{"id":"10fe0d44-8287-4551-a6e2-cfe66072320d","arxiv_id":"2505.06365","paper_version":2,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"A displaced-vertex search for slepton pair production at the HL-LHC can probe RPV coupling lambda-prime-111 down to about 1e-7 and neutralino masses up to roughly 1 TeV, far beyond single-slepton production.","lead":"This paper simulates how the future high-luminosity LHC could detect pairs of long-lived supersymmetric particles, called neutralinos, that decay a few centimeters inside the detector. The proposed search could squeeze the allowed value of the RPV coupling lambda-prime-111 about a thousand times smaller than previous single-production searches.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The N=3 sensitivity contours assume zero DV background at 3000 fb^-1; scaling the ATLAS 0.02 background events from 32.8 fb^-1 yields ~1.8 expected events, which raises the 95% CL threshold and shrinks the claimed lambda' reach.","rationale":"The paper's central physics point is sound: pair production via electroweak couplings removes the lambda'^2 suppression in production, so the sensitivity to small lambda' is genuinely improved relative to single-slepton production. The overall direction of the result is robust. However, the quantitative headline — 'up to three orders of magnitude smaller' — is set by the outermost N=3 contour, and that contour is computed under a zero-background assumption that is directly contradicted by a conservative luminosity scaling of the ATLAS background quoted in footnote 6. Because this is the boundary that defines the claimed reach, and because the authors themselves flag the assumption as an extrapolation, the central quantitative claim is conditional on an unvalidated background model. I do not see an internal inconsistency in the physics; the issue is the absolute normalization of the projected reach. The reader's weakest_assumption identifies the same concern, so I agree with the conditional verdict. The suggested numerical recomputation with b=1.8 would settle whether the advertised improvement factor survives.","tokens_in":16343,"tokens_out":18170,"duration_ms":173258,"concrete_test":"Recompute the 95% CL exclusion contours in Figs. 5 and 6 using a Poisson/CLs treatment with b=1.8 expected background events at 3000 fb^-1 (scaled from the ATLAS 0.02 events at 32.8 fb^-1) and compare the resulting boundaries to the N=3 contours. If the minimum lambda' at any neutralino mass increases by more than 30%, or the maximum neutralino mass at fixed lambda' falls by more than 10%, the quantitative reach claimed in the abstract is not supported by the current analysis. As a control, repeat with b=0 to verify the procedure reproduces the published contours.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The load-bearing assumption is the zero-background signal region used for the 95% CL contours in Figs. 5 and 6. Footnote 6 reports ~0.02 background events in the ATLAS DV search [68] at 32.8 fb^-1 and then assumes zero background at 3000 fb^-1. A linear luminosity scaling gives ~1.8 expected background events. For a Poisson counting experiment with b=1.8 and the median observed count, the expected 95% CL exclusion requires about N~5 signal events rather than N=3; the lower boundary of the sensitivity region scales roughly as sqrt(N_threshold), so the minimum lambda' rises by ~25-30% and the maximum neutralino mass at fixed lambda' decreases. The abstract's specific claim of probing lambda' values 'up to three orders of magnitude smaller' than single-slepton production is therefore tied to the zero-background extrapolation. The paper acknowledges this limitation in footnotes 6 and 7, but the headline quantitative statement is not robust to a realistic background estimate. A related but secondary assumption is that ATLAS 13 TeV DV reconstruction efficiencies apply unchanged at HL-LHC pileup, which could further reduce the effective N.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper studies R-parity-violating supersymmetry with a light, long-lived bino-like neutralino LSP decaying via the coupling λ'_111 into an electron and two jets. Unlike an earlier single-slepton-production study, the neutralinos are produced via Drell-Yan-like pair production of left-handed selectrons, pp → e~+ e~- → e+ χ e- χ, so the production cross section is independent of λ' in the narrow-width limit. The authors simulate the signal at 13 TeV with MadGraph and Pythia, apply a displaced-vertex selection inspired by an ATLAS search, use parameterized ATLAS vertex efficiencies, and assume zero background at 3000 fb^-1 to derive 95% CL sensitivity contours in the (λ'_111, m_χ) and (m_χ, m_eL) planes. They find that the HL-LHC can probe λ'_111 down to about 10^-7 and neutralino masses up to about 1 TeV, claiming improvements of up to three orders of magnitude