# ============================================================================ # P06 — $U_1$ vector leptoquark $m_T$ recast in $pp \to \tau\nu$ (ATLAS+CMS) # ---------------------------------------------------------------------------- # Adapts ColliderAgent paper-reproduction prompt: # /home/shiqiu/ColliderAgent/paper-reproduction/1811.07920/prompt_figure_3.md # Source: arXiv:1811.07920 — vector leptoquark $U_1$ as resolution of # $R_{D^{(*)}}$ anomaly; recast of ATLAS + CMS $\tau\nu$ searches. # ============================================================================ id: P06 title: "Reproducing $U_1$ vector-leptoquark $\\sqrt{|g_c^* g_b|}$ vs $M_{U_1}$ exclusion from ATLAS+CMS $pp \\to \\tau\\nu$" arxiv_id: "1811.07920" venue: "ARC-Bench Physics 2026" paper_asset: null synthesis: | Reproducing the LHC sensitivity to a $U_1$ vector leptoquark from the $pp \to \tau\nu$ channel via $bc \to U_1 \to \tau\nu$ exchange, combining ATLAS + CMS searches in a binned profile-likelihood, as a benchmark of the agent's ability to (i) generate LQ events with bottom-quark and charm-quark initial-state partons, (ii) run two parallel detector-card simulations (Delphes ATLAS card vs CMS card), (iii) recast experimental data into a profile-likelihood fit. The Lagrangian couples $U_1$ to $(\bar c \gamma^\mu P_L \nu_\tau)$ and $(\bar b \gamma^\mu P_L \tau)$ with couplings $g_c, g_b$, and the diagnostic figure is the 2$\sigma$ exclusion contour in the $(\sqrt{|g_c^* g_b|}, M_{U_1})$ plane along with the LH and RH $R_{D^{(*)}}$ flavor-anomaly bands. A credible study (a) implements the $U_1$ Lagrangian (FeynRules .fr + UFO), (b) runs MadGraph + Pythia8 + Delphes for $M_{U_1} \in \{750, 1000, 1250, 1500, 2000, 2500, 3000, 4000, 5000\}$ GeV with both ATLAS and CMS cards (LHCO output), (c) applies the published ATLAS and CMS $\tau$-channel selections (lepton veto, hadronic-$\tau$ requirement, $E_T^\mathrm{miss}$ cut, $m_T$ cut), (d) builds a binned signal template that scales as $g^4$ and runs the per-bin profile likelihood with nuisance parameters $\theta_i$, (e) combines ATLAS + CMS, finds the 2$\sigma$ exclusion via $-2\Delta\ln\mathcal{L} = 4$, and (f) overlays the analytic LH band $g_\mathrm{LH}(M) = (M/v)\sqrt{2 V_{cb}\, \epsilon_L}$ with $\epsilon_L = 0.11 \pm 0.02$ and the analogous RH band. Research question: *does the agent reproduce the $(\sqrt{|g_c^* g_b|}, M_{U_1})$ exclusion contour and the $R_{D^{(*)}}$ overlay bands of Figure 3 of arXiv:1811.07920?* hypotheses: - id: H1 statement: "The combined ATLAS+CMS 2$\\sigma$ exclusion at $M_{U_1} = 1$ TeV gives $\\sqrt{|g_c^* g_b|} \\in [0.3, 1.5]$, matching the published value within 30%." measurable: true - id: H2 statement: "The reconstructed exclusion contour intersects the LH $R_{D^{(*)}}$ band ($\\epsilon_L = 0.11$) at an excluded mass $M_{U_1}^* \\in [1.0, 2.5]$ TeV." measurable: true - id: H3 statement: "Selection efficiency on signal events is $\\geq 5\\%$ at $M_{U_1}=1$ TeV in both ATLAS and CMS analyses (gauge of pipeline working end-to-end through Delphes)." measurable: true experiment_design: research_question: "Does the agent reproduce the 2$\\sigma$ exclusion contour for the $U_1$ vector leptoquark in the $(\\sqrt{|g_c^* g_b|}, M_{U_1})$ plane from combined ATLAS+CMS $pp \\to \\tau\\nu$ recast (Figure 3 of arXiv:1811.07920)?" conditions: - name: "atlas_recast" description: "Mass scan $M_{U_1} \\in \\{750, 1000, 1250, 1500, 2000, 2500, 3000, 4000, 5000\\}$ GeV at $\\sqrt{s}=13$ TeV, 10k events each, Pythia8 shower, Delphes ATLAS card, LHCO output. Selection: lepton veto, hadronic-$\\tau$ $p_T > 80$ GeV, $|\\eta_\\tau| < 2.3$, $E_T^\\mathrm{miss} > 150$ GeV, $m_T > 250$ GeV." - name: "cms_recast" description: "Same mass scan with Delphes CMS card; selection: lepton veto, $\\tau$ $p_T>80$ GeV, $|\\eta|<2.1$, $E_T^\\mathrm{miss}>200$ GeV, $0.7 < p_T^\\tau / E_T^\\mathrm{miss} < 1.3$, $\\Delta\\phi(\\tau, E_T^\\mathrm{miss}) > 2.4$, $m_T > 320$ GeV." baselines: - "Published ATLAS background table (22 bins, 250-3200 GeV log-spaced) and CMS background table (3 bins) act as the SM-only null hypothesis" metrics: - name: "exclusion_coupling_at_1tev" direction: "match_reference" description: "$\\sqrt{|g_c^* g_b|}$ at the 