principle, not a demonstrated benchmark: the paper states that whether all requirements can be met simultaneously calls for a more detailed analysis.

Load-bearing premise

Everything rests on the existence of a single parameter set that simultaneously forbids dark matter pair emission in right-handed-neutrino decays ($M_N < 2m_D$), keeps the thermalization cascade small ($T_R \sim 0.1$ TeV and $m_\Phi \sim 10^6$ GeV), and still delivers a CP asymmetry large enough for the observed baryon asymmetry, while the paper's own $N_2$ benchmarks for that large asymmetry use $M_{N2} = 5\times10^9$ GeV, far above $2m_D$, and the paper states that whether these requirements can be satisfied simultaneously calls for a more detailed analysis.

Editorial extensions

If this is right

  • Standard thermal freeze-out is excluded for $m_D \sim 10^2$--$10^4$ TeV, but the observed abundance can be reproduced with $T_R$ of order a TeV via entropy production after freeze-out during inflaton domination.
  • Conventional $N_1$-dominated non-thermal leptogenesis cannot supply the baryon asymmetry in this history: the required $\epsilon$ exceeds the Davidson-Ibarra bound by $10^3$--$10^4$.
  • Whenever $M_N > 2m_D$, the irreducible four-body decay channel alone overproduces dark matter, and varying the inflaton mass cannot cure it because suppressing the four-body channel enhances cascade production.
  • A viable reconciliation requires $M_N < 2m_D$, $T_R \sim 0.1$ TeV, and $m_\Phi \sim 10^6$--$10^7$ GeV (Eq. (85)), together with $\epsilon \sim 10^{-6}$--$10^{-5}$ (Eq. (86)); achieving such $\epsilon$ typically means tuned seesaw cancellations or near-degenerate right-handed neutrinos.
  • Resonant leptogenesis with $\epsilon \sim O(1)$ remains a workable route when $M_N < 2m_D$, and it separates the right-handed-neutrino scale from the inflaton mass.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • The paper's own $N_2$ benchmark points use $M_{N2} = 5\times10^9$ GeV, far above $2m_D$ for the entire $10^2$--$10^4$ TeV dark matter range, so the demonstration of a large CP asymmetry and the suppression of pair emission live in disjoint parameter regions; a full scan that refits the Yukawa couplings with radiative corrections would decide whether any single point satisfies all constraints.
  • The triple-log branching fraction (Eq. (164)) grows toward threshold, so the requirement $M_N < 2m_D$ is effectively a cliff: right-handed neutrinos just above $2m_D$, the region most attractive for the CP asymmetry, give the largest irreducible dark matter yield.
  • The same cascade machinery applies to any thermal-relic dark matter heavier than the reheating temperature, so the constraint pattern - soft-gauge-boson pair emission plus cascade production - should generalize beyond the pseudo-Dirac doublet to other electroweakly charged candidates.
  • Because the paper's estimates are order-of-magnitude and neglect dark matter production before the thermal bath is established, the quantitative boundaries of the allowed window could shift with a more complete calculation, but the qualitative trade-off between the two non-thermal channels would remain.
Original abstract

Motivated by the recent LZ candidate nuclear-recoil event, we study pseudo-Dirac electroweak doublet dark matter in the mass range $10^2$--$10^4\,\mathrm{TeV}$, where bounds from searches for neutrinos produced by dark matter annihilation in the Sun can be evaded. To suppress the excessive thermal relic abundance, we consider freeze-out during inflaton domination followed by entropy production during reheating. We examine whether this cosmological history can also accommodate non-thermal leptogenesis. Our analysis includes dark matter production through the emission of virtual electroweak gauge bosons in right-handed-neutrino decays and through thermalization cascades. Our estimates suggest that the two scenarios can be reconciled if dark matter pair emission in right-handed-neutrino decays is kinematically forbidden and cascade production is sufficiently suppressed. Such a realization, however, requires enhanced CP violation, typically involving fine-tuning in the seesaw mechanism or the right-handed-neutrino mass spectrum.

The compiled record

The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

Compiled by classifier-1.13.0 via TypeSafe API, question bank abstract-p1-20260923, 2026-10-22: 1 request, 5,071 input tokens.

What the abstract itself states, as probabilities: claims first 0.03 · states limitation 0.91 · human participants 0.01 · controlled comparison 0.03 · randomized assignment 0.01 · states quantitative result 0.52 · compares with prior results 0.16 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; .

