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| id: P03 |
| title: "Reproducing 8 TeV LHC dilepton exclusion contours for a B-L Z' boson with kinetic mixing" |
| arxiv_id: "1605.02910" |
| venue: "ARC-Bench Physics 2026" |
| paper_asset: null |
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| synthesis: | |
| Reproducing the LHC Run 1 sensitivity to a B-L gauge boson Z' with |
| kinetic mixing as a benchmark of the agent's ability to combine MC |
| parameter scans with an analytic statistical recast. The model has a |
| Z' coupling to SM fermions via a left/right combination |
| $C_{f,L/R}(\tilde g, g_1', M_{Z'})$ where $g_1'$ is the B-L gauge |
| coupling, $\tilde g$ is the kinetic mixing, and the production cross |
| section is the exact quadratic form |
| $\sigma(pp \to Z') = A g_1'^2 + B g_1' \tilde g + C \tilde g^2$ — so |
| three runs per mass point determine $(A,B,C)$ for the entire $(\tilde |
| g, g_1')$ plane. The diagnostic observable is the three-panel exclusion |
| contour at $\mathrm{Sig}\equiv 2(\sqrt{S+B}-\sqrt B) = 2$ for |
| $M_{Z'} \in \{2.0, 2.5, 3.0\}$ TeV at $\mathcal{L} = 20$ fb$^{-1}$. |
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| A credible study (a) implements the kinetic-mixing B-L Lagrangian and |
| $C_{f,L/R}$ couplings, (b) runs the 9 signal MadGraph runs (3 mass |
| points x 3 coupling points) plus 3 SM Drell-Yan background runs with |
| $m_{\ell\ell} > 0.9 M_{Z'}$ generator cut, (c) computes the analytic |
| $Z' \to e^+e^- + \mu^+\mu^-$ branching ratio including 3 degenerate |
| heavy Majorana neutrinos $m_{\nu_h}=95$ GeV, (d) applies the published |
| NNLO k-factors $k\in\{1.35,1.40,1.50\}$ and acceptance |
| $\epsilon_\mathrm{acc}=0.6$, (e) solves the $\mathrm{Sig}=2$ equation |
| on a 2D grid in $(\tilde g, g_1')$, and (f) plots three side-by-side |
| contours. Research question: *does the agent reproduce the three-panel |
| $(\tilde g, g_1')$ exclusion contours at $M_{Z'}=2.0, 2.5, 3.0$ TeV from |
| Figure 1 of arXiv:1605.02910?* |
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| hypotheses: |
| - id: H1 |
| statement: "For the $M_{Z'}=2$ TeV panel, the exclusion contour crosses the $\\tilde g = 0$ axis at $g_1' \\in [0.10, 0.20]$ (matching the published value within 30%)." |
| measurable: true |
| - id: H2 |
| statement: "The $(A, B, C)$ quadratic coefficients extracted at $M_{Z'}=2$ TeV satisfy $A > 0$ and $|B| \\le 4\\sqrt{AC}$ (positivity of the cross section over the full parameter plane)." |
| measurable: true |
| - id: H3 |
| statement: "The maximum reach in $g_1'$ at $\\tilde g = 0$ degrades by at least a factor of 2 going from $M_{Z'}=2$ TeV to $M_{Z'}=3$ TeV, reflecting the PDF suppression at high mass." |
| measurable: true |
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| experiment_design: |
| research_question: "Does the agent reproduce the three-panel $(\\tilde g, g_1')$ 2$\\sigma$ exclusion contours at $M_{Z'}=2.0, 2.5, 3.0$ TeV from the LHC Run 1 dilepton search at $\\sqrt{s}=8$ TeV with $\\mathcal{L}=20$ fb$^{-1}$ (Figure 1 of arXiv:1605.02910)?" |
| conditions: |
| - name: "mzp_2tev" |
| description: "$M_{Z'}=2$ TeV: 3 signal runs at $(g_1', \\tilde g) \\in \\{(0.10, 0), (0.10, -0.10), (0.15, -0.05)\\}$." |
| - name: "mzp_2p5tev" |
| description: "$M_{Z'}=2.5$ TeV: 3 signal runs at the same three $(g_1', \\tilde g)$ points." |
| - name: "mzp_3tev" |
| description: "$M_{Z'}=3$ TeV: 3 signal runs at $(g_1', \\tilde g) \\in \\{(0.30, 0), (0.30, -0.30), (0.50, -0.60)\\}$." |
| baselines: |
| - "SM Drell-Yan $pp \\to \\ell^+\\ell^-$ at $\\sqrt{s}=8$ TeV with generator-level cut $m_{\\ell\\ell} > 0.9 M_{Z'}$, one per mass point" |
| metrics: |
| - name: "exclusion_g1p_at_kinmix0" |
| direction: "match_reference" |
| description: "Value of $g_1'$ at which the $\\mathrm{Sig}=2$ contour crosses $\\tilde g = 0$, per mass point." |
| - name: "quadratic_coefficients_ABC" |
| direction: "match_reference" |
| description: "$(A, B, C)$ extracted from the 3 signal runs per mass; positive-definite check." |
| - name: "br_zprime_to_dilepton" |
| direction: "match_reference" |
| description: "Analytic $\\mathrm{BR}(Z' \\to e^+e^-+\\mu^+\\mu^-)$ at the three benchmark masses." |
| datasets: |
| - process_id: "pp_to_Zprime_BL_kinmix" |
| sqrt_s_TeV: 8 |
| description: "$pp \\to Z'$ with kinetic-mixing B-L Z' at the LHC, dilepton final state. Background: SM Drell-Yan with $m_{\\ell\\ell}$ cut." |
| compute_requirements: |
| gpu_required: false |
| estimated_wall_clock_sec: 3600 |
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| rubric_path: "experiments/arc_bench/config/physics/rubrics/P03.json" |
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| 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 |
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|
| - 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 |
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| - 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 |
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|
| - 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 |
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| - 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 |
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| - id: req_g1prime_threshold |
| type: numeric |
| description: >- |
| results.json metrics MUST report the g1' coordinate where the 2σ exclusion contour at M_Z'=2 TeV crosses the g̃=0 axis, in the interval [0.07, 0.26] (i.e. published [0.10, 0.20] ±30%). |
| must_pass: true |
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|
| - 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 |
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| - 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 |
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