{
  "abstract": "Top-quark spin correlations provide a direct probe of the quantum numbers of a resonance decaying to $t\\bar t$. We compare a CP-odd type-II two-Higgs-doublet-model pseudoscalar $A$ with a spin-1 leptophobic topcolor $Z'$ in the dilepton channel. The two hypotheses differ in the parton-level helicity correlation by $Δc_{\\rm hel}\\simeq0.43$, nearly independently of mass, and neutrino-weighted reconstruction preserves this separation with an effective dilution factor of about 0.66. At 400 and 800 GeV, the pseudoscalar normalization is anchored to CMS HIG-22-013 coupling limits, while the $Z'$ rate is matched to the pseudoscalar so that the comparison primarily tests spin structure. The leading-order $t\\bar t$-only projection gives expected separations of 2.27 and 2.74 standard deviations at $3000\\,{\\rm fb}^{-1}$. Equalizing the selected signal yields gives pure spin-shape separations of 1.86 and 2.70 standard deviations. Profiling a Gaussian-constrained Standard Model $c_{\\rm hel}$-shape nuisance gives 2.07 and 2.63 standard deviations for an optimistic sideband benchmark, or 1.67 and 2.26 for a weaker constraint. A local fixed-template extrapolation corresponds to five-standard-deviation discrimination at couplings about 22\\% and 16\\% above the reference values. A 1500 GeV $g=1$ point is shown separately. The reach is limited by the sub-percent signal fraction and control of the mass-dependent Standard Model spin shape, rather than by the intrinsic resonance-spin separation.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.11641",
  "author_total": 2,
  "authors": [
    {
      "name": "Ahmed Bellagroudi"
    },
    {
      "name": "Farida Fassi"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/4wz2ekj0de3j8.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.11641",
  "fulltext_url": null,
  "id": "4wz2ekj0de3j8",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.11641",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "hep-ph"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2609.11641",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-10",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/4wz2ekj0de3j8.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:20:26Z",
      "native_id": "2609.11641",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.11641"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:hep-ph",
      "subfield": "high-energy"
    }
  ],
  "title": "Distinguishing a pseudoscalar from a vector $t\\bar t$ resonance with top-quark spin correlations at the HL-LHC",
  "title_text": "Distinguishing a pseudoscalar from a vector tt̅ resonance with top-quark spin correlations at the HL-LHC",
  "type": "preprint",
  "updated_at": "2026-10-30T12:20:26Z",
  "url": "https://research.draconitic.com/paper/4wz2ekj0de3j8",
  "venue": "arXiv",
  "versions": []
}