{
  "abstract": "We use lattice gauge theory to investigate the Peskin-Takeuchi S parameter in SU(3) gauge theory with eight light fundamental fermions (eight-flavor QCD), a candidate for walking technicolor. We develop a new approach to computing S using the first time moment of current correlators, in addition to the conventional vacuum-polarization method, and obtain consistent results. Finite-volume (FV) corrections are estimated using data at multiple lattice volumes and a formula motivated by chiral perturbation theory. At the smallest fermion mass, the one-doublet contribution is S = 0.281(5)(17), smaller than the value $\\sim 0.35$ in scaled-up 2+1-flavor QCD (without subtracting the SM contribution). However, contrary to naive expectations, S toward smaller fermion masses is not necessarily suppressed once FV corrections are included. The resulting Gasser-Leutwyler parameter $L_{10}^r(M_ρ)$ is similar to that in real-world QCD. We also determine the vector and axial-vector meson decay constants, $F_ρ$ and $F_{a_1}$. The ratio $F_ρ/F_π$ is stable against the fermion mass and consistent with the KSRF estimate, implying a $ρππ$ coupling similar to that in real-world QCD. We predict the techni-rho decay width into weak bosons to be $Γ_ρ/M_ρ\\lesssim 0.24/N$, where N is the number of weak doublets. We further find that the rho- and $a_1$-dominated Weinberg spectral-function and Das-Mathur-Okubo sum rules are satisfied, yielding S and $L_{10}^r(M_ρ)$ consistent with our main results. We discuss implications for BSM model building.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.35371",
  "author_total": 10,
  "authors": [
    {
      "name": "Yasumichi Aoki"
    },
    {
      "name": "Tatsumi Aoyama"
    },
    {
      "name": "Ed Bennett"
    },
    {
      "name": "Toshihide Maskawaa"
    },
    {
      "name": "Kohtaroh Miura"
    },
    {
      "name": "Hiroshi Ohki"
    },
    {
      "name": "Enrico Rinaldi"
    },
    {
      "name": "Akihiro Shibata"
    },
    {
      "name": "Koichi Yamawaki"
    },
    {
      "name": "Takeshi Yamazaki"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/c3027bfy92exh.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.35371",
  "fulltext_url": null,
  "id": "c3027bfy92exh",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.35371",
  "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-lat"
    ],
    [
      "openalex",
      "3106|Quantum Chromodynamics and Particle Interactions"
    ]
  ],
  "openalex": "W7214715408",
  "pdf_url": "https://arxiv.org/pdf/2609.35371",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-28",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/c3027bfy92exh.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:25:12Z",
      "native_id": "2609.35371",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.35371"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:hep-lat",
      "subfield": "high-energy"
    }
  ],
  "title": "The Peskin-Takeuchi $S$ parameter and vector meson decay constants in $N_f=8$ QCD",
  "title_text": "The Peskin-Takeuchi S parameter and vector meson decay constants in N_f=8 QCD",
  "type": "preprint",
  "updated_at": "2026-10-30T12:25:12Z",
  "url": "https://research.draconitic.com/paper/c3027bfy92exh",
  "venue": "arXiv",
  "versions": []
}