{"id":"016025b4-65fc-4d36-91e1-0e716933a73d","arxiv_id":"2412.00180","paper_version":2,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":2,"one_line_summary":"Using INTEGRAL x-ray and AMS-02 positron data, the authors set lower limits on dark photon and scalar dark matter decay lifetimes from 10^25 to 10^29 seconds across 1 MeV to 2 TeV masses.","lead":"This paper searches for signs of dark matter decaying into ordinary particles using two telescopes: INTEGRAL for low masses and AMS-02 for high masses. It finds no signal and sets the strongest limits yet on how long dark photons and scalar dark matter can live before decaying. A smart generalist might read it because it narrows down the possible ways dark matter could interact with our world and points to where future experiments should look.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The AMS-02 constraints hinge on the completeness of the fixed Ref [116] background model; only 5 parameters are refit, so an unmodeled pulsar spectral break or spatial distribution could absorb the smooth scalar DM signal and substantially weaken the quoted lifetime limits.","rationale":"The paper's central claim is a set of exclusion limits on DM decay lifetimes. For exclusions to be valid, the astrophysical background must be sufficiently well known that the DM template cannot be absorbed by unmodeled background freedom. The AMS-02 analysis is the source of the strongest limits (10^29 s) and the only constraint above 10 GeV, so its background assumptions are the load-bearing element. The reader flagged the pulsar background in Ref [116]; I agree, but sharpen it: the paper refits only five parameters, and the fixed components include the pulsar spatial distribution and the spectral shape beyond a single power law. Because the scalar DM positron spectrum is smooth, it is precisely the kind of signal that can be degenerate with a flexible pulsar background. A broken power law or a revised pulsar distribution is a motivated alternative that could change the limits; the concrete test quantifies this. Other potential concerns (ignoring 511 keV annihilation, neglecting loop-induced scalar decays, fixed DM halo profile) either go in the direction of making limits conservative or shift limits by factors of a few, not orders of magnitude. The INTEGRAL constraints are less exposed because the FSR spectral shape is distinctive and the background template is public. Therefore, the conditional acceptance is appropriate, pending a robustness check of the AMS-02 background model.","tokens_in":22494,"tokens_out":13179,"duration_ms":129924,"concrete_test":"Re-run the AMS-02 analysis for scalar DM at m=30, 100, 300 GeV with two alternative background models: (1) a broken power-law pulsar injection spectrum with free break energy and two spectral indices, and (2) the ATNF pulsar catalog spatial distribution instead of the Lorimer distribution, refitting the same 5+new parameters. If the 95% CL lifetime limits shift by more than a factor of 3 for any mass, the quoted scalar DM constraints are not robust to pulsar modeling assumptions; if they shift by less, the concern is resolved.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"Section III B 2 states that after adding DM templates, only the diffusion coefficient, diffusion spectral index, and three pulsar parameters (spectral index, cutoff energy, formation rate) are refit. Everything else in the Ref [116] background—pulsar spatial distribution, injection spectral shape beyond a single power law with cutoff, secondary positron production, solar modulation—is held fixed. For scalar DM the positron spectrum is smooth (Fig. 6, right), and the scalar limits (10^26–10^27 s) are already noted to be weaker because of degeneracy with the pulsar component. If the true pulsar population has a spectral break or a different spatial distribution than the Lorimer model, the refit could absorb part of the DM signal, shifting the 95% CL limits by orders of magnitude. The dark photon peak at half the DM mass is less degenerate, so the headline 10^29 s constraint is more robust, but the scalar DM claim and the sub-100 GeV dark photon limits are directly exposed to this systematic. The paper does not vary the fixed background components or quantify their uncertainty, so the central claim is conditional on Ref [116] being complete.