{"id":"f6b39135-e210-4658-8ae5-9b68c0f98e68","arxiv_id":"2509.09609","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"HAWC and LHAASO diffuse gamma-ray data, modeled with prompt, inverse-Compton, absorption, and astrophysical background, produce the strongest constraints on decaying ultra-heavy dark matter above ~100 TeV.","lead":"Using TeV-PeV gamma-ray maps of the Galactic plane from HAWC and LHAASO, the authors set some of the strongest limits to date on dark matter particles heavier than 100 TeV. If the limits hold, they shrink the allowed parameter space for ultra-heavy dark matter candidates that colliders cannot reach.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"No significant objection identified: the background model is conservative, so the reader's concern would not weaken the central claim.","rationale":"I read the paper in good faith. The central claim is that LHAASO diffuse data, with conservative background modeling, yield the strongest gamma-ray constraints on decaying ultra-heavy dark matter. The reader identified the background model as the weakest assumption, but that concern is directionally incorrect. The 'Min' model is designed as a lower bound: it uses the lower envelope of local CR measurements and excludes unresolved sources. In the chi-square framework of Eq. (4), where only bins with model > data contribute, a larger background decreases the allowed DM signal, making limits stronger. Thus the reported limits are conservative; a higher true background would only improve them. The paper explicitly acknowledges this and compares with simultaneous works [80,81] in agreement. Other potential concerns (DM profile, absorption, statistical method) are either addressed or conservative in direction. The only remaining useful check is to verify that using a different, possibly higher background does not move the limits below IceCube; this would settle the robustness of the 'strongest constraints' claim. Therefore, no load-bearing objection is identified.","tokens_in":21749,"tokens_out":17735,"duration_ms":204659,"concrete_test":"Recompute the dashed decay-lifetime limits in Fig. 8 using a background model that includes an unresolved-source component (e.g., the model of Ref. [59] or the data-driven background of Ref. [81]). If the LHAASO with-background line remains at or above the IceCube limit for m>100 TeV, the central claim is confirmed; any shift should strengthen the limits, further supporting the claim.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The reader's weakest assumption is that a higher true astrophysical background (e.g., from unresolved sources) would weaken the LHAASO limits. The opposite is true: the chi-square method in Eq. (4) only penalizes model predictions exceeding the data, so a larger background component reduces the allowed DM signal, producing stronger (not weaker) lifetime limits. The 'Min' background from Refs. [39,40] is explicitly built as a lower bound on the hadronic emission and omits unresolved sources, so it underestimates the true background; the reported limits are therefore conservative. The paper's central claim—that LHAASO provides the strongest gamma-ray constraints on decaying ultra-heavy DM above ~100 TeV—is not threatened by the background model choice. No internal inconsistency or unsupported step was found in the signal modeling, absorption treatment, or statistical procedure.","agreement_with_reader":"disagree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper derives constraints on annihilating and decaying ultra-heavy dark matter (TeV-PeV masses) using recent HAWC and LHAASO measurements of the Galactic diffuse gamma-ray emission. The DM signal model includes prompt gamma rays from PPPC4DM/HDMSpectra, inverse-Compton emission from DM-produced e± propagated with DRAGON2/HERMES, and gamma-ray absorption on the CMB. Limits are set with a one-sided chi-square statistic, both without an astrophysical background and with a conservative 'Min' hadronic background model. The main results are 95% CL exclusion curves for τ+τ−, b bbar, and W+W− channels; the authors report that LHAASO provides the strongest gamma-ray constraints at high masses, competitive with IceCube, and that these constraints are less sensitive to the DM density profile than Galactic-center searches.","tokens_in":21983,"tokens_out":9281,"duration_ms":109879,"significance":"The topic is timely and the analysis is a useful addition. If the limits are valid, they extend indirect DM searches to tens of PeV using public data and state-of-the-art simulation codes. The inclusion of