in λ' and four times in mass over the previously studied single-slepton production scenario.","tokens_in":16669,"tokens_out":9997,"duration_ms":106219,"significance":"The physical idea is clean and the paper is careful about many details: it provides a full cutflow, three benchmarks, a comparison with the 0νββ constraint, a CheckMATE recast of a prompt dilepton+MET search, and it displays contours for several values of the required signal-event number N, which allows the reader to gauge the impact of background or efficiency assumptions. The key claim—that pair production decouples the production rate from the RPV coupling and thereby extends the reach to much smaller λ'—is well motivated and likely correct in its qualitative form. If the detector performance assumptions hold, this is a valuable search strategy for a theoretically motivated scenario. The main caveats are the optimistic zero-background extrapolation and the assumption that Run-2 DV efficiencies carry over to HL-LHC pile-up, both of which are acknowledged in the text.","major_comments":[{"comment":"The 95% CL contours are drawn for N=3 signal events under the zero-background assumption at L=3000 fb^-1. The text reports about 0.02 background events at 32.8 fb^-1 in the ATLAS search [68]; a linear luminosity scaling gives about 1.8 expected background events at the HL-LHC. For a Poisson counting experiment with b=1.8, the expected 95% CL exclusion requires roughly N≈5 signal events, not 3. Since the lower boundary of the sensitivity region scales approximately as sqrt(N_threshold), the minimum λ'_111 rises by about 25–30% and the maximum neutralino mass at fixed λ' decreases. The abstract's headline claim of probing λ' values 'up to three orders of magnitude smaller' is therefore tied to this optimistic extrapolation. Please provide a quantitative estimate of the sensitivity with a realistic background (for example, using CLs or a b=1.8 benchmark) and adjust the abstract and conclusions accordingly, or explicitly state that the quoted numbers are for the zero-background idealization.","section":"Sec. 4.1, footnote 6"},{"comment":"The signal simulation forces each selectron to decay as e~L -> e ± χ~0_1, implicitly taking BR(e~L -> e χ) = 1. However, the RPV operator L Q D^c also contains the coupling of e~L to u and d quarks, so for λ'_111 ≳ 0.1 the direct RPV decay e~L -> u dbar can compete with the electroweak decay and reduce the signal yield in the upper part of Fig. 5. Please quantify this branching-ratio suppression and either include it in the simulation or restrict the sensitivity plots to the region where it is negligible.","section":"Sec. 3 and Eq. (2.2)"},{"comment":"The analysis assumes that the ATLAS 13 TeV displaced-vertex reconstruction efficiencies from Ref. [68] remain unchanged at the HL-LHC pile-up of about 200 interactions per crossing. Since the signal yield is directly proportional to these efficiencies, a degradation of even 20–30% would shift the exclusion boundaries noticeably. Please discuss the expected pile-up dependence and show, for instance, the sensitivity contours for reduced efficiencies (e.g., 50% of the nominal efficiency); the higher-N contours in Fig. 5 give a partial handle, but an explicit statement would make the robustness of the reach clearer.","section":"Sec. 3, footnote 6"}],"minor_comments":[{"comment":"The word 'accesible' is a typo and should be 'accessible'.","section":"Abstract"},{"comment":"The axis labels show corrupted exponents such as '10□7' and '10□4'; these should be rendered as 10^{-7} and 10^{-4}.","section":"Figs. 5 and 6"},{"comment":"The signal is simulated at √s=13 TeV, but the HL-LHC operates at 14 TeV; the paper does not state how the production cross section is scaled to 14 TeV. Please comment on the expected increase (typically 10–20% for these masses) or justify neglecting it.","section":"Sec. 3"},{"comment":"The decay-width relation is written as a proportionality; giving the explicit expression with the phase-space factor and color factor would make the scaling clearer.","section":"Eq. (2.4)"},{"comment":"The claim that mass splittings as low as 4 GeV can be probed relies on displaced electrons passing the pT>25 GeV trigger; please clarify whether the default generator cut of pT>10 GeV (footnote 5) applies to all final-state electrons and how the single-electron trigger efficiency is modeled for displaced electrons.","section":"Sec. 4.1"},{"comment":"The CheckMATE recast of the ATLAS dilepton+MET search is described as being performed at √s=14 TeV, while the main signal samples are generated at 13 TeV; please clarify whether the recast uses separate 14 TeV event generation or rescales the 13 TeV samples.","section":"Appendix A"}],"recommendation":"major_revision","confidential_remarks":"The paper is within the scope of JHEP and the central physics idea is sound. The main risk is overstating the sensitivity given the zero-background and unchanged-efficiency assumptions; the authors already provide higher-N contours, so a revision that quantifies these effects should be straightforward. I do not see any concern about novelty or attribution."