{"id":"fb1440d1-8721-4fbc-b932-bec9fcacfead","arxiv_id":"2501.19322","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":1.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"A faithful review of the strongest current bounds on Lorentz violation, superheavy dark matter, cosmic strings, and sterile neutrinos from ultra-high-energy cosmic-ray, gamma-ray, and neutrino searches.","lead":"This proceedings review collects the constraints that ultra-high-energy cosmic rays, gamma rays, and neutrinos place on physics beyond the Standard Model. It surveys bounds on Lorentz invariance violation, superheavy dark matter, cosmic strings, and sterile neutrinos, mostly from the Pierre Auger Observatory, IceCube, and ANITA.","discovery_kind":"review","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The flagship eta_pi01 bound inherits its main uncertainty from air-shower simulations; if hadronic models mispredict muon-number fluctuations, the quoted limit could shift. A re-analysis with an alternate interaction model and data-driven composition would settle it.","rationale":"The paper is a proceedings review, and its central claim is that the cited analyses place the quoted BSM constraints. The weakest point in that chain is the air-shower simulation dependence of the LIV bounds, exactly as the reader identified. The 'optimal mixture' of primaries and the use of a specific hadronic interaction model are inherited from the Auger analysis [8]; the review does not (and need not) reproduce that analysis, but the headline constraint cannot be stronger than the simulation toolchain that produces it. The reader's CONDITIONAL verdict already accounts for this as a caveat, and the minor mechanical issues (Eq. 11 Planck-mass convention, garbled Fig. 5 axis, uncited LIGO/Virgo comparison) do not alter the substance. Thus the concern does not move the verdict, but it is worth stating explicitly and testing because the eta_pi01 limit is the paper's flagship number.","tokens_in":10619,"tokens_out":7774,"duration_ms":72367,"concrete_test":"Rerun the Section 2.1 exclusion: use the Auger muon-fluctuation data and the same eta_pi01 grid as [8], but switch the hadronic interaction model (e.g., EPOS-LHC to Sibyll 2.3d) and replace the fluctuation-maximizing proton/iron mixture with the composition inferred from Auger's measured <Xmax>. If the 90% CL lower limit on eta_pi01 shifts by more than about 50% (i.e., becomes weaker than -6e-6), the quoted bound is model/composition dependent and the review's central claim needs qualification.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The paper's flagship constraint, Eq. (2) eta_pi01 > -6e-6 (90% CL), is derived by comparing measured relative muon-number fluctuations (Fig. 1) to air-shower simulations for eta_pi01 in [-1e-3, -1e-15]. The comparison assumes (i) an 'optimal' proton/iron mixture brackets the true composition at each energy, and (ii) hadronic-interaction models reliably predict the relative fluctuation level at 1e17-1e19 eV. Neither assumption is defended in the text; both are inherited from [8]. If the true composition differs from the bracketing mixture, or if models mispredict the variance of muon number (a known concern given the muon puzzle), the 90% exclusion interval could shift. The analogous Xmax-based kappa bound (Eq. 6) carries the same model dependence, plus the caveat in footnote 2 that primaries must reach Earth without radiating. Because the paper asserts these as 'the constraints a BSM model must satisfy,' the load-bearing element is the validity of the simulation toolchain, not the internal logic of the review.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"This paper is the written version of a UHECR2024 proceedings talk. It reviews constraints on BSM physics obtained from ultra-high-energy cosmic-ray air showers and from ultra-high-energy gamma-ray and neutrino searches. The review covers: Lorentz invariance violation via the neutral-pion LIV coefficient eta_pi01 and the isotropic non-birefringent QED coefficient kappa; superheavy dark matter, especially gravitino dark matter with R-parity-violating decays; cosmic-string cusp emission of moduli and the associated neutrino fluxes; and upward-going air-shower searches, including the interpretation of