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| id: P07 |
| title: "Reproducing the $m_{ej}$ resonance in $pp \\to \\mathrm{LQ} \\to ej$ via the LUXlep proton lepton PDF" |
| arxiv_id: "2005.06475" |
| venue: "ARC-Bench Physics 2026" |
| paper_asset: null |
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| synthesis: | |
| Reproducing the LHC sensitivity to a scalar leptoquark in the |
| $pp \to \mathrm{LQ} \to ej$ channel as a benchmark of the agent's |
| ability to assemble a full Lagrangian -> MC -> shower -> detector -> |
| analysis pipeline using a non-trivial PDF (LUXlep, with electrons inside |
| the proton). The Lagrangian |
| $\mathcal{L} = \lambda_{eu}\,\mathrm{LQ}_{eu}\,e_R^T i\sigma^2 u_R + |
| \mathrm{h.c.}$ describes an $SU(2)_L$-singlet, color-triplet, |
| $Q=-1/3$ scalar leptoquark coupling to a right-handed lepton-quark pair. |
| The diagnostic observable is the reconstructed invariant mass $m_{ej}$ |
| of the leading electron and leading jet, peaked at the input |
| $M_\mathrm{LQ}=3$ TeV with $\Gamma_\mathrm{LQ}=60$ GeV after Pythia8 + |
| Delphes ATLAS detector smearing. |
| |
| A credible study (a) implements the scalar-LQ Lagrangian (FeynRules .fr |
| + UFO), (b) generates 100k events at $\sqrt{s}=13$ TeV with the LUXlep |
| PDF (proton content redefined to include leptons + photon) and |
| generation cuts $p_T(\ell, j) > 500$ GeV, $|\eta| < 2.5$, (c) applies |
| the Pythia8 lepton-to-photon workaround (replace initial-state leptons |
| with photons in the LHE; set Check:event=off; shower; Delphes ATLAS |
| card with anti-$k_T$ R=0.4 jets; LHCO output), (d) selects events with |
| exactly one $e$ ($p_T>500$ GeV, $|\eta|<2.5$), one $j$ ($p_T>500$ GeV, |
| $|\eta|<2.5$), $E_T^\mathrm{miss} < 50$ GeV, lepton veto, jet veto, |
| (e) histograms $m_{ej}$ in 100 GeV bins from 0 to 5000 GeV weighted by |
| $\sigma\mathcal{L}/N_\mathrm{gen}$ at $\mathcal{L}=100$ fb$^{-1}$, and |
| (f) plots on log-y $[10^{-3}, 5\times 10^2]$ events/bin over [1000, |
| 5000] GeV. Research question: *does the agent reproduce the scalar-LQ |
| resonance peak at $m_{ej} \approx 3$ TeV from Figure 2 of arXiv:2005.06475?* |
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| hypotheses: |
| - id: H1 |
| statement: "Reconstructed $m_{ej}$ peaks within $\\pm 5\\%$ of the input $M_\\mathrm{LQ}=3000$ GeV after Pythia8+Delphes smearing (i.e., peak in [2850, 3150] GeV)." |
| measurable: true |
| - id: H2 |
| statement: "The generation-level $p_T(\\ell, j) > 500$ GeV cut yields $\\geq 50\\%$ acceptance for the benchmark $M_\\mathrm{LQ}=3$ TeV signal." |
| measurable: true |
| - id: H3 |
| statement: "Total event count in the [2.5, 3.5] TeV $m_{ej}$ window at $\\mathcal{L} = 100$ fb$^{-1}$ matches the published value within $\\pm 30\\%$." |
| measurable: true |
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| experiment_design: |
| research_question: "Does the agent reproduce the $m_{ej}$ invariant-mass distribution for $pp \\to \\mathrm{LQ} \\to ej$ at $\\sqrt{s}=13$ TeV with LUXlep PDF and $M_\\mathrm{LQ}=3$ TeV (Figure 2 of arXiv:2005.06475)?" |
| conditions: |
| - name: "lq_3tev_lambda1" |
| description: "Scalar LQ at $M_\\mathrm{LQ}=3000$ GeV, $\\Gamma_\\mathrm{LQ}=60$ GeV, $\\lambda_{eu}=1$, 100k events at $\\sqrt{s}=13$ TeV, LUXlep PDF, $p_T > 500$ GeV gen cuts, Pythia8 + Delphes ATLAS, LHCO output." |
| - name: "lq_2tev_check" |
| description: "Cross-check at $M_\\mathrm{LQ}=2000$ GeV with $\\lambda_{eu}=1$, same setup; verify that $m_{ej}$ peak shifts to 2 TeV." |
| baselines: |
| - "Background-only sanity check: $\\lambda_{eu}=0$ (LQ decoupled) should produce zero $m_{ej}$ events above the gen-level cut" |
| metrics: |
| - name: "peak_position_gev" |
| direction: "match_reference" |
| description: "Bin-center of the maximum of the reconstructed $m_{ej}$ histogram for the 3 TeV signal." |
| - name: "acceptance_pt500" |
| direction: "match_reference" |
| description: "Fraction of generated events with both lepton and jet $p_T > 500$ GeV at $M_\\mathrm{LQ}=3$ TeV." |
| - name: "integrated_yield_in_window" |
| direction: "match_reference" |
| description: "Sum of weighted events in $m_{ej} \\in [2500, 3500]$ GeV at $\\mathcal{L}=100$ fb$^{-1}$." |
| datasets: |
| - process_id: "pp_to_LQ_to_ej_LUXlep" |
| sqrt_s_TeV: 13 |
| description: "Single resonant scalar leptoquark production via lepton-quark fusion using LUXlep proton PDF." |
| compute_requirements: |
| gpu_required: false |
| estimated_wall_clock_sec: 3600 |
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| rubric_path: "experiments/arc_bench/config/physics/rubrics/P07.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_mej_peak_position |
| type: numeric |
| description: >- |
| results.json metrics MUST report the reconstructed m_ej peak position (after Pythia8+Delphes smearing) in the interval [2850, 3150] GeV (input M_LQ=3 TeV ±5%). |
| 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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