{"id":"53b3645f-fd06-4d1a-a5fd-7d51eab568f0","arxiv_id":"2512.09997","paper_version":2,"verdict":"REJECT","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"high","formal_verification":"none","parameter_count":0,"one_line_summary":"Diffuse Galactic gamma-ray data strongly limit the couplings of gravitationally produced decaying dark matter, and the paper claims an oscillation-based bound on massive dark photons.","lead":"This letter uses gamma-ray maps of the Milky Way from LHAASO and Fermi-LAT to bound the decay of dark matter produced only by gravity, pushing required couplings below 10^-26 for TeV-to-PeV masses. It is a sharp test of 'ultraviolet freeze-in' dark matter and of the simplest graviton-mediated production scenarios.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Oscillation bound (Fig. 2) uses decay-flux normalization for a stable species and probes a region where the dark photon would have decayed long before today.","rationale":"The reader correctly identifies the use of τ_U in the oscillation flux as the weakest assumption. My independent reading confirms this: Eq. (9) multiplies the DM decay flux by a dimensionless probability, and the definition Φ_X = D/(4π m_X τ_U) is only appropriate for a real decay with lifetime τ_U. The oscillation probability does not provide such a rate. The additional check on the lifetime of the dark photon makes the problem worse: the parameter space excluded by Fig. 2 is one where the dark photon would have decayed almost immediately, so applying a stable-DM oscillation calculation is inconsistent. Therefore, the advertised closure of unconstrained parameter space is not supported. The decay bounds in Fig. 1 (for RHNs, pNGBs, and the non-minimally coupled scalar) rely on the well-established decay-flux formula and may well be correct; however, the central claim as stated in the abstract includes the oscillation result, so the paper as written should not be accepted.","tokens_in":11054,"tokens_out":13383,"duration_ms":136101,"concrete_test":"Take a representative point in the excluded region of Fig. 2, e.g., m_X = 10 GeV, ε = 10^-3. Compute the total decay width using Eq. (8) (including hadronic R factor) and compare τ_X = 1/Γ_X with τ_U = 4.35×10^17 s. If τ_X ≪ τ_U, then the dark photon cannot be DM there, and the oscillation bound is vacuous. Additionally, re-derive the expected photon flux for a stable dark-photon population from the propagation equations (including the non-relativistic dispersion and local plasma density), and compare it with the flux used in the paper; if the flux normalization changes by orders of magnitude, the exclusion curve of Fig. 2 shifts correspondingly.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The Fig. 2 oscillation bound is built on an invalid flux normalization. In the text, the flux is set to Φ_X = D/(4π m_X τ_U) (Eq. 9 and subsequent line), which is the standard expression for a species decaying with lifetime τ_U. But the conversion probability in Eq. (29), P_{X→γ} = 2ε², is a dimensionless constant after averaging; it is not a decay rate and does not introduce any τ_U dependence. A stable dark-photon population would yield a photon flux proportional to the line-of-sight integral of the DM number density times the conversion probability, not the decay flux formula. Moreover, the excluded region (ε > 10^-3 for m_X > 10 GeV) corresponds to dark-photon lifetimes far shorter than τ_U: using Eq. (8) at m_X = 10 GeV and ε = 10^-3 gives τ_X ~ 10^-17 s, many orders of magnitude below the age of the Universe. Such dark photons would have decayed promptly and cannot constitute the DM today. Hence the oscillation constraint is not physically applicable, and the claim that it closes previously unconstrained parameter space is unsupported.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript derives constraints on gravitationally produced decaying dark matter using LHAASO and Fermi-LAT diffuse Galactic gamma-ray observations. Four benchmark models are considered: a kinetically mixed dark photon, a heavy right-handed neutrino, a pNGB coupled to electroweak gauge bosons, and a non-minimally coupled scalar. The authors use a standard DM-decay flux formula with an NFW halo profile and compute photon spectra with HDMSpectra to set upper limits on the relevant couplings, and they add a separate photon–dark-photon oscillation constraint. The claimed results are extremely small couplings (≲10^-30) for heavy DM and a new oscillation-based exclusion of kinetic mixing ε≳10^-3 for m_X≳10 GeV.","tokens_in":11384,"tokens_out":9064,"duration_ms":92808,"significance":"If the decay-mode constraints in Fig. 1 hold, the paper provides useful, model-specific bounds on gravitational