the ANITA anomalous events and future sterile-neutrino sensitivity with POEMMA. No new calculations are presented; the paper compiles and restates published results, with the main constraints being Eq. (2) for eta_pi01, Eq. (6) for kappa, Eq. (14) for mu', Eq. (16) for G mu as a projected sensitivity, and the Auger upward-going flux limits in Section 6.","tokens_in":10760,"tokens_out":10765,"duration_ms":107107,"significance":"As a review, the paper is useful and appropriate for its venue: it anchors each constraint to a concrete model parameter, gives the relevant scaling relations and confidence levels, and names the original analyses. It also correctly distinguishes existing exclusion bounds (Eqs. 2, 6, 14, and the Auger upward-going limits) from future detection prospects (Eq. 16 and Fig. 6). The review is a convenient entry point for model builders who need current UHECR-based limits. Its limitations are largely those of the cited analyses rather than of the review's internal logic; in particular, the muon-fluctuation and Xmax constraints in Section 2 inherit the hadronic-interaction and composition assumptions of Refs. [8]-[10]. I do not regard this inheritance as an error in the manuscript, but an explicit caveat would improve the accuracy of the review for readers who use it as a constraints compendium.","major_comments":[],"minor_comments":[{"comment":"The sentence introducing Eq. (2) says the constraints were 'obtained in a robust way', but the 90% CL bound depends on the hadronic interaction models used in the air-shower simulations and on the assumption that the optimal proton/iron mixture brackets the true composition at each energy. Please add a sentence stating this model dependence explicitly and directing the reader to Ref. [8] for the treatment of these systematics.","section":"Section 2.1, Eq. (2)"},{"comment":"Eq. (11) evaluates to 2e8 GeV only if M_P is the reduced Planck mass, whereas Eq. (1) defines M_P as 'the Planck mass' without qualification. Please state the convention for M_P at first use; otherwise the numerical value in Eq. (11) is not reproducible as written.","section":"Section 4, Eq. (11)"},{"comment":"The sentence 'These limits are stringent enough to exclude a physics origin of the two anomalous ANITA events' is stronger than the preceding material supports. The quoted Auger upper limits are derived for an assumed isotropic flux with E^-1 or E^-2 spectra; beamed or transient sources are not excluded by those numbers. Please qualify the conclusion as excluding the corresponding isotropic, power-law flux interpretations rather than 'a physics origin' in general.","section":"Section 6"},{"comment":"The caveat that the primary must reach Earth without radiating is essential to the validity of the kappa bound in Eq. (6). Please move this caveat from the footnote into the main text so that it is not easily missed by readers.","section":"Section 2.2, footnote 2"},{"comment":"Eq. (16) appears as if it were an existing exclusion bound, while the text correctly states that it is a detection prospect ('would make it possible to probe'). Adding 'projected' or 'would be probed' to the equation or its surrounding sentence would prevent misreading.","section":"Section 5, Eq. (16)"}],"recommendation":"minor_revision","confidential_remarks":"To the editor: this is a proceedings review rather than an original research contribution, and I have evaluated it on that basis. The self-citations in Refs. [16] and [35] are directly relevant to the topics reviewed and are used as sources, not as self-promotion; I do not see a conflict requiring action. The stress-test concern about the air-shower simulation toolchain behind Eq. (2) is a legitimate caution for users of the constraints, but it does not undermine the review's purpose: the text explicitly attributes the derivation to Ref. [8]. My minor-revision recommendation is driven by the local clarity issues listed above, especially the M_P convention in Eq. (11) and the overstatement about ANITA in Section 6."