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Dear colleague,\n\nThis paper is a clean phenomenological projection for long-lived neutralinos in RPV SUSY, produced via electroweak pair production of sleptons and decaying via lambda-prime-111. The genuinely new piece is the decoupling of production from the RPV coupling: the pair-production cross section is independent of lambda-prime, so sensitivity to the coupling enters only through the neutralino decay. Applying the authors' earlier DV search strategy to this channel, they claim the HL-LHC can probe lambda-prime-111 down to about 1e-7 and neutralino masses up to about 1 TeV, roughly three orders of magnitude better in the coupling than their single-slepton study. That direction is well motivated, and the Monte Carlo work is standard and clearly presented.\n\nWhat I like: the cutflows are explicit, the efficiencies are shown as functions of mass and c-tau, and the paper includes a CheckMATE recast of a prompt dilepton+MET search for complementarity. The comparison with the single-production case is direct, so the claimed improvement is easy to verify. There is no circularity: the production is electroweak and the decay width relation is standard RPV physics.\n\nThe soft spots are in the quantitative reach. The N=3 contours are drawn under a zero-background assumption, extrapolated from about 0.02 events at 32.8 fb^-1 in the ATLAS DV search. Scaling to 3000 fb^-1 gives about 1.8 expected background events, which would shift the 95% CL threshold to N~5 and shrink the reach in both lambda-prime and neutralino mass. That is a real limitation, and the abstract's headline number is tied to it. To their credit, the paper is transparent about this in footnotes 6 and 7, and figure 5 shows contours for several higher N values, so a reader can see how the reach degrades. Still, the central quantitative claim should be stated with the background caveat attached. Also minor: signal cross sections are at 13 TeV while the projection is nominally HL-LHC at 14 TeV, and the ATLAS 13 TeV DV efficiencies are assumed to carry over to HL-LHC pileup. Both are common in this literature and unlikely to change the qualitative conclusion.\n\nBottom line: the paper is a solid, honest projection, and the production/decay decoupling is a useful idea. It is not a discovery paper, but it deserves a serious referee. I would send it to review and engage with it, asking the authors to propagate the zero-background caveat into the abstract and to show the N=5 contours (or quote values with b=1.8).","headline":"Solid, honest projection: the pair-production/decay decoupling gives a real and interesting gain for RPV neutralino searches, but the headline reach is pinned to a zero-background extrapolation that should be caveated.","tokens_in":17167,"tokens_out":2784,"would_cite":true,"duration_ms":26566,"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":"Pair production of sleptons separates the RPV coupling from the production rate, letting the HL-LHC reach couplings near 10^-7 and neutralino masses about four times the single-slepton channel.","keywords":["R-parity violation","long-lived particles","displaced vertices","supersymmetry","light neutralino","slepton pair production","HL-LHC","electroweak production"],"falsifier":"Run the same displaced-vertex selection ($|d_0|>2$ mm, 4 mm $2$ mm, transverse decay radius 4-300 mm, longitudinal position $|z_{\\rm DV}|<300$ mm, $n_{\\rm trk}\\ge 5$, $m_{\\rm DV}\\ge 10$ GeV) and the parameterized vertex-level efficiencies in the $m_{\\rm DV}$ versus $n_{\\rm trk}$ plane.","core_discovery":"The paper's central claim is that the process $pp\\to \\tilde e_L^+ \\tilde e_L^- \\to e^+ \\tilde\\chi_1^0\\, e^- \\tilde\\chi_1^0$ can be used at the HL-LHC to search for long-lived bino-like neutralinos in the RPV-MSSM, and that this channel is much more sensitive than the single-slepton production channel $pp\\to \\tilde e_L \\to e \\tilde\\chi_1^0$. The slepton-pair production cross section, mediated by $Z/\\gamma^*$ exchange, is essentially independent of $\\lambda'_{111}$ as long as the coupling is small enough not to affect the slepton's total decay width, so the only coupling dependence enters through the neutralino decay width $\\Gamma_{\\tilde\\chi_1^0} \\propto m_{\\tilde\\chi_1^0}^5 (\\lambda'_{111}/m_{\\tilde e_L}^2)^2$. With a displaced-vertex selection requiring tracks with $|d_0|>2$ mm, $r_{\\rm DV}$ between 4 and 300 mm, $|z_{\\rm DV}|<300$ mm, at least five tracks, and $m_{\\rm DV}\\ge 10$ GeV, using parameterized vertex efficiencies from the reference displaced-vertex search, the