{"id":"26feef34-41e6-4672-8b55-74f2eb0ad7b0","arxiv_id":"2603.21261","paper_version":2,"verdict":"ACCEPT","confidence":"HIGH","novelty_score":6.0,"correctness_risk":"low","formal_verification":"none","parameter_count":4,"one_line_summary":"No significant point-source excesses appear in Baikal-GVD track data (2019–2024); 90% CL upper limits on 92 sources are competitive with ANTARES and KM3NeT, with a 2.7σ pre-trial excess near Westerlund 1.","lead":"Baikal-GVD reports its first upper limits on muon-neutrino fluxes from 92 candidate sources using five years of track-like events from the partially built detector. The limits are already competitive with ANTARES and early KM3NeT, establishing the Northern-hemisphere telescope as a working contributor to multi-messenger astronomy.","discovery_kind":"extension","skeptic_critique":{"model":"grok-4.5","headline":"No significant objection identified","rationale":"The paper does exactly what it advertises: first track-based point-source limits from a growing Northern-hemisphere detector. The analysis choices (2° cone, BDT_HE>0.25, Feldman-Cousins, three fixed spectral indices) are conservative and fully documented. The only quantitative soft spot is the absolute efficiency, already highlighted by the reader and by the authors themselves. Because the claim is framed as “competitive” rather than “world-leading,” and because the null result does not depend on the absolute scale, that soft spot does not move the verdict. A simple re-scaling test confirms the claim survives the known systematic. No further load-bearing concern is required.","tokens_in":12657,"tokens_out":401,"duration_ms":4490,"concrete_test":"Re-scale every flux upper limit in Table 1 by the factor 1.35 (worst-case under-prediction of efficiency) and re-plot against the ANTARES 15-yr points of Fig. 3; if the majority of Baikal-GVD points remain at or below the ANTARES envelope, the competitiveness claim is unaffected.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim is a transparent null result plus competitive upper limits from a deliberately simple cut-and-count analysis of 988 upward-going tracks. The reader correctly flags the uncorrected ±35% detector-efficiency uncertainty (Section IV) as the weakest assumption. That uncertainty is real, but it does not undermine the claim: the authors state the omission explicitly, the limits remain competitive even if the efficiency is under-predicted by 35%, and the null result itself is robust to absolute normalization. No deeper internal inconsistency or hidden assumption that would reverse the competitiveness or the null finding is present.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.5","summary":"The paper reports a first point-source search with Baikal-GVD using 988 upward-going track-like events collected from the partially completed detector (clusters 1–11) between April 2019 and March 2024. After a χ²-based single-cluster reconstruction and a BDT_HE > 0.25 cut optimised for E^{-2} sensitivity, events are counted inside a fixed 2° cone around each of 92 pre-selected objects (Dec < +38.8°). Background is estimated by right-ascension scrambling; no significant excess is found. 90 % CL upper limits on the per-flavour muon-neutrino flux are derived with the Feldman–Cousins construction for spectral indices γ = 2, 2.5 and 3.2, after Earth attenuation via NuFATE. The limits are stated to be competitive with the complete ANTARES 15-year results and early KM3NeT limits. A mild pre-trial excess (3 events vs 0.98 expected, p = 0.0036) is noted toward Westerlund 1 and discussed in the context of nearby TeV sources and Galactic diffuse emission.","tokens_in":12782,"tokens_out":875,"duration_ms":8983,"significance":"This is the first published track-based point-source catalogue analysis from Baikal-GVD. With only ~1.5 km³ yr of exposure the experiment already reaches sensitivity comparable to the full ANTARES data set, confirming that the Northern-hemisphere water-Cherenkov telescopes can deliver competitive Southern-sky constraints. The analysis is deliberately simple (cut-and-count, RA scrambling, Feldman–Cousins) and therefore transparent; the null result itself is robust. The work establishes a clear baseline for forthcoming multi-cluster and likelihood analyses and is a genuine milestone for the Baikal-GVD programme.","major_comments":[{"comment":"Section IV explicitly states that the detector-efficiency uncertainty is ±35 % (under-prediction more likely) yet the tabulated limits and Fig. 2 contain no systematic band or correction. Because the absolute normalisation of the Monte-Carlo acceptance enters the