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper studies the late-time decay of bosonic dark matter into Standard Model final states, focusing on two benchmark models: dark photons with kinetic mixing and scalars with Higgs-like Yukawa couplings. For dark matter masses between 1 MeV and 10 GeV, the authors use 16 years of INTEGRAL/SPI x-ray data; for masses between 10 GeV and 2 TeV, they use AMS-02 positron data. They compute model-dependent branching ratios from the Lagrangians in Section II, generate DM decay spectra with Hazma, FSR formulas, and CosmiXs, add DM templates to empirical astrophysical background models, and derive 95% CL upper limits on the decay rate, which translate to lower limits on the DM lifetime. The paper reports no evidence for a dark matter signal and quotes lifetime limits reaching about 10^25 s below 10 GeV and up to about 10^29 s for dark photons near 10 GeV, with corresponding constraints on the kinetic mixing and scalar mixing angle that improve on the age-of-Universe constraint by several orders of magnitude. It also compares the model-specific results with generic single-channel e+e- and bb decay analyses.","tokens_in":22727,"tokens_out":8033,"duration_ms":81659,"significance":"If the limits hold, they are competitive and in several mass ranges world-leading for these benchmark models, and the branching-ratio calculation is a useful public resource for other vector and scalar portal models. I credit the authors for the careful treatment of the full decay widths, for using a publicly available INTEGRAL template, for the explicitly conservative FSR-only treatment in the 1.5-10 GeV interval, and for the clear comparison to single-channel decay models. The analysis is not circular in the way that is sometimes found in dark matter fits: DM templates are added to an empirical astrophysical background rather than being derived from the parameters that the background fit determines. The main caveat is the completeness of the fixed AMS-02 background model from Ref. [116]; this is a systematic uncertainty rather than a flaw in the decay-width calculation, and it is quantified below.","major_comments":[{"comment":"The AMS-02 constraints are obtained by re-fitting only the diffusion coefficient, the diffusion spectral index, and three pulsar parameters (spectral index, cutoff energy, formation rate) on top of the fixed background model of Ref. [116]. The pulsar spatial distribution (Lorimer model), the injection spectral shape beyond a single power law with cutoff, the secondary positron calculation, and solar modulation are all held fixed. For scalar dark matter the injected positron spectrum is smooth (Fig. 6, right), and the paper itself notes that the scalar limits (about 10^26-10^27 s) are weakened by degeneracy with the pulsar component. An unmodeled pulsar spectral break or an alternative pulsar spatial distribution could therefore absorb part of a scalar DM template and shift the quoted 95% CL lifetime limits by orders of magnitude; the same concern applies to the sub-100 GeV dark photon limits, which are less peaked than the high-mass dark photon signal. I request a stability test that varies the fixed background components (for example, pulsar spectral break, spatial distribution, or an alternate pulsar population model) or otherwise quantifies the systematic uncertainty in the AMS-02 limits. Without such a test, the central claim of strong AMS-02 constraints is conditional on the completeness of Ref. [116].","section":"III B 2"},{"comment":"The headline lifetime limits are presented as smooth curves spanning the full 1 MeV-2 TeV range, but the two experiments probe very different quantities: INTEGRAL uses the prompt x-ray flux from final-state radiation while AMS-02 uses propagated positrons. The paper should state more explicitly how the 10 GeV boundary is handled and whether the INTEGRAL and AMS-02 limits at that boundary are consistent, since the quoted 'up to 10^29 s' is driven by AMS-02 while the sub-10 GeV curves are driven by INTEGRAL. A reader could otherwise interpret the combined figure as a single continuous constraint from a single observable.","section":"Section IV / Fig. 7"}],"minor_comments":[{"comment":"Several exponents are typeset as inline digits rather than superscripts (for example, '10 25 s' in the abstract and '1029' in Section IV), which makes the numbers hard to read and could create ambiguity in the lifetime limits.","section":"Abstract and throughout"},{"comment":"The caption contains the typo 'T op', and the panel