2$\\sigma$ exclusion boundary at $M_{U_1}=1$ TeV from combined fit." - name: "selection_efficiency" direction: "match_reference" description: "Fraction of generated signal events passing the ATLAS or CMS selection at $M_{U_1}=1$ TeV." - name: "rdstar_band_intersection_tev" direction: "match_reference" description: "Mass at which the LH $R_{D^{(*)}}$ band crosses the exclusion contour." datasets: - process_id: "pp_to_taunu_via_U1" sqrt_s_TeV: 13 description: "$pp \\to \\tau\\nu$ via $bc \\to U_1$ exchange. Two detector simulations (Delphes ATLAS, Delphes CMS)." compute_requirements: gpu_required: false estimated_wall_clock_sec: 3600 rubric_path: "experiments/arc_bench/config/physics/rubrics/P06.json" # --------------------------------------------------------------------------- # Agent-mode requirements (consumed by researchclaw.pipeline.requirements_judge # at stage 15 RESEARCH_DECISION). Schema mirrors B01.yaml: # id — stable identifier # type — advisory hint to the LLM judge (numeric | artifact | discussion) # description — natural-language statement of what must be true post-run # must_pass — true → unmet ⇒ rerun (1 retry max); false → optional # # The five generic must_pass items apply uniformly across P01-P10; the sixth # is topic-specific (mirrors this manifest's H1). The two must_pass=false # items reward mechanistic interpretation and MC-reproducibility metadata # without blocking proceed-vs-rerun on them. # --------------------------------------------------------------------------- requirements: - id: req_results_json type: artifact description: >- A canonical results.json file exists at the workspace root with at least the keys: primary_metric (number), metric_key (string), metrics (object with numeric keys), hypotheses (object with h1/h2/h3 entries each carrying a `supported` boolean), summary (non-empty string). must_pass: true - id: req_metrics_numeric type: numeric description: >- results.json metrics MUST contain at least 3 numeric (non-null, finite) values directly relevant to the headline physics observable named in the experiment_design.metrics list above — these are the numbers the paper will report in its Results section. must_pass: true - id: req_hypotheses_supported_flags type: discussion description: >- results.json hypotheses.h1/h2/h3 each MUST have an explicit `supported` boolean AND a `details` string ≥ 40 characters quoting the numerical evidence (specific values + their source artifact) used to reach the verdict. must_pass: true - id: req_publication_figure type: artifact description: >- At least one publication-quality figure file (PDF or PNG, ≥150 DPI for raster) exists under figures/ or output/figures/ with axes labeled in physical units (GeV / pb / fb / dimensionless) and a legend if multiple series are plotted. The figure must directly support a hypothesis verdict. must_pass: true - id: req_model_implementation type: artifact description: >- The BSM Lagrangian is implemented either as a FeynRules .fr file (models/*.fr) with a matching UFO directory (models/*_UFO/ containing at least particles.py, parameters.py, couplings.py, vertices.py), OR as analytic Python code that explicitly computes the cross sections from the Lagrangian terms. A pure SM baseline with no BSM piece is NOT sufficient. must_pass: true - id: req_lq_coupling_band type: numeric description: >- results.json metrics MUST report the 2σ combined ATLAS+CMS √(g_c* g_b) exclusion band at M_U1=1 TeV; the band lower edge must be in [0.21, 0.39] and the upper edge in [1.05, 1.95] (published [0.3, 1.5] ±30%). must_pass: true - id: req_mechanistic_writeup type: discussion description: >- The summary or structured_results section provides a one-paragraph mechanistic interpretation of WHY the headline observable comes out the way it does (which interference / propagator structure / cut effect drives the result). Nice-to-have, not blocking proceed. must_pass: false - id: req_mc_reproducibility type: discussion description: >- results.json or a sibling reproducibility section names: (a) the MadGraph5_aMC@NLO version, (b) the PDF set used (if applicable), (c) at least one explicit random seed. Required for full reproducibility but not for scientific correctness. must_pass: false