secondary IC emission and gamma-ray absorption is a genuine improvement over prompt-only treatments, and the deliberate use of a conservative background model is a strength. The paper also demonstrates that the derived limits are robust to the choice of DM density profile in the high-latitude regions. I agree with the stress-test note that the reader's weakest-assumption concern runs in the opposite direction: because Eq. (4) only penalizes model predictions above the data, a larger astrophysical background would make the DM upper limits stronger, not weaker. The 'Min' background is therefore a conservative choice. The central claim is credible, but the one-sided chi-square calibration and the fixed background treatment need additional support before the quantitative limits can be fully endorsed.","major_comments":[{"comment":"The test statistic sums only over bins with φ_mod_i > D_i, and the paper then identifies the 2σ limit with χ²=4, citing Refs. [62,63]. A truncated sum of this kind is not chi-square distributed, so the coverage of the resulting 95% CL limits is not guaranteed. Please provide a Monte Carlo calibration of the threshold, or replace the procedure with a profile-likelihood ratio; otherwise the numerical limits in Figs. 6-8 are not precisely calibrated confidence intervals.","section":"Eq. (4), Section III"},{"comment":"The 'with bkg' limits (dashed curves) use the 'Min' background model [39,40] as a fixed, additive component. Although the model is conservative by construction, the headline improvement of up to an order of magnitude is conditional on this single background realization. Please quantify the sensitivity by varying the background normalization/shape within the spread of local CR measurements, or by adding a plausible unresolved-source component, and show the resulting band on the dashed curves. This would support the claim of setting the 'strongest constraints' without overstating the robustness.","section":"Section IV, Figs. 6-8"},{"comment":"The paper says it uses LHAASO data from both WCDA and KM2A detectors, but it never specifies how the two data sets enter the chi-square sum in Eq. (5). Are they fit jointly with separate energy-bin lists? Is the energy overlap between WCDA and KM2A handled to avoid double counting? Please state the exact regions, energy bins, and any treatment of correlated systematics; this is needed to reproduce the reported LHAASO limits.","section":"Sections II and IV"}],"minor_comments":[{"comment":"The phrase '300 hundred GeV' should be '300 GeV' or 'hundreds of GeV'.","section":"Abstract / Section II"},{"comment":"The bottom panel x-axis is labeled 'Galactic longitude [deg]', but the range (−10° to 10°), the caption, and the text indicate it shows a latitude profile. Relabel as 'Galactic latitude [deg]'.","section":"Figure 5"},{"comment":"The sentence ending 'because the prompt emission drops off rapidly below the.' is incomplete; please finish the sentence.","section":"Section III"},{"comment":"The text mentions a Moore profile in the discussion of DM distribution uncertainty, but Appendix A and Fig. 9 only show Einasto, NFW, and Burkert. Either add the Moore comparison or remove the mention.","section":"Section IV / Appendix A"},{"comment":"References [53] and [54] appear to be identical (Leung & Ng, same arXiv number). Merge or correct.","section":"References"},{"comment":"The claim that neglecting Galactic radiation fields changes absorption by only ~10% should be supported with a brief explanation or a numerical check, and the sign of the effect should be stated.","section":"Section III, gamma-ray absorption"}],"recommendation":"major_revision","confidential_remarks":"The paper overlaps in scope with Refs. [80,81], which appeared just before submission and which the authors explicitly acknowledge and state agree with their results. The overlap is not disqualifying, but the editor may wish to verify that the present work's additional ingredients (combined HAWC+LHAASO, secondary IC, absorption) are sufficiently distinct after the revision. The main technical concerns are the calibration of the one-sided chi-square statistic and the fixed background model; these are fixable and do not call into question the overall physical picture."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Quick take: this is a solid constraints paper. The authors combine recent HAWC and LHAASO diffuse measurements with a fairly complete treatment of prompt, inverse-Compton, and absorption, and they use that to set new limits on ultra-heavy dark matter. The headline result—LHAASO data give the best gamma-ray limits on decaying DM above ~100 TeV, competitive with IceCube—holds up.