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"You can skim this one quickly. It is a proceedings review for UHECR2024, and it makes no new claims—every bound comes from cited collaboration papers and theory works. That is not a criticism; that is the genre. What it does well is organize a set of important constraints into one place with clear statements of the limits and their confidence levels: the eta_pi01 > -6e-6 muon-fluctuation bound, the kappa interval from Xmax and photon decay, the superheavy gravitino parameter relations, the cosmic-string G mu reach, and the upward-going shower limits. The equations reproduce the published derivations, and the paper is honest about where assumptions enter, e.g. footnote 2 on primaries without radiating. The soft spots are minor but real. Equation (11) uses the reduced Planck mass without saying so—the quoted 2e8 GeV only works with M_P ~ 2.4e18 GeV. Figure 5 has a garbled x-axis and two limit curves that are not cited. The LIGO/Virgo comparison in Section 5 has no reference. None of these affect the substance, but they should be cleaned up before this goes into anyone's reading list. The deeper caveat is the one the stress test flagged: the flagship eta_pi01 bound depends on air-shower simulations predicting relative muon-number fluctuations, and the optimal proton/iron bracketing is a premise inherited from [8]. The review does not defend that premise, but it also does not hide it—the method is described in a few lines and the citation is there. If you plan to use these constraints in your own work, read the underlying Auger analysis, not just this summary. That is true for any review, and this one does not oversell. On the citation pattern: the self-citations (Refs. [16], [35]) are to the author's own work, but they are appropriately used as sources for specific model calculations, and the review is clearly framed as a survey by a collaboration member. No circularity problem. Who is this for? A graduate student or a theorist wanting a quick, reliable survey of what UHECR searches currently constrain. It is not a paper that changes anything, but it is a useful reference point. I would send it to a referee for a quick accuracy pass—these numbers get quoted, so the transcription should be checked. With the minor fixes, it is fine for proceedings publication.","headline":"A faithful, well-organized proceedings review of current UHECR-based BSM constraints; no new results, but a useful map with a few small editorial warts.","tokens_in":760,"tokens_out":1734,"would_cite":false,"duration_ms":35195,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"Ultra-high-energy cosmic-ray searches now place quantitative exclusion bounds on several beyond-Standard-Model parameters, from Lorentz-violating coefficients to gravitino dark-matter couplings and cosmic-string tension.","keywords":["ultra-high-energy cosmic rays","extensive air showers","Lorentz invariance violation","Standard Model Extension","superheavy dark matter","cosmic strings","sterile neutrinos","upward-going showers"],"falsifier":"Compare two hadronic-interaction models at $10^{19}$ eV: if the predicted relative muon-number fluctuation changes by as much as the difference between the excluded and allowed curves in Fig. 1, the $\\eta_{\\pi^0 1}$ bound would have to be re-derived. A direct check is a future measurement of muon-number fluctuations at the upgraded Auger observatory with an independently determined composition, which would either confirm the optimal proton/iron mixture or break the assumption behind bound (2).","tokens_in":16,"feed_emoji":"🌌","tokens_out":9919,"duration_ms":154529,"temperature":0.7,"pith_summary":"Ultra-high-energy cosmic rays are the only particles available for probing scales well above a few tens of TeV, and this review collects what their observed silence currently rules out. The paper argues that concrete beyond-Standard-Model setups—Lorentz invariance violation, superheavy dark matter, cosmic strings, and sterile neutrinos—can be tested through air-shower observables and diffuse gamma-ray and neutrino fluxes. Its central message is that existing data already fix quantitative exclusion ranges, such as $\\eta_{\\pi^0 1} > -6\\times 10^{-6}$ at 90% confidence and $-6\\times 10^{-21} < \\kappa < 3\\times 10^{-20}$ at 98% confidence, and that the upgraded Auger observatory will decide whether a sub-dominant proton component reopens the case for new physics at the highest energies. The reader should take the paper as the current