Motivated by the recent LZ candidate nuclear-recoil event, we study pseudo-Dirac electroweak doublet dark matter in the mass range $10^2$--$10^4\,\mathrm{TeV}$, where bounds from searches for neutrinos produced by dark matter annihilation in the Sun can be evaded. To suppress the excessive thermal relic abundance, we consider freeze-out during inflaton domination followed by entropy production during reheating. We examine whether this cosmological history can also accommodate non-thermal leptogenesis. Our analysis includes dark matter production through the emission of virtual electroweak gauge bosons in right-handed-neutrino decays and through thermalization cascades. Our estimates suggest that the two scenarios can be reconciled if dark matter pair emission in right-handed-neutrino decays is kinematically forbidden and cascade production is sufficiently suppressed. Such a realization, however, requires enhanced CP violation, typically involving fine-tuning in the seesaw mechanism or the right-handed-neutrino mass spectrum.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 Motivated by the recent LZ candidate nuclear-recoil event, we study pseudo-Dirac electroweak doublet dark matter in the mass range $10^2$--$10^4\,\mathrm{TeV}$, where bounds from searches for neutrinos produced by dark matter annihilation in the Sun can be evaded. contribution 0.87 0.53 0.07 asserted 0.84
s1 To suppress the excessive thermal relic abundance, we consider freeze-out during inflaton domination followed by entropy production during reheating. method 0.86 0.50 0.04 asserted 0.89
s2 We examine whether this cosmological history can also accommodate non-thermal leptogenesis. contribution 0.97 0.58 0.04 hedged possibility 0.50
s3 Our analysis includes dark matter production through the emission of virtual electroweak gauge bosons in right-handed-neutrino decays and through thermalization cascades. method 0.74 0.72 0.04 asserted 0.99
s4 Our estimates suggest that the two scenarios can be reconciled if dark matter pair emission in right-handed-neutrino decays is kinematically forbidden and cascade production is sufficiently suppressed. result 0.94 0.87 0.58 hedged possibility 0.99
s5 Such a realization, however, requires enhanced CP violation, typically involving fine-tuning in the seesaw mechanism or the right-handed-neutrino mass spectrum. limitation 0.60 0.62 0.28 asserted 0.84

What kind of paper the classifier reports this is: theoretical result 1.00 · evidence from argument 0.45.

What was examined, and what was not

sources read
  • arXiv listing abstract v1
not examined
  • full text
  • figures and tables
  • references and citing sentences
  • relations to other papers
levels run
  • P abstract
not run
  • S sections
  • T body sentences
  • C citations
  • R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

Figures
Figure 1. Schematic evolution of the inflaton and radiation energy densities during and after inflation.
Figure 2. Reheating temperature T (th) R required for thermal production to reproduce the observed dark matter abundance, shown as a function of mD for fixed values of T (init) max /mD. The gray region does not satisfy the approximate chemical-equilibrium criterion in Eq. (51), which assumes T∗ < Tmax. The right vertical axis gives a reference conversion from TR to Tmax for mΦ = 1010 GeV in Eq. (27)
Figure 3. Effective CP asymmetry required to reproduce the observed baryon abundance, normalized () ()
Figure 4. Branching fraction for the four-body decay
Figure 5. Non-thermal dark matter abundance as a function of the inflaton mass
Figure 6. Non-thermal dark matter abundance as a function of the inflaton mass
Figure 7. The effective power-law exponent d ln T (th) R /d ln mD along a contour of fixed relic abun￾dance, shown as a function of xF = mD/TF . up to a numerical factor of order unity, where HF ≡ H(xF ) and ⟨σeffv⟩F ≡ ⟨σeffv⟩(xF ). For ⟨σeffv⟩ ∝ m−2 D , the freeze-out condition implies  xF − 13 2  x −5/2 F e xF ∝ T 2 Rm−3 D , (122) where we have used HF = HR(xR/xF ) 4 , HR ∝ T 2 R, and xR = mD/TR. On the other hand, for a given xF , the dark matter abundance mDYD is given in Eq. (44). Thus, by requiring that the predicted reproduces the observed dark matter abudnance, we fi

Figures reproduced from arXiv:2610.29335 by the authors.

References

Discussion

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