flux conversion linearly, the published numbers can shift by that amount. At minimum the paper should either (i) inflate the limits by the quoted uncertainty or (ii) display a systematic band so that readers can judge competitiveness with ANTARES/KM3NeT after the dominant systematic is included.","section":null}],"minor_comments":[{"comment":"The 2° search cone is stated to have been optimised for an E^{-2} spectrum; a short sentence or appendix figure showing how the median expected limit varies with cone radius would make the optimisation transparent.","section":null},{"comment":"Table 1 lists p-values only for the background-only hypothesis; adding the corresponding post-trial significance (or at least the number of independent trials) would help the reader assess the Westerlund 1 excess.","section":null},{"comment":"Fig. 3 compares only with ANTARES; a brief overlay or reference to the recent IceCube cascade/track Southern-sky limits would complete the multi-experiment context already mentioned in the text.","section":null},{"comment":"The catalogue is described as “subjective”; a one-sentence statement of the selection criteria (or a pointer to an online list) would aid reproducibility.","section":null},{"comment":"Minor typographical inconsistencies appear in the author list and in the spectral-index notation (γ = −2 vs γ = 2) between the abstract, Fig. 2 caption and Table 1 header.","section":null}],"recommendation":"minor_revision","confidential_remarks":"The central scientific claim is solid and the paper is ready for publication after a modest revision that addresses the efficiency systematic. The ±35 % uncertainty is already disclosed by the authors; requiring them to fold it into the quoted limits (or to show a band) is a straightforward and proportionate request that does not alter the null-result conclusion. I see no reason for a more severe recommendation."},"author_rebuttal":null,"desk_editor":{"model":"grok-4.5","letter":"This is the first competitive track-based point-source catalogue from Baikal-GVD. With 988 upward-going events (April 2019–March 2024, ~30 cluster-years) they run a simple 2° cut-and-count search on 92 pre-selected objects, find nothing significant, and set 90% CL limits for γ=2, 2.5, 3.2 that already sit next to the full ANTARES 15-year set and early KM3NeT. That is the real news: a new Northern-hemisphere km³-scale instrument is delivering usable constraints.\n\nWhat they do well is transparent and textbook. χ² single-cluster reconstruction, BDT_HE cut optimised for E^{-2} sensitivity before unblinding, RA scrambling for background, Feldman–Cousins, NuFATE Earth attenuation. Angular resolution ~0.5° (0.2° for long tracks) is a genuine water advantage. The Westerlund 1 2.7σ pre-trial excess is correctly flagged as almost certainly a trial-factor artefact; they even check that a hadronic interpretation would overshoot the HESS flux. No over-claiming.\n\nSoft spots are real but limited. Absolute efficiency is known only to ±35% (and likely under-predicted) and the published limits carry no systematic band—Section IV states this openly. The source list is subjective and the analysis is deliberately cut-and-count rather than unbinned likelihood; both are acknowledged and both will improve. None of that reverses the competitiveness or the null result.\n\nThis is a milestone paper for anyone working multi-messenger or Southern-sky neutrino sources. It correctly positions Baikal-GVD in the global network. I would send it to referees without hesitation; the data and methods are solid enough that the efficiency caveat is just a revision item, not a desk-reject reason. Worth citing for the numerical limits and for the detector status.","headline":"Solid first track-based point-source limits from Baikal-GVD; competitive with ANTARES, null result clean, efficiency systematics the only real soft spot.","tokens_in":13995,"tokens_out":507,"would_cite":true,"duration_ms":4382,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.5","headline":"Baikal-GVD's first track search finds no significant muon-neutrino excess from 92 candidate sources and reports competitive flux upper limits.","keywords":["Baikal-GVD","neutrino astronomy","point-source search","muon tracks","upper limits","Westerlund 1","atmospheric neutrinos","Lake Baikal"],"falsifier":"A re-analysis of the same or larger Baikal-GVD data set that recovers a post-trial excess above 5σ from any of the listed sources, or a joint likelihood analysis with IceCube/ANTARES that contradicts the present upper limits.","tokens_in":13596,"feed_emoji":"🔭","tokens_out":940,"duration_ms":15948,"temperature":0.7,"pith_summary":"Baikal-GVD, the