labels contain the corrupted glyph sequence 'I/glyph1197TEGRAL' in place of 'INTEGRAL'; these should be corrected in the final figure.","section":"Fig. 7 caption and panel labels"},{"comment":"The dwarf galaxy name is rendered as 'LeoT' both in the figure legend and in the text discussion; it should be 'Leo T'.","section":"Fig. 9 and Section IV"},{"comment":"The sentence 'T.T.Q.N is also grateful for the supported by the COST Action COSMIC WISPers' is ungrammatical and should be rewritten.","section":"Acknowledgments"},{"comment":"There is a typo 'suppressed compared to the the direct production of e+e-' that should read 'suppressed compared to the direct production'.","section":"Section IV"}],"recommendation":"major_revision","confidential_remarks":"The key risk in this manuscript is the AMS-02 background model, and one of the present authors is also a co-author of Ref. [116]. I do not see this as circularity, because the background model is an empirical fit to AMS-02 data that is independent of the DM templates. However, the shared authorship increases the responsibility to demonstrate that the constraints are not driven by the fixed parts of that model. The paper's own admission that the scalar DM spectrum is degenerate with the pulsar component suggests that broadening the profile likelihood or testing alternate pulsar prescriptions is necessary before the quoted scalar and sub-100 GeV dark photon limits can be regarded as robust. The decay-width and INTEGRAL parts of the paper are, in my reading, sound and well within the scope of the journal."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Two things to know. First, the paper's main value is the complete, mass-dependent branching ratios for dark photon and scalar DM decay, applied to both INTEGRAL x-ray and AMS-02 positron data across 1 MeV to 2 TeV. That combination is new, and Appendix B's comparison with single-channel assumptions shows that using e+e− or bb can misestimate lifetimes by orders of magnitude—a genuinely useful result for the field. Second, the AMS-02 constraints are only as credible as the background model they inherit. The analysis takes the John & Linden (2021) pulsar-plus-diffusion model as fixed and refits only five parameters when adding DM templates. The stress-test note is right: scalar DM produces a smooth positron spectrum that is degenerate with the pulsar component, so an unmodeled spectral break or spatial distribution could shift those limits by orders of magnitude. The dark photon's sharp line at half the DM mass is much more robust. The paper does not quantify this systematic, and the fitting code is not released, which would have helped. That said, the authors are honest about their conservative choices—FSR-only for 1.5–10 GeV, for example—and the decay-width formulas and hadronic form factors reproduce earlier work, so the core physics is solid. The INTEGRAL analysis uses public templates and a well-tested MCMC pipeline. One minor presentational issue: the abstract's headline, 10^29 s for GeV-scale DM, is the dark photon number; scalar DM limits plateau around 10^26–10^27 s, so the abstract can be over-read if applied to both models. This paper is for the indirect-detection community and for model-builders who need benchmark constraints on dark photon and scalar mediators. It deserves a serious referee; the main request should be a robustness scan over the fixed background components, plus code release. I would cite it for the branching-ratio tables and the single-channel comparison, and I'd bring it to reading group to discuss the background-systematics issue.","headline":"Model-specific branching ratios and combined INTEGRAL/AMS-02 limits make this a useful paper, but the AMS-02 constraints hinge on a fixed pulsar/diffusion model; the scalar DM limits in particular are softer than the abstract suggests.","tokens_in":23289,"tokens_out":3960,"would_cite":true,"duration_ms":35462,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":["95.35.