{"id":"f553c0fa-a034-4078-812c-9c5aa4ae49f5","arxiv_id":"2607.26757","paper_version":1,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":4.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"Displaced heavy-neutrino signals in LRSM and U(1)B−L remain accessible at the HL-LHC, with parton-level mass, lifetime, and AFB handles in low-background regions.","lead":"Parton-level study of long-lived heavy neutrinos produced via W' (Left-Right Symmetric Model) and Z' (U(1)B−L) at the HL-LHC. It maps surviving parameter space and shows how displaced decays plus simple kinematics could tag mass, lifetime, and chirality.","discovery_kind":"extension","skeptic_critique":{"model":"grok-4.5","headline":"Characterization claim rests on unquantified parton-level yields and an untested background-free assertion for displaced same-sign dilepton+jets.","rationale":"The reader correctly isolated the weakest link: parton-level analysis plus an untested background-free claim cannot underwrite ‘neat’ extraction of mass, width and quantum numbers. My stress test only sharpens that point with the paper’s own rate and off-shell numbers (Tabs. I–III, Figs. 8–11) and supplies a single concrete Delphes-level check that would settle whether the characterization claim survives. No deeper internal inconsistency or parameter-space error was found; the BPs and handles remain useful. Therefore the CONDITIONAL verdict stands unchanged.","tokens_in":14627,"tokens_out":565,"duration_ms":32298,"concrete_test":"Process BP1 (and BP2) KS events through Delphes with a displaced-vertex module, applying published ATLAS/CMS displaced-lepton/jet efficiencies and isolation; count expected events inside the reconstructed W′ and N mass windows at 3000 fb^{-1} and recompute AFB with Poisson errors. If diagnostic bins contain ≲20–30 events or the AFB uncertainty erases the chirality asymmetry, the ‘neatly accessed’ claim fails at the stated strength.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim (Abstract; §§I, IV–V) that HL-LHC can ‘neatly’ extract N mass, width/lifetime and quantum numbers (plus W′/Z′ properties) via invariant masses, displacements and AFB relies on two linked conditions that the paper does not secure. First, the BPs (Tabs. I–III) give KS cross sections ∼6×10^{-4} pb; after the paper’s own SR1/SR2 split, charge channels, and the observation that off-shell W′ dominates and BP2 decays often leave the tracker (Figs. 8–11), the usable sample for mass peaks and especially AFB (Fig. 10) at 3 ab^{-1} is never shown to be statistically adequate. Second, the repeated assertion that displaced regions are ‘essentially free from SM backgrounds’ (Abstract, §V) is stated without any estimate of material interactions, heavy-flavor, cosmics or pile-up fakes. The parton-level distributions therefore do not demonstrate that the properties can be extracted; they only show that the shapes would be distinctive if backgrounds are negligible and statistics suffice. The paper itself flags the parton-level limitation (§I, Conclusions), so the load-bearing gap is precisely the missing bridge from those plots to a quantified characterization claim.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.5","summary":"The paper studies long-lived heavy neutrinos produced via extended gauge portals in the LRSM (W' → N ℓ) and a U(1)_{B−L} model (Z' → NN), with subsequent displaced same-sign dilepton + jets decays. Parameter space is scanned with SARAH/SPheno/MadGraph against published ATLAS/CMS cross-section limits (KS process, dilepton, diboson); three BPs per model are chosen with M(N) ~ 17–280 GeV, cτ ~ 0.04–0.5 cm and rates ~10^{-4} pb. Parton-level invariant-mass peaks, geometric displacements (modified DELPHES) and lepton AFB in the N rest frame are presented to argue that HL-LHC can extract N mass, width/lifetime and quantum numbers, and characterise the W'/Z' portals, because displaced regions are essentially free of SM backgrounds.","tokens_in":15072,"tokens_out":1115,"duration_ms":21240,"significance":"If the characterisation claim holds, the work supplies concrete, non-excluded BPs and a clear set of observables (on-/off-shell mass reconstructions, lab-frame displacements, chiral AFB) that experiments could use to move beyond mere discovery of displaced heavy neutrinos toward property extraction in two well-motivated gauge extensions. The simultaneous treatment of charged- and neutral-current portals, the explicit inclusion of interference where relevant, and the public BPs are useful for the LLP community. The result is a solid proof-of-concept rather than a full experimental projection; its lasting value is the identification of clean kinematic handles once backgrounds and detector effects are under control.","major_comments":[{"comment":"Abstract and §V claim that N mass, width and quantum numbers (and W'/Z' properties) can be ‘neatly accessed’ at HL-LHC. Tabs. I–III give KS rates ~6×10^{-4} pb; after the SR1/SR2 split of §IV.C, charge channels and the observation that off-shell W' dominates and BP2 often decays outside the tracker (Figs. 8–11), no event yields, efficiencies or statistical uncertainties at 3 ab^{-1} are shown. Consequently the AFB distributions (Fig. 10) and mass peaks are not demonstrated to be