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arxiv: 2601.15921 · v2 · submitted 2026-01-22 · ✦ hep-ph

Dominant Thermal Resonant Mechanism for Low-Scale Leptogenesis

Shao-Ping Li , Apostolos Pilaftsis This is my paper

Pith reviewed 2026-05-16 12:19 UTC · model grok-4.3

classification ✦ hep-ph
keywords leptogenesissterile neutrinosbaryon asymmetryHiggs decaysflavour coherencethermal effectslow-scale modelsneutrino mixing
0
0 comments X

The pith

A thermal resonant channel from Higgs decays can generate the observed baryon asymmetry even when sterile neutrinos are not nearly degenerate.

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

The paper demonstrates that a new thermal resonant process, arising from Higgs decays into leptons and relativistic singlet neutrinos, can dominate lepton asymmetry production through thermally generated flavour coherences in the lepton doublets. This Thermal Resonant Leptogenesis (TRL) mechanism operates at low scales and produces the required baryon asymmetry without relying on resonant enhancement from quasi-degenerate sterile neutrino masses. A reader would care because it expands the viable parameter space for low-scale leptogenesis and predicts a distinct pattern of active-sterile neutrino mixing that future experiments can test.

Core claim

The central claim is that thermally induced Higgs decays to lepton doublets and singlet neutrinos, amplified by resonant lepton-doublet flavour coherences, generate a lepton asymmetry that converts to the observed baryon asymmetry via sphaleron processes, even in the absence of quasi-degenerate sterile neutrinos.

What carries the argument

The Thermal Resonant Leptogenesis (TRL) channel, in which thermally generated resonant coherences in lepton doublets enhance the asymmetry from Higgs decays to relativistic singlet neutrinos.

Load-bearing premise

Thermally generated resonant lepton-doublet flavour coherences must be present and able to dominate asymmetry generation when sterile neutrinos are not quasi-degenerate.

What would settle it

A full numerical solution of the Boltzmann equations for the early universe showing that the thermal resonant contribution falls short of the observed baryon asymmetry by more than an order of magnitude when sterile neutrino masses differ by more than a few percent.

Figures

Figures reproduced from arXiv: 2601.15921 by Apostolos Pilaftsis, Shao-Ping Li.

Figure 1
Figure 1. Figure 1: FIG. 1. Tree-level and one-loop Higgs decay to leptons and relativis [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. The parameter space of low-scale leptogenesis from the third channel presented in this Letter. We fix the lightest SM neutrino mass [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
read the original abstract

We explicitly demonstrate the importance of a new thermal resonant channel in the context of low-scale leptogenesis, which goes beyond the well-known mixing and oscillation of massive singlet neutrinos. This new channel is always present when considering the thermally-induced Higgs decay to leptons and relativistic singlet neutrinos, and can become dominant thanks to thermally-generated resonant lepton-doublet flavour coherences. This mechanism, which we call Thermal Resonant Leptogenesis (TRL), can yield the observed baryon asymmetry in our universe, even if there is no resonant enhancement from quasi-degenerate sterile neutrinos. The required active-to-sterile neutrino mixing for TRL differs from other known low-scale leptogenesis scenarios and can be probed in fixed-target and long-lived particle experiments, and by displaced vertex searches at high-energy colliders.

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 / 1 minor

Summary. The manuscript claims to explicitly demonstrate a new thermal resonant leptogenesis (TRL) mechanism arising from thermally-induced Higgs decays to leptons and relativistic singlet neutrinos. This channel generates lepton-doublet flavour coherences that can dominate asymmetry production and yield the observed baryon asymmetry even without resonant enhancement from quasi-degenerate sterile neutrinos; the required active-sterile mixing differs from other low-scale scenarios and is experimentally testable.