DM portals using public data and a standard decay-flux pipeline. The production framework is taken from the literature and the gamma-ray data are external, so I do not see a circularity problem. The main weakness is the oscillation analysis: it applies a decay-flux normalization to a stable species and excludes a region where the dark photon would already have decayed, so the Fig. 2 claim is unsupported as it stands. The Fig. 1 constraints are nevertheless valuable and worth publishing after a substantial revision.","major_comments":[{"comment":"Eq. (9) sets Φ_X = D/(4π m_X τ_U), which is the standard flux for a decaying species (Eq. 17). But in this section P_{X→γ} in Eq. (29) is a dimensionless conversion probability after averaging, not a decay rate. For a stable dark-photon DM population, the photon flux is a line-of-sight integral involving ρ_DM/m_X and the differential conversion probability dP/dz, not D/(4π m_X τ_U). No derivation of the integrated conversion flux is given, and the insertion of τ_U is unjustified. The Fig. 2 bound is therefore not derived from the stated physics.","section":"Photon–dark photon oscillation, Eq. (9)"},{"comment":"Fig. 2 excludes ε≳10^-3 for m_X≳10 GeV. However, Eq. (8) gives τ_X ~ 10^-17 s at m_X = 10 GeV and ε = 10^-3, so the excluded dark photons would have decayed long before the present epoch and cannot constitute the DM population assumed in Eq. (9). The gray τ_X < τ_U region in Fig. 1 would in fact cover essentially the entire oscillation-excluded area. The oscillation constraint must be restricted to dark photons with τ_X > τ_U and must use a correct propagation/absorption treatment; otherwise the claim of closing previously unconstrained parameter space is unsupported.","section":"Photon–dark photon oscillation, Fig. 2"},{"comment":"The non-minimally coupled scalar benchmark is not self-contained: the Jordan-frame action in Eq. (13) does not display the scalar S kinetic/mass term or the explicit ξ M_P S R coupling used in the text, and the production rate γ_S = ξ^4 T^8/M_P^4 that leads to Eq. (15) is introduced without derivation. Since the lower-right panel of Fig. 1 and the corresponding abstract claim depend on these inputs, the authors should provide the complete action and either derive or precisely cite the origin of γ_S and Eq. (15).","section":"Gravity induced DM decay, Eqs. (13)–(15)"}],"minor_comments":[{"comment":"Eq. (13) contains typographical inconsistencies (e.g., the '/∂ω' term) and lacks the S kinetic/mass terms; please re-check the displayed action.","section":"Eq. (13)"},{"comment":"The statistical procedure behind the 'combined LHAASO and Fermi-LAT' constraints is not described. Please state the confidence level, binning, and background treatment, or cite the exact analysis chain used to produce the blue curves.","section":"Fig. 1 and 'combined' constraints"},{"comment":"The abstract's claim '≲O(10^-30) for DM masses ≳O(TeV)' is too broad: the figure and text quote O(10^-26) at O(1 PeV) for the dark photon and RHN, with 10^-30 applying at much larger masses. Please qualify the mass range.","section":"Abstract and Fig. 1"},{"comment":"Sec. II heading contains the typo 'electoweak'. Also, the cross-reference in Eq. (9) to 'Sec. I for details' should refer to the appendix containing the conversion-probability derivation.","section":"Heading and cross-reference"},{"comment":"Fig. 2 would be much more informative if the τ_X = τ_U curve were overlaid, so the reader can see which excluded region corresponds to dark photons that survive to the present.","section":"Fig. 2"}],"recommendation":"major_revision","confidential_remarks":"The oscillation result is the main advertised new constraint and is not physically meaningful as written; it cannot be fixed by wording alone and needs either a full rederivation of the line-of-sight conversion flux with the τ_X > τ_U requirement, or removal of Fig. 2 and the related abstract claim. The decay-mode section is standard and appears sound, so I recommend major revision rather than rejection. I see no inappropriate citation behavior beyond the usual practice of citing one's own related work."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The short version: the decay-mode constraints on gravitationally produced DM are solid, useful, and probably correct. The oscillation-based bound that the abstract advertises as a main result is not; it uses a decay flux for a stable species and excludes a region where the dark photon would have decayed long before today. The paper needs major revision, but it deserves a referee's time.