+d"],"model":"deepseek-v4-flash","headline":"The paper finds no evidence for dark photon or scalar dark matter decay and sets lower bounds on the decay lifetime of $10^{25}$ seconds at MeV masses and up to $10^{29}$ seconds near 10 GeV.","keywords":["dark photon","scalar dark matter","dark matter decay","indirect detection","INTEGRAL/SPI x-ray data","AMS-02 positron data","kinetic mixing","mass-proportional couplings"],"falsifier":"A concrete test would be to search the public AMS-02 positron spectrum for the sharp excess at $E = m_{A'}/2$ that dark photon decay into electron-positron pairs would imprint; seeing that feature with the predicted dark matter spatial morphology, or instead establishing from pulsar surveys that the assumed pulsar contribution is wrong by an order of magnitude, would settle the central claim.","tokens_in":22281,"feed_emoji":"🔭","tokens_out":13280,"duration_ms":115605,"temperature":0.7,"pith_summary":"The paper aims to establish that two well-motivated bosonic dark matter candidates—a dark photon coupled by kinetic mixing and a scalar mixed with the Standard Model Higgs—do not decay fast enough to leave any detectable signal in existing x-ray and cosmic-ray positron data. Working across 1 MeV to 2 TeV, the authors calculate the complete mass-dependent branching ratios for each model and search for the resulting photons and positrons in INTEGRAL/SPI and AMS-02 observations. They find no excess above the astrophysical background and translate that null result into lower limits on the dark matter lifetime: $10^{25}$ s for MeV-scale dark matter and up to $10^{29}$ s near 10 GeV. The result matters because it moves decay searches from toy single-channel final states to the multi-channel spectra that realistic models actually predict, and it sets coupling limits orders of magnitude stronger than the age of the Universe.","feed_headline":"No dark matter decay found; lifetimes must exceed 10^29 s","feed_subtitle":"MeV-scale dark photon or scalar dark matter must decay slower than 10^25 s; near 10 GeV, slower than 10^29 s.","key_machinery":"The load-bearing object is the complete decay table of the two portals as a function of dark matter mass: for the dark photon, kinetic mixing with the Standard Model neutral gauge bosons fixes partial widths to all fermion pairs and, above threshold, to $W$ pairs; for the scalar, Higgs mixing gives mass-proportional fermion couplings plus $W$ and $Z$ pair channels. These branching ratios determine the photon and positron spectra per decay, combined with final-state radiation for the low-energy x-ray search and electroweak- and QCD-corrected injection spectra for the high-energy positron search. The constraints come from template fits: a Monte Carlo fit of the dark matter spectrum on top of a modelled INTEGRAL/SPI x-ray background, and a refit of an AMS-02 positron background in which diffusion and pulsar parameters float while dark matter templates are added. A standard Galactic dark matter density profile provides the factor that converts a computed flux into a lifetime.","core_discovery":"In its own terms, the paper's central claim is that dark photon and scalar dark matter, with the standard kinetic-mixing and Higgs-mixing couplings, are ruled out as decaying dark matter for lifetimes below the quoted bounds across 1 MeV to 2 TeV. Using a 16-year INTEGRAL/SPI x-ray analysis for masses below 10 GeV, the authors constrain the lifetime to $10^{22}$–$10^{25}$ s for the dark photon and $10^{21}$–$10^{25}$ s for the scalar; using AMS-02 positrons from 10 GeV to 2 TeV, they reach about $10^{29}$ s near 10 GeV for the dark photon and $10^{26}$–$10^{27}$ s for the scalar. These numbers translate into kinetic-mixing limits of $10^{-26}$–$10^{-27}$ and scalar mixing-angle limits of $10^{-24}$–$10^{-27}$ in the GeV-to-TeV range, several orders of magnitude below what the age of the Universe alone demands. The paper further claims that reducing either model to a single decay channel, such as electron-positron or bottom-antibottom pairs, changes the derived constraints by up to three or four orders of magnitude, so the multi-channel treatment is essential for translating data into model parameters.","pith_inferences":["The same template-fitting approach could be applied to other decaying dark matter candidates with vector or scalar portals simply by replacing the branching ratios, so the quoted limits serve as reusable benchmarks for dark sector model building.","A future precise determination of the pulsar population from TeV halos or pulsar surveys would either tighten the AMS-02 limits or reveal systematic shifts of comparable size, because the pulsar background parameters are currently left free in the fit.","Combining the positron channel with neutrino or antiproton searches in a single multi-messenger fit would break the degeneracy between pulsar and dark matter components more sharply than