\n\nThe genuinely new part is the joint analysis of the WCDA and KM2A data with a self-consistent propagation setup (DRAGON2/HERMES) and the inclusion of a background model. The paper is transparent about the ingredients and the simultaneous work in Refs. [80,81] is acknowledged. The agreement with those results is reassuring.\n\nI want to flag one thing about the background. The reader's concern that a higher true background would weaken the limits is backwards. Since the chi-square in Eq. (4) only penalizes model predictions that exceed the data, a larger background contribution means the observed flux allows even less DM signal. The 'Min' model is deliberately a lower bound on the hadronic emission, so the reported limits are conservative. This is worth stating clearly because it is the main thing I would otherwise worry about.\n\nThe softer spots are minor. The one-sided chi-square method is non-standard; it would help to justify the threshold choice, but it errs on the side of conservatism. The annihilation limits depend on the DM density profile by up to a factor of three, but the paper quantifies this and the decay limits are essentially untouched. Background systematics are not propagated, but given the conservative direction of the model choice, that is more a clarity issue than a correctness issue.\n\nBottom line: this is a useful, well-executed analysis that will be a reference for VHDM constraints. It deserves proper peer review; I would be happy to referee it.","headline":"Solid constraints paper; the background-model worry is a non-issue because the limits are conservative, and the main claims hold up.","tokens_in":22456,"tokens_out":3755,"would_cite":true,"duration_ms":39683,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"Using the TeV–PeV diffuse gamma-ray glow of the Galactic plane as measured by LHAASO and HAWC, this paper sets the strongest current constraints on decaying ultra-heavy dark matter—excluded lifetimes below about 10^29 seconds above 100 TeV—","keywords":["ultra-heavy dark matter","dark matter decay","dark matter annihilation","diffuse gamma-ray emission","Galactic plane","LHAASO","HAWC","inverse Compton emission"],"falsifier":"Recompute the limits using an alternative background model that includes an unresolved-source component normalized to the data and check whether the reported lifetime limits above 10^29 s survive; if the limits drop by more than a few tens of percent, the background choice is the deciding factor.","tokens_in":21664,"feed_emoji":"🌌","tokens_out":6251,"duration_ms":66785,"temperature":0.7,"pith_summary":"The paper tries to establish that ultra-heavy dark matter particles with masses from a few TeV to tens of PeV can be probed more strongly than ever before using measurements of the diffuse gamma-ray glow of the Galactic plane at TeV–PeV energies. It combines the LHAASO and HAWC diffuse-emission data with a full model of dark-matter-induced gamma rays, including prompt photons, secondary inverse-Compton emission from dark-matter-produced electrons and positrons, and absorption of very-high-energy photons. Adding a conservative astrophysical background model strengthens the limits by up to an order of magnitude. The resulting decay-lifetime constraints, around 10^29 seconds, are competitive with IceCube and, above certain masses, become the strongest available. If true, dark matter decaying into standard particles must be extremely long-lived, and future observatories like CTA and SWGO could push the bounds further.","feed_headline":"LHAASO data push dark-matter decay lifetime past 10^29 s","feed_subtitle":"TeV–PeV diffuse maps, after background subtraction, set the strongest ultra-heavy dark-matter bounds yet.","key_machinery":"The load-bearing combination is the diffuse Galactic plane datasets of LHAASO (WCDA and KM2A) and HAWC, together with a three-part emission model: prompt gamma rays from dark-matter annihilation or decay, inverse-Compton gamma rays from the secondary electrons and positrons propagated through the Galaxy, and gamma-ray absorption by photon-photon pair production on the cosmic microwave background. On top of this, the strongest limits use a deliberately conservative 'Min' model of the astrophysical hadronic diffuse emission (built to fit the lower envelope of local cosmic-ray measurements) as the background. The background subtraction is what turns the data into an order-of-magnitude stronger","core_discovery":"On its own terms, the paper's central claim