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| id: P02 |
| title: "Reproducing $pp \\to \\mu^\\pm N$ cross section vs heavy-Majorana-neutrino mass at $\\sqrt{s} = 7, 8, 14$ TeV" |
| arxiv_id: "1308.2209" |
| venue: "ARC-Bench Physics 2026" |
| paper_asset: null |
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| synthesis: | |
| Reproducing the LHC sensitivity to a single heavy Majorana neutrino $N$ |
| in the muon channel as a benchmark of the agent's ability to assemble a |
| hadron-collider Lagrangian -> MC -> analysis pipeline. The BSM extension |
| adds a right-handed singlet $N$ mixing with $\nu_\mu$ via the |
| dimensionless real parameter $V_{\mu N}$, so the relevant interaction is |
| $\mathcal{L}_N \supset -(g_2/\sqrt{2})\,V_{\mu N}\,(\bar\mu\gamma^\mu P_L |
| N)\,W^-_\mu + (\text{NC term}) + \text{h.c.}$ The diagnostic observable |
| is the $W^*$-mediated cross section $\sigma(pp \to \mu^\pm N)$ scanned |
| over $m_N \in \{100, 200, \ldots, 1000\}$ GeV with $|V_{\mu N}|=1$, at |
| three LHC energies $\sqrt{s} \in \{7, 8, 14\}$ TeV with the CTEQ6L PDF. |
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| A credible study (a) implements the heavy-Majorana-neutrino Lagrangian |
| (FeynRules .fr or analytic UFO modification), (b) sets up MadGraph runs |
| for the 30 (mass, energy) cells with the CTEQ6L PDF, (c) extracts the |
| cross section per cell, and (d) plots three side-by-side panels of |
| $\sigma(m_N)$ on a log-y axis over $[100,1000]$ GeV vs $[0.1, 4\times |
| 10^4]$ fb. Research question: *does the agent reproduce the steep |
| PDF-driven fall-off of $\sigma(pp \to \mu^\pm N)$ with $m_N$ and the |
| correct ordering between $\sqrt{s}=7$, 8, and 14 TeV predicted by |
| arXiv:1308.2209 Fig. 3?* |
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| hypotheses: |
| - id: H1 |
| statement: "At $m_N = 200$ GeV and $\\sqrt{s}=14$ TeV, $\\sigma(pp \\to \\mu^\\pm N)$ falls within $\\pm 30\\%$ of the published reference value." |
| measurable: true |
| - id: H2 |
| statement: "Cross-section ordering $\\sigma(14\\,\\mathrm{TeV}) > \\sigma(8\\,\\mathrm{TeV}) > \\sigma(7\\,\\mathrm{TeV})$ holds at every mass point, with the 14/7 ratio at $m_N = 500$ GeV in $[5, 30]$." |
| measurable: true |
| - id: H3 |
| statement: "$\\sigma(m_N)$ falls by at least 2 orders of magnitude between $m_N = 100$ GeV and $m_N = 1000$ GeV at every LHC energy." |
| measurable: true |
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| experiment_design: |
| research_question: "Does the agent reproduce the cross-section curves for $pp \\to \\mu^\\pm N$ as a function of the heavy-Majorana-neutrino mass at the 7, 8, and 14 TeV LHC, matching Figure 3 of arXiv:1308.2209?" |
| conditions: |
| - name: "lhc_7tev" |
| description: "$pp$ collisions at $\\sqrt{s}=7$ TeV with CTEQ6L PDF, mass scan $m_N \\in \\{100, 200, 300, 400, 500, 600, 700, 800, 900, 1000\\}$ GeV, $|V_{\\mu N}|=1$." |
| - name: "lhc_8tev" |
| description: "Same setup at $\\sqrt{s}=8$ TeV (LHC Run 1 final dataset energy)." |
| - name: "lhc_14tev" |
| description: "Same setup at $\\sqrt{s}=14$ TeV (HL-LHC design)." |
| baselines: |
| - "Charged-current SM $pp \\to \\mu \\nu_\\mu$ (W production) cross check at the same energies" |
| metrics: |
| - name: "cross_section_fb" |
| direction: "match_reference" |
| description: "Total $\\sigma(pp \\to \\mu^\\pm N)$ in fb at each (mass, energy) cell." |
| - name: "energy_ratio_14_to_7" |
| direction: "match_reference" |
| description: "$\\sigma(14\\,\\mathrm{TeV})/\\sigma(7\\,\\mathrm{TeV})$ at $m_N = 500$ GeV." |
| - name: "mass_dropoff_factor" |
| direction: "match_reference" |
| description: "$\\sigma(m_N=100)/\\sigma(m_N=1000)$ at each $\\sqrt{s}$." |
| datasets: |
| - process_id: "pp_to_muN_via_Wstar" |
| sqrt_s_TeV: 14 |
| description: "$pp \\to \\mu^\\pm N$ via $W^*$ at the LHC (CTEQ6L PDF). Three sub-samples for $\\sqrt{s} \\in \\{7,8,14\\}$ TeV." |
| compute_requirements: |
| gpu_required: false |
| estimated_wall_clock_sec: 3600 |
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| rubric_path: "experiments/arc_bench/config/physics/rubrics/P02.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_xsec_at_mN_200 |
| type: numeric |
| description: >- |
| results.json metrics MUST report a numeric `sigma_pp_to_muN_at_mN200_14TeV_fb` (or equivalent) within ±30% of the published reference value at m_N=200 GeV, √s=14 TeV. |
| 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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