map of what a viable BSM model must survive.","feed_headline":"Cosmic-ray data rule out part-per-million Lorentz violation","feed_subtitle":"Muon fluctuations, shower depth, and neutrino searches together yield the current BSM exclusion map.","key_machinery":"Extensive air showers act as the calorimeter that converts Lorentz violation into measurable changes: neutral pions that stay stable keep feeding hadronic sub-showers, which lowers the relative fluctuation of the muon number, while faster photon propagation or vacuum Cherenkov emission makes the shower maximum shallower. The second load-bearing mechanism is fragmentation: a superheavy particle decaying at high energy produces cascades of Standard Model particles whose prompt gamma-ray and neutrino fluxes are computed from QCD and electroweak fragmentation functions, and the absence of these fluxes above observed limits yields the dark-matter, cosmic-string, and sterile-neutrino constraints. For upward-going events, the rising Standard Model neutrino-nucleon cross section makes the Earth a filter, and any event emerging from below must be compared with the predicted small background from mis-reconstructed UHECR showers.","core_discovery":"Working within the Standard Model Extension, the paper establishes that air-shower measurements exclude negative values of the leading Lorentz-violating neutral-pion coefficient below $\\eta_{\\pi^0 1}\\simeq-6\\times10^{-6}$ at 90% CL, because such values suppress $\\pi^0$ decay and reduce the relative muon-number fluctuations below what Auger observes. The shower depth and the absence of vacuum Cherenkov radiation and photon decay constrain the isotropic CPT-even QED parameter to $-6\\times10^{-21}<\\kappa<3\\times10^{-20}$ at 98% CL. For decaying superheavy gravitino dark matter, requiring the associated gamma-ray and neutrino fluxes to stay below observed limits gives an R-parity-violating coupling bound $\\mu' \\lesssim 10^{-5}(M_{3/2}/10^8\\,\\mathrm{GeV})^{-2}\\,\\mathrm{GeV}$, and cosmic-string models with moduli emission become observable only for tensions $G\\mu \\lesssim 10^{-20}$. The Auger search for upward-going showers, with expected background $0.27\\pm0.12$ events, excludes a physics origin for the two ANITA anomalous events under $E^{-1}$ and $E^{-2}$ spectra. As a review, the paper's contribution is to state these exclusions as the current quantitative constraints that BSM models must pass.","pith_inferences":["The author leaves implicit that the muon-fluctuation observable could also bound Lorentz violation in the charged-pion or photon sector, since any shifted threshold that changes the hadronic-to-electromagnetic balance of the shower affects the same measured quantity.","A testable extension of the $\\kappa$ analysis would be to use the shower width in addition to $X_{\\mathrm{max}}$, because electromagnetic-subshower development leaves a wider fingerprint than a single depth value.","The cosmic-string prediction could be sharpened by fitting gamma-ray and neutrino limits jointly, since moduli decaying to gluons produce photons and neutrinos from the same quark-gluon cascade and the two channels are not independent.","The same Earth-emergence geometry that excludes the ANITA events can be reused to search for deca-GeV sterile neutrinos from a bright transient such as GRB 221009A, and the paper's sensitivity estimate for POEMMA indicates this would be competitive with long-lived-particle experiments."],"forward_implications":["Any BSM model that induces a negative $\\eta_{\\pi^0 1}$ below $-6\\times10^{-6}$ is excluded at 90% CL by the observed muon-content fluctuations.","If cosmic strings emit moduli that decay to gluons, the predicted neutrino flux has a sharp rise above the cosmogenic floor, so a detection at Auger or a next-generation detector would probe tensions down to $G\\mu\\simeq10^{-20}$.","R-parity-violating gravitino dark matter must satisfy $\\mu'\\lesssim10^{-5}(M_{3/2}/10^8\\,\\mathrm{GeV})^{-2}\\,\\mathrm{GeV}$ to keep the resulting ultra-high-energy gamma-ray and neutrino fluxes within current limits.","The Auger upward-going limits exclude a physics origin for the ANITA anomalous events under simple $E^{-1}$ and $E^{-2}$ spectra, so any BSM explanation must alter the spectral