statistically usable. A minimal estimate of expected reconstructed events per BP/SR is required to support the characterisation claim.","section":"Abstract; §IV.C–D; Tabs. I–III; Figs. 8–11"},{"comment":"The repeated assertion that displaced same-sign dilepton+jets regions are ‘essentially free from SM backgrounds’ (Abstract, §V) is stated without any estimate of material interactions, heavy-flavour, cosmics or pile-up fakes. Because the entire characterisation argument rests on background-free shapes, even a rough order-of-magnitude assessment (or an explicit statement that none is attempted) is needed; otherwise the claim remains unquantified.","section":"Abstract; §V"},{"comment":"The analysis is purely partonic (§I, Conclusions). While acceptable for a first look, the invariant-mass and AFB observables used for mass and quantum-number extraction are sensitive to jet clustering, lepton isolation and tracker resolution once the N is boosted. The paper should either quantify how these effects smear the peaks/asymmetries or clearly downgrade the language from ‘neatly accessed’ to ‘kinematic handles that survive in a parton-level study’.","section":"§I; §IV.C–D; Conclusions"}],"minor_comments":[{"comment":"Fig. 3 caption and text refer to ‘observed cross section (see Ref. [29])’ but do not state whether the experimental limits already unfold acceptance; a one-sentence clarification would help the reader compare apples-to-apples.","section":"Fig. 3; §IV.A"},{"comment":"Notation switches freely between W' and W_R (and Z'/Z_{B−L}); a consistent choice after the first definition would improve readability.","section":"§II.A; §IV"},{"comment":"Several figures (e.g. 8–11, 13–14) lack explicit luminosity normalisation or unit labels on the vertical axes in the text description; adding them would make the plots self-contained.","section":"Figs. 8–14"},{"comment":"Typos: ‘ANAL YSIS’, ‘F eatures’, ‘RESUL TS’, ‘individuate’, and a few missing spaces around equation references.","section":"Throughout"}],"recommendation":"major_revision","confidential_remarks":"The manuscript is a competent but incremental phenomenology paper. The central gap is the leap from parton-level shapes to a characterisation claim; once the authors supply even rough HL-LHC yields and a background caveat, the paper becomes a useful reference for the LLP community. Scope is appropriate for a solid hep-ph journal."},"author_rebuttal":null,"desk_editor":{"model":"grok-4.5","letter":"The useful core here is a pair of updated parameter scans under recent ATLAS/CMS KS, dilepton and diboson limits, plus three explicit LLP BPs per model with tabulated rates, cτ and parton-level shapes (invariant masses, displacements, AFB). That is new relative to the cited LLP papers [20–24] and is done cleanly with the usual SARAH/SPheno/MadGraph pipeline.\n\nWhat they do well: they keep the BPs inside the still-allowed regions, show that off-shell W′ already matters at ~5 TeV, split SR1/SR2 accordingly, and demonstrate that AFB can in principle tag the chiral structure of the W′ while vanishing for the vector-like Z′. The displacement distributions are sensible and the self-citation is modest. Circularity is low; nothing is reverse-engineered to invent a signal.\n\nThe soft spot is exactly the one the stress-test flags, and it is load-bearing for the abstract’s claim. Cross sections sit at ~6×10^{-4} pb; after charge channels, SR splits and the fact that BP2 often leaves the tracker, the usable HL-LHC sample for mass peaks and especially AFB is never shown to be adequate. The repeated assertion that displaced same-sign dilepton+jets is “essentially free from SM backgrounds” is stated without any estimate of material interactions, heavy-flavor, cosmics or pile-up fakes. The paper itself flags the parton-level limitation in the introduction and conclusions, so the gap is acknowledged rather than hidden, but the characterization language still over-reaches the plots.\n\nThis is for people already working on heavy-neutrino LLPs or gauge portals who want ready-to-use BPs and a quick look at which observables might carry quantum-number information. It is not a foundational result and does not reorganize the subfield. A serious editor should send it to referees; the scans and BPs are real enough to deserve a proper background and detector-level check rather than a desk reject. I would cite the BPs if I needed numbers in this corner, but I would not lean on the “neatly accessed” phrasing until the simulation gap is closed.","headline":"Solid incremental LLP benchmarks and AFB/displacement handles for LRSM and U(1)B−L, but the ‘neatly accessed’ claim outruns the parton-level evidence.","tokens_in":15601,"tokens_out":554,"would_cite":true,"duration_ms":10154,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.5","headline":"Displaced heavy-neutrino decays at the HL-LHC can reveal mass, lifetime and quantum numbers in two gauge extensions of the Standard Model.","keywords":["long-lived particles","heavy neutrinos","Left-Right Symmetric Model","U(1)B−L","displaced vertices","HL-LHC","Keung-Senjanovic process","forward-backward asymmetry"],"falsifier":"A full detector-level simulation of the three published benchmarks that either fails to reconstruct