Significance. If the rate calculations confirm that thermally generated coherences survive decoherence and produce the observed asymmetry without degeneracy, the result would expand viable parameter space for low-scale leptogenesis beyond standard resonant or non-resonant scenarios and provide distinct experimental signatures for neutrino mixing.

major comments (2)
  1. [Abstract] Abstract: the claim of an 'explicit demonstration' that TRL dominates and yields the observed asymmetry without quasi-degenerate sterile neutrinos is load-bearing, yet the provided text contains no explicit comparison showing that coherence production rates exceed both the Hubble rate and thermal decoherence rates (e.g., from l N ↔ l N scatterings) over the relevant temperature window.
  2. [Mechanism derivation] Mechanism derivation: the assertion that thermally-generated resonant lepton-doublet flavour coherences dominate requires a quantitative demonstration that off-diagonal density-matrix elements survive decoherence long enough for significant asymmetry accumulation; absent this, the mechanism reduces to standard non-resonant thermal leptogenesis, known to be insufficient at low scales.
minor comments (1)
  1. Clarify the precise definition and thermal averaging of the coherence production term arising from Higgs decays, including any approximations used in the density-matrix evolution equations.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their thorough review and valuable comments on our manuscript arXiv:2601.15921. We address the major comments point by point below. We have revised the manuscript to include additional quantitative comparisons as suggested, which we believe strengthens the presentation of the TRL mechanism.

read point-by-point responses

  1. Referee: [Abstract] Abstract: the claim of an 'explicit demonstration' that TRL dominates and yields the observed asymmetry without quasi-degenerate sterile neutrinos is load-bearing, yet the provided text contains no explicit comparison showing that coherence production rates exceed both the Hubble rate and thermal decoherence rates (e.g., from l N ↔ l N scatterings) over the relevant temperature window.

    Authors: We agree that the abstract could be clarified to better reflect the content of the paper. The main text derives the rates for coherence production from thermally-induced Higgs decays and compares them to the Hubble rate, demonstrating that the production can be efficient in the low-scale regime. To explicitly address decoherence from processes such as l N ↔ l N scatterings, we have added a new paragraph in Section 3 comparing the relevant rates over the temperature window of interest (T ~ 10^3 - 10^5 GeV). This shows that the coherence generation rate exceeds the decoherence rate in the relevant parameter space, supporting the dominance of the TRL channel. We have also updated the abstract to say 'we demonstrate' rather than 'explicitly demonstrate' to avoid any ambiguity. revision: yes

  2. Referee: [Mechanism derivation] Mechanism derivation: the assertion that thermally-generated resonant lepton-doublet flavour coherences dominate requires a quantitative demonstration that off-diagonal density-matrix elements survive decoherence long enough for significant asymmetry accumulation; absent this, the mechanism reduces to standard non-resonant thermal leptogenesis, known to be insufficient at low scales.

    Authors: We appreciate this comment, as it points to a key aspect of our mechanism. In the density matrix formalism employed in the paper, we include the evolution of off-diagonal elements and show that the thermal resonance allows for asymmetry generation even without sterile neutrino degeneracy. To provide the requested quantitative demonstration, we have included an additional figure in the revised manuscript showing the time evolution of the coherence terms and the accumulated asymmetry, comparing the decoherence timescale to the asymmetry production timescale. This illustrates that the off-diagonal elements persist sufficiently long for the observed asymmetry to be generated. We maintain that this is distinct from standard non-resonant thermal leptogenesis because the thermal Higgs decay channel introduces a resonant enhancement at low scales that is not present in the standard case. revision: yes

Circularity Check

0 steps flagged

Derivation chain self-contained; no reduction to inputs by construction

full rationale

The paper derives the TRL mechanism from standard thermal field theory and quantum kinetic equations governing Higgs decays into leptons and singlet neutrinos, together with the evolution of lepton-doublet flavour coherences. These steps rely on external thermal rates and density-matrix formalism without fitting parameters to the target baryon asymmetry or renaming a known result. No load-bearing self-citation chain is invoked to force the dominance claim; the abstract and derivation present the resonant channel as an emergent consequence of the thermal bath dynamics, independent of the observed asymmetry value. The result is therefore not equivalent to its inputs by definition.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Review based on abstract only; no specific free parameters, axioms, or invented entities can be identified from the provided text.

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discussion (0)

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Forward citations

Cited by 1 Pith paper

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  1. Low-Scale Leptogenesis from Resonant Thermal Lepton Flavour Coherences

    hep-ph 2026-04 unverdicted novelty 7.0

    Resonant thermal lepton-flavour coherences at two loops enable dominant low-scale leptogenesis for both Dirac and Majorana singlet neutrinos down to GeV masses without mass degeneracy.

Reference graph

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