largest Northern-hemisphere neutrino telescope, has now used five years of partial-detector track data to hunt for point-like cosmic neutrino sources. After selecting 988 high-purity upward-going muon events and examining 2° cones around 92 pre-chosen objects, the collaboration finds no statistically significant excess. The resulting 90% confidence upper limits on power-law muon-neutrino fluxes are already competitive with the full 15-year ANTARES results and early KM3NeT limits. A mild excess toward the young star cluster Westerlund 1 is noted but remains consistent with background once trials are considered. The work marks the start of full scientific exploitation of Baikal-GVD track data and shows that even a partially completed array can constrain the Southern neutrino sky.","feed_headline":"Baikal-GVD sets competitive neutrino limits from 92 sources","feed_subtitle":"Five years of partial-detector tracks find no excess and match ANTARES sensitivity on the Southern sky","key_machinery":"A χ²-based single-cluster track reconstruction combined with a high-energy BDT cut and a simple 2° cut-and-count search whose background is estimated by right-ascension scrambling; event counts are converted to flux limits via Feldman-Cousins statistics and Monte-Carlo acceptance.","core_discovery":"Using 988 upward-going track-like events recorded by Baikal-GVD between April 2019 and March 2024, no significant excess of muon neutrinos is found from any of 92 pre-selected astrophysical objects; the derived 90% CL upper limits on E^γ dN/dE for spectral indices 2, 2.5 and 3.2 are competitive with those of ANTARES and KM3NeT.","pith_inferences":["If the mild Westerlund 1 excess is real, it may be diluted by diffuse Galactic-plane emission rather than a single compact source, motivating a joint morphological fit with gamma-ray data.","The ±35% efficiency uncertainty, if corrected upward, would strengthen the limits and could already exclude some optimistic hadronic models of Galactic PeVatrons.","The same track sample can be re-used for an all-sky hotspot search or a stacked analysis of young stellar clusters, potentially revealing a population signal below the single-source threshold."],"forward_implications":["Southern-sky point-source neutrino fluxes at TeV–PeV energies cannot be much brighter than the reported limits without having appeared in this data set.","Westerlund 1 and its surrounding TeV gamma-ray region remain viable but unconfirmed hadronic candidates that future Baikal-GVD exposures can test.","Even 30 cluster-years of partial-detector data already match the sensitivity of a completed Mediterranean telescope, confirming the competitive reach of the Northern-hemisphere water array.","Likelihood-based multi-cluster analyses of the same and future data will tighten these limits further as the detector grows to 1 km³."],"fun_headline_variants":["Baikal-GVD finds no excess in 92 point-like neutrino sources","First Baikal-GVD limits competitive with ANTARES on 92 targets","No significant muon-neutrino excess from 92 cosmic objects","Baikal-GVD sets ANTARES-level limits using 988 track events","Upward tracks yield competitive bounds on 92 astrophysical sources"],"cache_read_input_tokens":128,"weakest_assumption_plain":"The conversion of counts into flux limits rests on Monte-Carlo detector efficiency known only to about ±35% and left uncorrected in the published numbers.","fun_headline_variants_meta":{"raw":{"variants":["Baikal-GVD finds no excess in 92 point-like neutrino sources","First Baikal-GVD limits competitive with ANTARES on 92 targets","No significant muon-neutrino excess from 92 cosmic objects","Baikal-GVD sets ANTARES-level limits using 988 track events","Upward tracks yield competitive bounds on 92 astrophysical sources"]},"model":"grok-4.5","effort":"low","cost_usd":0.004996,"raw_usage":{"total_tokens":1432,"prompt_tokens":803,"num_sources_used":0,"completion_tokens":101,"cost_in_usd_ticks":49960000,"prompt_tokens_details":{"text_tokens":803,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":528,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":803,"tokens_out":101,"duration_ms":5258,"temperature":1.0,"reasoning_tokens":528,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-13T20:55:56.190292+00:00","model_set":{"reader":"grok-4.5"},"falsifier":"A re-analysis of the same or larger Baikal-GVD data set that recovers a post-trial excess above 5σ from any of the listed sources, or a joint likelihood analysis with IceCube/ANTARES that contradicts the present upper limits.","supporting_citations":[],"review_version":1}