\n\nWhat's actually new: applying combined LHAASO and Fermi-LAT diffuse gamma-ray data to four gravitational DM benchmarks—dark photon, RHN, pNGB, non-minimally coupled scalar—and deriving couplings at the 10^-26–10^-31 level for TeV–PeV masses. The production yield is taken from the UV freeze-in literature (with some self-citations, but not used as fitted inputs, so no circularity), the decay spectra come from HDMSpectra, and the Galactic flux is standard NFW. That part of the paper is a legitimate new application and likely sound.\n\nThe soft spot is Fig. 2 and the oscillation claim. The text sets Phi_X = D/(4π m_X tau_U) in Eq. (9) for the photon–dark photon oscillation channel. That is the flux for a species decaying with lifetime tau_U, but the conversion probability P=2ε^2 is a dimensionless constant, not a decay rate. A stable dark photon population converting to photons would give a flux proportional to the line-of-sight integral of density times conversion probability, not the decay formula. On top of that, the excluded region (ε≳10^-3 for m_X≳10 GeV) corresponds via Eq. (8) to tau_X ~ 10^-17 s, many orders of magnitude below the age of the Universe. Those dark photons would have decayed to e+e- before today and cannot be the DM. So the constraint is not physically applicable as stated.\n\nMinor issue: the abstract quotes couplings ≲10^-30, while the text gives 10^-26 for dark photon/RHN and 10^-31 for pNGB. That's cosmetic but should be fixed.\n\nThe decay bounds alone are worth publishing after the oscillation section is either corrected or removed. I would send this to peer review with a clear request for major revision. It is not a desk reject.","headline":"Decay constraints on gravitational DM are solid; the oscillation bound is a load-bearing error that the paper's own lifetime condition contradicts.","tokens_in":11816,"tokens_out":5682,"would_cite":true,"duration_ms":58035,"reading_group":"maybe","serious_thinker":"no","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":["95.35.+d","95.85.Pw"],"model":"deepseek-v4-flash","headline":"Galactic gamma-ray data can constrain gravitationally produced decaying dark matter to couplings below 10^-30.","keywords":["gravitational dark matter","UV freeze-in","diffuse Galactic gamma-ray emission","LHAASO","Fermi-LAT","decaying dark matter","dark photon oscillation","kinetic mixing"],"falsifier":"Compute the expected gamma-ray intensity from a stable dark photon dark-matter population by integrating the local number density n_X(s) times the conversion probability per unit length (≈ 2ε² once the oscillation length is exceeded) along the line of sight toward the inner Galactic plane, and compare the resulting bound on ε with the paper's ε ≲ 10^-3; if the corrected bound differs by more than an order of magnitude, the oscillation exclusion is driven by the flux normalization rather than the data.","tokens_in":10983,"feed_emoji":"🌌","tokens_out":15394,"duration_ms":134888,"temperature":0.7,"pith_summary":"The paper claims that diffuse Galactic gamma-ray observations by LHAASO and Fermi-LAT are sensitive enough to constrain dark matter produced only through gravitational interactions during reheating and later decaying into photons. For three benchmark candidates (dark photon, right-handed neutrino, pseudo–Nambu–Goldstone boson), the combined data force the effective coupling to the visible sector below 10^-30 for masses above the TeV scale, while a non-minimally coupled scalar is limited to roughly 10^-10 and below. The same data, through photon–dark photon oscillations, exclude kinetic mixing above about 10^-3 for dark photon masses above 10 GeV, closing a region not previously covered by laboratory experiments. If correct, these bounds make Galactic gamma-ray telescopes the most sensitive probe of ultra-feeble couplings in this mass range.","feed_headline":"Galactic gamma rays bound dark-matter couplings to 10^-30","feed_subtitle":"Diffuse Galactic plane data from LHAASO and Fermi-LAT reach far below laboratory sensitivity.","key_machinery":"The central object is the decaying-dark-matter gamma-ray flux integral ϕ(E) = D/(4π m τ) dN/dE, where D = ∫ ρ_NFW ds over the inner Galactic plane (≈ 3×10^19 GeV/cm²) and dN/dE is the photon spectrum per decay. For the oscillation case, the machinery is the averaged kinetic-mixing conversion probability P_{X→γ} = 2ε², combined with the incoming dark photon flux Φ_X = D/(4π m_X τ_U). The gravitational production rate γ ∝ T^8/M_P^4 fixes the reheating temperature needed for the observed relic abundance, linking the particle physics couplings to early-Universe cosmology.","core_discovery":"For each of four dark-matter candidates produced by gravity (vector dark photon, right-handed neutrino, pseudo–Nambu–Goldstone boson, non-minimally coupled scalar), the paper computes the gamma-ray flux