the claimed mass peaks and AFB asymmetries above background, or shows that the displaced same-sign dilepton-plus-jets sample is dominated by residual Standard Model processes.","tokens_in":15537,"feed_emoji":"⚛️","tokens_out":862,"duration_ms":15612,"temperature":0.7,"pith_summary":"Heavy neutrinos that live long enough to decay away from the collision point can leave clean signatures at the High-Luminosity LHC. The paper studies two well-motivated extensions of the Standard Model—the Left-Right Symmetric Model and a U(1)B−L gauge extension—in which new heavy gauge bosons act as portals that produce these neutrinos at usable rates. In regions of parameter space still allowed by existing searches, the neutrinos decay inside the ATLAS and CMS trackers, producing same-sign dileptons plus jets. Because the decays occur far from the interaction point, ordinary Standard Model backgrounds are strongly suppressed. The authors show, at parton level, that the resulting kinematic distributions and angular asymmetries can reconstruct the neutrino mass and lifetime and diagnose the chirality or vector nature of the new gauge couplings. Three benchmark points per model illustrate that the High-Luminosity upgrade should collect enough events for this characterisation.","feed_headline":"HL-LHC can weigh and time long-lived heavy neutrinos","feed_subtitle":"Displaced same-sign dileptons reveal mass, lifetime and gauge couplings in two Standard Model extensions","key_machinery":"The Keung–Senjanović process (W′ → Nℓ → ℓℓjj) in the Left-Right Symmetric Model and the analogous Z′ → NN → ℓℓjj process in U(1)B−L, combined with laboratory-frame displacement distributions and forward–backward lepton asymmetries measured in the heavy-neutrino rest frame.","core_discovery":"In non-excluded regions of the Left-Right Symmetric Model and the U(1)B−L model where heavy neutrinos are long-lived, High-Luminosity LHC displaced-vertex signals (same-sign dileptons plus jets) allow extraction of the heavy-neutrino mass, width/lifetime and quantum numbers, together with characterisation of the W′ or Z′ portal, because Standard Model backgrounds are strongly reduced away from the interaction point.","pith_inferences":["The same displaced-vertex strategy could be applied to other gauge portals that produce Majorana neutrinos with centimetre-scale lifetimes.","Once detector-level efficiencies are known, the AFB measurement may become a model-discrimination tool between left–right and B−L scenarios even with modest event counts.","If the off-shell W′ contribution is as large as claimed, existing prompt searches may have underestimated the total rate in the multi-TeV W′ region."],"forward_implications":["HL-LHC displaced-vertex analyses can target both LRSM and U(1)B−L heavy neutrinos with the same final-state topology.","Invariant-mass peaks of lepton–jet systems can measure the heavy-neutrino mass even when the parent W′ or Z′ is off-shell.","Forward–backward asymmetries of the secondary leptons can distinguish right-handed W′ couplings from vector-like Z′ couplings.","Laboratory-frame displacement spectra directly constrain the proper lifetime (and hence the mixing or Yukawa couplings) of the heavy neutrino.","The three benchmark points per model supply concrete targets for dedicated ATLAS/CMS long-lived-particle searches."],"fun_headline_variants":["HL-LHC extracts mass and lifetime of long-lived heavy neutrinos","Displaced decays reveal heavy neutrino properties at HL-LHC","Long-lived heavy neutrinos characterised via displaced vertices","HL-LHC accesses heavy neutrino mass, width and quantum numbers","Same-sign dileptons expose W' or Z' portals to heavy neutrinos"],"cache_read_input_tokens":128,"weakest_assumption_plain":"A parton-level study without showering, hadronisation or full detector simulation is enough to claim that mass, width and quantum numbers can be cleanly extracted once the decays are displaced.","fun_headline_variants_meta":{"raw":{"variants":["HL-LHC extracts mass and lifetime of long-lived heavy neutrinos","Displaced decays reveal heavy neutrino properties at HL-LHC","Long-lived heavy neutrinos characterised via displaced vertices","HL-LHC accesses heavy neutrino mass, width and quantum numbers","Same-sign dileptons expose W' or Z' portals to heavy neutrinos"]},"model":"grok-4.5","effort":"low","cost_usd":0.002854,"raw_usage":{"total_tokens":946,"prompt_tokens":651,"num_sources_used":0,"completion_tokens":92,"cost_in_usd_ticks":28544000,"prompt_tokens_details":{"text_tokens":651,"audio_tokens":0,"image_tokens":0,"cached_tokens":128},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":203,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":651,"tokens_out":92,"duration_ms":4382,"temperature":1.0,"reasoning_tokens":203,"cache_read_input_tokens":128,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-30T21:59:30.724848+00:00","model_set":{"reader":"grok-4.5"},"falsifier":"A full detector-level simulation of the three published benchmarks that either fails to reconstruct the claimed mass peaks and AFB asymmetries above background, or shows that the displaced same-sign dilepton-plus-jets sample is dominated by residual Standard Model processes.","supporting_citations":[],"review_version":1}