analysis obtains 95% C.L. exclusion contours at 3000 fb$^{-1}$. For $m_{\\tilde e_L}=0.5$ TeV the reach spans $\\lambda'_{111}$ from about $10^{-7}$ to $10^{-1}$ and neutralino masses from 10 GeV up to near the selectron mass; for $\\lambda'_{111}=10^{-5}$, neutralino masses up to about 800 GeV and selectron masses up to about 1.25 TeV are probed. The paper also notes that the strategy applies equally to the related couplings $\\lambda'_{112}$, $\\lambda'_{121}$, and $\\lambda'_{122}$, because the jets are not flavor-tagged.","pith_inferences":["Combining this pair-production search with the single-slepton channel of the earlier study could cover the compressed region near $m_{\\tilde\\chi_1^0} \\approx m_{\\tilde e_L}$, where the pair-production signal weakens kinematically; the single-production rate, though suppressed by $\\lambda'_{111}$, is not cut off by that threshold.","The zero-background assumption is the main fragility: if the ~0.02 background events at 32.8 fb$^{-1}$ scale linearly with luminosity, the expected background at 3000 fb$^{-1}$ is about 1.8 events, enough to weaken the $N=3$ exclusion contours at the low-coupling boundary.","Dedicated displaced-electron triggers, beyond the 25-GeV single-electron trigger assumed here, could extend the reach to smaller mass splittings and longer lifetimes; the analysis already benefits from events triggered by displaced electrons coming from neutralino decays."],"forward_implications":["At 3000 fb$^{-1}$ and $m_{\\tilde e_L}=0.5$ TeV, the search would probe $\\lambda'_{111}$ between about $10^{-7}$ and $10^{-1}$, covering neutralino masses from 10 GeV up to about the selectron mass, including mass splittings as small as 4 GeV.","For $\\lambda'_{111}=10^{-5}$, the reach extends to neutralino masses up to about 800 GeV and selectron masses up to about 1.25 TeV; for $\\lambda'_{111}=10^{-4}$, neutralino masses of about 20-300 GeV with selectron masses between 0.25 and 1.25 TeV are accessible.","No sensitivity is found for $\\lambda'_{111} \\lesssim 10^{-8}$, marking a lower boundary on the coupling reach of this channel.","Because the two final-state jets are not flavor-tagged, the same displaced-vertex strategy is sensitive to the related couplings $\\lambda'_{112}$, $\\lambda'_{121}$, and $\\lambda'_{122}$.","The displaced-vertex search region is complementary to the prompt dilepton-plus-missing-energy search, which only excludes very long-lived neutralinos that escape as missing energy."],"supporting_citations":[{"why":"Supplies the single-slepton-production benchmark whose reach in $\\lambda'_{111}$ and neutralino mass this paper directly extends and compares against.","marker":"[32]"},{"why":"Supplies the displaced-vertex signal-region cuts, the parameterized vertex efficiencies in the $m_{\\rm DV}$ vs $n_{\\rm trk}$ plane, and the ~0.02 background-event estimate at 32.8 fb$^{-1}$ behind the zero-background assumption.","marker":"[68]"},{"why":"Provides the neutrinoless double-beta-decay constraint on $\\lambda'_{111}$ shown as a comparison curve that the proposed HL-LHC sensitivity exceeds.","marker":"[63]"},{"why":"Defines the prompt dilepton-plus-missing-energy search that is recast to set the complementary prompt-exclusion region in the mass planes.","marker":"[71]"}],"fun_headline_variants":["Slepton pairs extend HL-LHC reach for RPV neutralinos","Displaced vertices from slepton pairs improve neutralino search","Pair-produced sleptons probe 4x heavier RPV neutralinos at HL-LHC","Slepton pair channel accesses 1000x smaller RPV couplings","Long-lived neutralinos via slepton pairs: a sharper HL-LHC search"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The projected exclusions assume the displaced-vertex search region contains zero background events at the full high-luminosity dataset, extrapolated from about 0.02 background events in the smaller dataset that defined the signal region, and that the vertex-tagging efficiency is unchanged at higher pile-up.","fun_headline_variants_meta":{"raw":{"variants":["Slepton pairs extend HL-LHC reach for RPV neutralinos","Displaced vertices from slepton pairs improve neutralino search","Pair-produced sleptons probe 4x heavier RPV neutralinos at HL-LHC","Slepton pair channel accesses 1000x smaller RPV couplings","Long-lived neutralinos via slepton pairs: a sharper HL-LHC search"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000403,"raw_usage":{"total_tokens":2243,"prompt_tokens":1231,"completion_tokens":1012,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":847,"completion_tokens_details":{"reasoning_tokens":915}},"tokens_in":847,"tokens_out":1012,"duration_ms":10319,"temperature":1.0,"reasoning_tokens":915,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-15T22:44:59.827629+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Run the same displaced-vertex selection ($|d_0|>2$ mm, 4 mm $