assumption or the propagation.","A future measurement of mass composition at the upgraded Auger observatory will determine whether the sub-dominant proton component required in some scenarios remains a viable place for BSM physics."],"supporting_citations":[{"why":"Supplies the Auger muon-content data and the simulation comparison from which the $\\eta_{\\pi^0 1}>-6\\times10^{-6}$ bound is derived.","marker":"[8]"},{"why":"Provides the bound on positive $\\kappa$ from the absence of vacuum Cherenkov radiation in ultra-high-energy air showers.","marker":"[9]"},{"why":"Provides the bound on negative $\\kappa$ from the non-observation of photon decay into a photon and a neutral pion.","marker":"[10]"},{"why":"Defines the EeV gravitino dark-matter scenario, including the relic-density constraint and the viable parameter space used for the decay-flux limits.","marker":"[31]"},{"why":"Gives the dominant R-parity-violating gravitino decay channels that set the gamma-ray and neutrino spectra entering the $\\mu'$ bound.","marker":"[32]"},{"why":"Supplies the cosmic-string moduli-emission model and the neutrino-flux calculation from cusp bursts used to derive the $G\\mu$ reach.","marker":"[34]"},{"why":"Reports the Auger upward-going shower search and the background estimate that exclude a physics origin for the ANITA events.","marker":"[37]"},{"why":"Presents the sterile-neutrino upscattering scenario and the POEMMA exposure calculation that defines the future sensitivity to deca-GeV neutral leptons.","marker":"[38]"}],"fun_headline_variants":["Air-showers rule out part-per-million Lorentz violation","UHECR searches bound dark matter and Lorentz symmetry","Cosmic rays set new BSM constraints from air showers","Gamma-ray and neutrino limits narrow BSM parameter space","Air-shower measurements exclude negative π0 Lorentz violation"],"cache_read_input_tokens":13440,"weakest_assumption_plain":"The bounds depend on the assumption that air-shower Monte Carlo simulations, together with an optimal proton/iron mixture at each energy, correctly predict the relative muon-number fluctuations and the depth of shower maximum at ultra-high energies; if the simulations mis-model hadronic interactions, the quoted Lorentz-violation limits would not follow.","fun_headline_variants_meta":{"raw":{"variants":["Air-showers rule out part-per-million Lorentz violation","UHECR searches bound dark matter and Lorentz symmetry","Cosmic rays set new BSM constraints from air showers","Gamma-ray and neutrino limits narrow BSM parameter space","Air-shower measurements exclude negative π0 Lorentz violation"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000333,"raw_usage":{"total_tokens":1837,"prompt_tokens":920,"completion_tokens":917,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":536,"completion_tokens_details":{"reasoning_tokens":840}},"tokens_in":536,"tokens_out":917,"duration_ms":9451,"temperature":1.0,"reasoning_tokens":840,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-09T20:36:26.975547+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Compare two hadronic-interaction models at $10^{19}$ eV: if the predicted relative muon-number fluctuation changes by as much as the difference between the excluded and allowed curves in Fig. 1, the $\\eta_{\\pi^0 1}$ bound would have to be re-derived. A direct check is a future measurement of muon-number fluctuations at the upgraded Auger observatory with an independently determined composition, which would either confirm the optimal proton/iron mixture or break the assumption behind bound (2).","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the Auger muon-content data and the simulation comparison from which the $\\eta_{\\pi^0 1}>-6\\times10^{-6}$ bound is derived."},{"cited_title":"13 Constraints on BSM physics Olivier Deligny","cited_arxiv_id":null,"evidence_quote":"Reports the Auger upward-going shower search and the background estimate that exclude a physics origin for the ANITA events."},{"cited_title":"Hunting for Neutral Leptons with Ultra-High-Energy Cosmic Rays","cited_arxiv_id":"2303.11352","evidence_quote":"Presents the sterile-neutrino upscattering scenario and the POEMMA exposure calculation that defines the future sensitivity to deca-GeV neutral leptons."}],"review_version":1}