is that the diffuse gamma-ray emission measured from the Galactic plane by LHAASO (WCDA+KM2A) and HAWC, in the energy range roughly 0.3 TeV to 1 PeV, provides the most powerful current gamma-ray probe of very heavy dark matter. For decaying dark matter, the paper derives lower limits on the lifetime that reach about 10^29 s for masses above 100 TeV, improving on previous gamma-ray bounds and matching the best neutrino limits. For annihilating dark matter, the limits become the strongest gamma-ray constraints above about 1000 TeV. These results follow from consistently modelling the prompt gamma rays, the secondary inverse-Compton emission from the","pith_inferences":["Because the paper's no-background (conservative) limits are weaker than some existing bounds at intermediate masses, the competitive annihilation claim rests heavily on the adopted 'Min' background model; a reader comparing the dashed and solid curves before citing should weigh this dependence.","The 'Min' model fits the lower envelope of cosmic-ray measurements and omits unresolved sources, so if future surveys reveal a substantial population of unresolved point sources, the reported 'strongest constraints' would weaken proportionally.","The paper's own morphological comparison shows a pure decaying-DM signal does not match the LHAASO latitude profile, suggesting dark matter is at most sub-dominant; the constraints are therefore best read as upper limits on DM contributions rather than hints of a signal.","The secondary inverse-Compton emission is computed with a state-of-the-art propagation code; different propagation assumptions could shift the secondary contribution and thus the limits, especially for leptonic channels, though the paper finds the effect is spectator for the LHAASO region."],"forward_implications":["If decaying dark matter exists with lifetime below about 10^29 s and mass above about 100 TeV, its gamma-ray signature would already appear in the LHAASO Galactic plane data; the observed smooth power-law spectra therefore exclude such configurations.","The inclusion of the astrophysical background model improves the constraints by up to an order of magnitude, meaning that better background models directly translate into stronger dark-matter limits.","The constraints from these mid-longitude diffuse regions are largely insensitive to the dark-matter density profile, especially for decay, reducing a common source of systematic uncertainty.","The same method applied to future CTA and SWGO data should push sensitivity to higher masses and lower cross sections or longer lifetimes.","Annihilation limits above 1000 TeV are competitive with IceCube bounds and can dominate in particular channels."],"fun_headline_variants":["LHAASO gamma rays set dark matter decay lifetime >10^29 s","TeV-PeV diffuse emission bounds ultra-heavy dark matter decay","Galactic gamma maps push dark matter lifetime to 10^29 s","Ultra-heavy DM decay constrained to >10^29 s by LHAASO","Diffuse gamma-ray data tighten limits on ultra-heavy dark matter"],"cache_read_input_tokens":2304,"weakest_assumption_plain":"The strongest constraints assume the 'Min' hadronic background model—which fits the lower envelope of cosmic-ray measurements and neglects unresolved sources—is the true astrophysical diffuse emission; if the real background is higher, the dark-matter limits weaken accordingly.","fun_headline_variants_meta":{"raw":{"variants":["LHAASO gamma rays set dark matter decay lifetime >10^29 s","TeV-PeV diffuse emission bounds ultra-heavy dark matter decay","Galactic gamma maps push dark matter lifetime to 10^29 s","Ultra-heavy DM decay constrained to >10^29 s by LHAASO","Diffuse gamma-ray data tighten limits on ultra-heavy dark matter"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.001038,"raw_usage":{"total_tokens":4232,"prompt_tokens":801,"completion_tokens":3431,"prompt_tokens_details":{"cached_tokens":256},"prompt_cache_hit_tokens":256,"prompt_cache_miss_tokens":545,"completion_tokens_details":{"reasoning_tokens":3334}},"tokens_in":545,"tokens_out":3431,"duration_ms":28914,"temperature":1.0,"reasoning_tokens":3334,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-04T18:43:51.484752+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Recompute the limits using an alternative background model that includes an unresolved-source component normalized to the data and check whether the reported lifetime limits above 10^29 s survive; if the limits drop by more than a few tens of percent, the background choice is the deciding factor.","supporting_citations":[],"review_version":1}