from dark-matter decay in the Milky Way using the standard line-of-sight integral over the NFW density profile and the per-decay photon spectra, then compares with the diffuse emission measured by Fermi-LAT (GeV–TeV) and LHAASO (TeV–PeV). The central result is that the upper limits on the coupling to the visible sector reach ε, the RHN Yukawa coupling, and C_ii/f_φ ≲ 10^-30–10^-31 for dark-matter masses ≳ TeV, and ξ ≲ 10^-10–10^-14 for the non-minimally coupled scalar. Using the averaged conv","pith_inferences":["The oscillation bound in Fig. 2 rests on treating a stable dark photon population as if it decayed with a Hubble-time lifetime; a proper line-of-sight conversion integral for a stable relic could shift the ε limit by orders of magnitude, so the exclusion should be checked against the full propagation treatment.","Since the gravitational production rate fixes the reheating temperature for a given mass and spin, these gamma-ray bounds can be reinterpreted as upper limits on the reheating temperature for each benchmark scenario if the dark matter is to remain unobserved.","The same flux formalism applies to axion-like particles with two-photon couplings or to other feebly interacting particles produced gravitationally, so the approach likely extends beyond the four candidates considered here.","A future detection of a spectral cutoff or line-like feature in the diffuse Galactic gamma-ray spectrum could be cross-checked against the predicted shape from gravitational dark-matter decay, turning the constraint into a discovery channel."],"forward_implications":["If the bounds hold, theories in which TeV–PeV dark matter is produced gravitationally and decays to photons with couplings above ~10^-30 are excluded; only models with such ultra-feeble couplings remain viable.","The oscillation limit ε ≲ 10^-3 for m_X ≳ 10 GeV closes a dark-photon mass window that colliders and beam dumps cannot reach, making gamma-ray telescopes the primary probe of that parameter space.","Because the constraints depend on the decay channel, a better measurement of the diffuse Galactic gamma-ray spectrum could in principle distinguish which final states dominate the decay.","For the non-minimally coupled scalar, the bound ξ ≲ 10^-10 at TeV mass directly limits gravitational-strength interactions between the dark scalar and Standard Model particles.","The constraints are conservative in the sense that adding conventional astrophysical sources such as supernova remnants and pulsars to the diffuse emission model would strengthen the bounds, as the paper notes."],"fun_headline_variants":["Gamma-ray data tighten dark matter coupling bounds to 10^-30","LHAASO and Fermi-LAT set limits on gravity-produced dark matter","Gravitational dark matter faces gamma-ray constraints","Dark matter couplings probed down to 10^-30 by gamma rays","Galactic gamma rays narrow dark matter decay models"],"cache_read_input_tokens":2304,"weakest_assumption_plain":"The dark-photon oscillation constraint assumes the incoming dark photon flux is Φ_X = D/(4π m_X τ_U), the flux a species decaying with the age of the Universe would produce; a stable dark photon population converts with probability 2ε² along the line of sight, and using the correct stable-population flux could change the bound by orders of magnitude.","fun_headline_variants_meta":{"raw":{"variants":["Gamma-ray data tighten dark matter coupling bounds to 10^-30","LHAASO and Fermi-LAT set limits on gravity-produced dark matter","Gravitational dark matter faces gamma-ray constraints","Dark matter couplings probed down to 10^-30 by gamma rays","Galactic gamma rays narrow dark matter decay models"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000241,"raw_usage":{"total_tokens":1350,"prompt_tokens":728,"completion_tokens":622,"prompt_tokens_details":{"cached_tokens":256},"prompt_cache_hit_tokens":256,"prompt_cache_miss_tokens":472,"completion_tokens_details":{"reasoning_tokens":536}},"tokens_in":472,"tokens_out":622,"duration_ms":6352,"temperature":1.0,"reasoning_tokens":536,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-03T17:19:58.716812+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Compute the expected gamma-ray intensity from a stable dark photon dark-matter population by integrating the local number density n_X(s) times the conversion probability per unit length (≈ 2ε² once the oscillation length is exceeded) along the line of sight toward the inner Galactic plane, and compare the resulting bound on ε with the paper's ε ≲ 10^-3; if the corrected bound differs by more than an order of magnitude, the oscillation exclusion is driven by the flux normalization rather than the data.","supporting_citations":[],"review_version":1}