positrons alone.","A future MeV-scale telescope covering the gap between roughly 10 MeV and 10 GeV could strengthen the x-ray limits by an order of magnitude or more once prompt hadronic photon production is computed, potentially closing the current sensitivity dip around the pion mass."],"forward_implications":["If the dark photon is the dark matter, kinetic mixing above about $10^{-26}$–$10^{-27}$ in the 10 GeV to 2 TeV range is excluded, so surviving models must have still smaller mixing or masses above 2 TeV.","For scalar dark matter, the opening of $W$ and $Z$ channels above 161 GeV produces a sudden jump in sensitivity, meaning high-mass scalar constraints are really probing the gauge-boson portal, not fermion final states.","Single-channel approximations used in past decay searches can misestimate the true lifetime bound by up to three or four orders of magnitude, so future constraints should be quoted for complete, mass-dependent branching ratios.","The data already require these dark matter candidates to be stable for 4–12 orders of magnitude longer than the age of the Universe, sharpening the target for future MeV-scale and cosmic-ray instruments.","The strong x-ray constraints below 10 GeV rely on final-state radiation, so improved modelling of prompt photon production from hadronization would make the INTEGRAL limits stronger where they are currently conservative."],"supporting_citations":[{"why":"The AMS-02 positron flux measurement that anchors all GeV-to-TeV constraints.","marker":"[112]"},{"why":"The combined secondary-plus-pulsar positron background model that dark matter templates are added to and re-fitted against AMS-02 data.","marker":"[116]"},{"why":"The 16-year INTEGRAL/SPI x-ray dataset and astrophysical background template used for the sub-10 GeV likelihood fits.","marker":"[95]"},{"why":"The low-mass decay package used to compute x-ray spectra from dark matter decay below 1.5 GeV.","marker":"[78]"},{"why":"The package providing electroweak- and QCD-corrected positron injection spectra for dark matter masses above 10 GeV.","marker":"[81]"},{"why":"The scalar dark matter model with Higgs mixing and mass-proportional couplings that fixes the scalar branching ratios.","marker":"[25]"},{"why":"The dark photon kinetic-mixing model and fermionic decay widths that fix the vector branching ratios.","marker":"[26]"},{"why":"The meson form factors used in the hadronic decay width of the dark photon to pions and kaons.","marker":"[64]"},{"why":"The final-state radiation formula used for x-ray constraints in the 1.5–10 GeV range.","marker":"[7]"}],"fun_headline_variants":["Dark photon, scalar DM decays excluded to 10^29 s","Dark matter decay ruled out: lifetimes > 10^29 s","INTEGRAL & AMS-02: dark matter decay lifetimes > 10^29 s","No dark photon or scalar decay: limits reach 10^29 s","New bounds: dark matter decays slower than 10^29 s"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The load-bearing assumption is that the pulsar-plus-secondary positron background used in the AMS-02 fit is the true astrophysical flux; if the real pulsar population has a different spectrum or spatial distribution, the quoted lifetime limits could move by orders of magnitude.","fun_headline_variants_meta":{"raw":{"variants":["Dark photon, scalar DM decays excluded to 10^29 s","Dark matter decay ruled out: lifetimes > 10^29 s","INTEGRAL & AMS-02: dark matter decay lifetimes > 10^29 s","No dark photon or scalar decay: limits reach 10^29 s","New bounds: dark matter decays slower than 10^29 s"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.00073,"raw_usage":{"total_tokens":3265,"prompt_tokens":940,"completion_tokens":2325,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":556,"completion_tokens_details":{"reasoning_tokens":2227}},"tokens_in":556,"tokens_out":2325,"duration_ms":13722,"temperature":1.0,"reasoning_tokens":2227,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-12T05:37:56.770541+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A concrete test would be to search the public AMS-02 positron spectrum for the sharp excess at $E = m_{A'}/2$ that dark photon decay into electron-positron pairs would imprint; seeing that feature with the predicted dark matter spatial morphology, or instead establishing from pulsar surveys that the assumed pulsar contribution is wrong by an order of magnitude, would settle the central claim.","supporting_citations":[],"review_version":1}